AT-401-B - Owner Manual

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<p>AT-401</p><p>SERIES</p><p>OWNER'S</p><p>MANUAL</p><p>OWNERS MANUALOWNERS MANUALOWNERS MANUALOWNERS MANUALOWNERS MANUAL</p><p>AIR TRACTOR MODEL AT-401AIR TRACTOR MODEL AT-401AIR TRACTOR MODEL AT-401AIR TRACTOR MODEL AT-401AIR TRACTOR MODEL AT-401</p><p>AGRICULTURAL AIRPLANEAGRICULTURAL AIRPLANEAGRICULTURAL AIRPLANEAGRICULTURAL AIRPLANEAGRICULTURAL AIRPLANE</p><p>Description</p><p>Operation</p><p>Maintenance</p><p>Inspection</p><p>Lubrication</p><p>Repairs</p><p>Service Letters</p><p>Radial Engine Tune Up</p><p>NOTE: This Manual Is ApplicableNOTE: This Manual Is ApplicableNOTE: This Manual Is ApplicableNOTE: This Manual Is ApplicableNOTE: This Manual Is Applicable</p><p>To Model AT-401BTo Model AT-401BTo Model AT-401BTo Model AT-401BTo Model AT-401B</p><p>Air Tractor, Inc. Owners Manual</p><p>Olney, Texas Last Revised: 12/10/19</p><p>LIST OF EFFECTIVE PAGES</p><p>AT-401 OWNERS MANUAL</p><p>PAGE</p><p>NUMBER DATE DATE DATE DATE DATE</p><p>Description</p><p>1 9/15/89 5/26/95 8/20/97 4/1/98 4/20/05</p><p>2 9/15/89 4/1/98</p><p>3 9/15/89 4/1/98</p><p>4 9/15/89 5/2/94 4/1/98</p><p>5 9/15/89 5/2/94 4/1/98</p><p>6 9/15/89 5/2/94 4/1/98</p><p>7 9/15/89 5/2/94 4/1/98</p><p>8 9/15/89 5/2/94 4/1/98</p><p>9 9/15/89 5/2/94 4/1/98 1/12/09</p><p>10 5/2/94 4/1/98</p><p>11 4/1/98</p><p>12 4/1/98</p><p>Operations</p><p>1 9/15/89</p><p>2 9/15/89</p><p>3 9/15/89 5/2/94</p><p>4 9/15/89 5/2/94</p><p>5 9/15/89</p><p>6 9/15/89 4/1/98</p><p>7 9/15/89 4/1/98</p><p>8 9/15/89</p><p>9 9/15/89</p><p>10 9/15/89</p><p>11 9/15/89</p><p>12 9/15/89</p><p>Maintenance</p><p>1 9/15/89 7/13/11</p><p>2 9/15/89 5/2/94</p><p>3 9/15/89 5/2/94</p><p>4 9/15/89 5/2/94 4/1/98</p><p>5 9/15/89 5/2/94 4/1/98</p><p>6 9/15/89 5/2/94</p><p>7 9/15/89</p><p>8 9/15/89 5/2/94 4/1/98</p><p>9 9/15/89 5/2/94 4/1/98</p><p>Air Tractor, Inc. Owners Manual</p><p>Olney, Texas Last Revised: 12/10/19</p><p>LIST OF EFFECTIVE PAGES</p><p>AT-401 OWNERS MANUAL</p><p>(Continued)</p><p>PAGE</p><p>NUMBER DATE DATE DATE DATE DATE</p><p>Maintenance (Continued)</p><p>10 9/15/89 5/2/94 4/1/98</p><p>11 9/15/89 5/2/94 4/1/98 3/30/03</p><p>12 9/15/89 4/1/98 4/20/05 9/16/09</p><p>13 9/15/89 5/2/94 4/1/98 9/16/09</p><p>14 9/15/89</p><p>15 9/15/89 5/2/94 4/1/98</p><p>16 9/15/89</p><p>17 9/15/89 4/1/98</p><p>18 9/15/89</p><p>19 9/15/89 4/1/98</p><p>20 9/15/89 5/2/94</p><p>21 9/15/89 5/2/94 4/1/98</p><p>22 9/15/89 5/2/94 4/1/98 8/10/03</p><p>23 9/15/89 5/2/94 4/1/98 6/26/00</p><p>24 9/15/89 5/2/94 4/1/98</p><p>25 9/15/89 5/2/94 4/1/98</p><p>26 9/15/89 5/2/94</p><p>27 9/15/89 5/2/94 4/1/98</p><p>28 9/15/89 5/2/94 4/1/98</p><p>29 9/15/89 5/2/94 4/1/98</p><p>30 9/15/89 5/2/94 4/1/98 7/13/11</p><p>31 9/15/89 5/2/94 4/1/98</p><p>32 9/15/89 5/2/94 4/1/98</p><p>33 9/15/89 5/2/94 4/1/98</p><p>34 9/15/89 5/2/94 4/1/98 4/20/05</p><p>35 9/15/89 5/2/94 4/1/98 4/20/05 7/13/11</p><p>35A 4/20/05 7/13/11</p><p>35B 4/20/05</p><p>36 9/15/89 5/2/94 4/1/98</p><p>37 5/2/94 4/1/98</p><p>38 4/1/98</p><p>39 4/1/98</p><p>40 4/1/98</p><p>41 4/1/98 4/20/05</p><p>42 4/1/98 1/12/09 9/16/09 2/9/12</p><p>43 4/1/98 1/12/09 7/13/11 2/9/12</p><p>44 1/12/09 7/13/11 2/9/12</p><p>45 7/13/11 2/9/12</p><p>Air Tractor, Inc. Owners Manual</p><p>Olney, Texas Last Revised: 12/10/19</p><p>LIST OF EFFECTIVE PAGES</p><p>AT-401 OWNERS MANUAL</p><p>(Continued)</p><p>PAGE</p><p>NUMBER DATE DATE DATE DATE DATE</p><p>Inspection</p><p>1 9/15/89 5/2/94 4/1/98 3/30/03</p><p>2 9/15/89 4/1/98</p><p>3 9/15/89</p><p>4 9/15/89 5/2/94 4/1/98</p><p>5 9/15/89 4/1/98 3/30/03</p><p>6 9/15/89 4/1/98 3/30/03 2/1/06 12/10/19</p><p>7 5/2/94 4/1/98 6/26/00 8/10/03 1/12/09</p><p>2/9/12</p><p>Lubrication</p><p>1 9/15/89</p><p>2 9/15/89</p><p>Repairs</p><p>1 9/15/89 5/2/94</p><p>2 9/15/89 4/1/98</p><p>3 9/15/89</p><p>Figures</p><p>1-24 2/9/12</p><p>AIR TRACTOR, INCAIR TRACTOR, INCAIR TRACTOR, INCAIR TRACTOR, INCAIR TRACTOR, INC</p><p>Olney, TexasOlney, TexasOlney, TexasOlney, TexasOlney, Texas</p><p>AT-401AT-401AT-401AT-401AT-401</p><p>TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS</p><p>DESCRIPTION SECTIONDESCRIPTION SECTIONDESCRIPTION SECTIONDESCRIPTION SECTIONDESCRIPTION SECTION</p><p>Page No.Page No.Page No.Page No.Page No.</p><p>General 1</p><p>Certification Basis 1</p><p>Fuselage 1</p><p>Wings 1</p><p>Ailerons 2</p><p>Flaps 2</p><p>Empennage 2</p><p>Landing Gear and Brakes 3</p><p>Engine 3</p><p>Fuel System 4</p><p>To Install Ferry Fuel System 5</p><p>To Remove Ferry Fuel System 5</p><p>Fuel System Schematic 6</p><p>Engine Controls 7</p><p>Optional Equipment 7</p><p>Propeller and Governors 8</p><p>Electrical System 8</p><p>Cockpit 9</p><p>Control System 9</p><p>Brake System 10</p><p>Dispersal System 10</p><p>Brake System Schematic 11</p><p>Hopper Rinse System 12</p><p>GENERALGENERALGENERALGENERALGENERAL</p><p>The Air Tractor AT-401 is an all metal cantilever low wing monoplane designed especially for</p><p>agricultural operations. It is powered by a Pratt & Whitney R1340 radial engine having a take-off</p><p>rating of 600 horsepower. The propeller is a Hamilton Standard two-blade 108" diameter constant</p><p>speed prop. The hopper is made of fiberglass and has a 400 U.S. gallon capacity. The horizontal</p><p>stabilizer is all-metal and strut braced for added rigidity. The fuselage features removable skin</p><p>panels for ease of maintenance and cleaning. The rudder and elevators are of all-metal construc-</p><p>tion and sealed to prevent chemical entry. High-lift flaps are incorporated and are interconnected</p><p>with the ailerons to provide short take-off and landing distances.</p><p>CERTIFICATION BASISCERTIFICATION BASISCERTIFICATION BASISCERTIFICATION BASISCERTIFICATION BASIS</p><p>The AT-401 is structurally certificated to meet the requirements of FAR 23. The engine</p><p>installation along with the systems and equipment meet CAM 8 requirements. The AT-401 is</p><p>certificated by the manufacturer for a gross weight of 6,000 lbs. However, under the provisions of</p><p>Part 8 the operator may select his own maximum operating weight, the field experience shows</p><p>that operating weights of up to 7,800 lbs. can be carried safely with adequate margins of</p><p>performance and structural strength. Starting with serial number 401B-1015, 401B-1021 and</p><p>subsequent, the certified gross weight has been increased to 7,000 pounds, providing the p/n</p><p>40059-21 (AT-402A) main landing gear is installed. These later models with the AT-402A landing</p><p>gear may be operated at higher operating weights selected by the operator.</p><p>FUSELAGEFUSELAGEFUSELAGEFUSELAGEFUSELAGE</p><p>The fuselage structure is of heli-arc welded 4130N steel tubing. All fittings and bushings are</p><p>also of 4130N steel. Fuselage repairs may be made in accordance with appropriate FAA repair</p><p>procedures and gas welding is permissible. There are no heat-treated members of the fuselage.</p><p>The front section of the fuselage from the rear spar forward and including the engine mount have</p><p>been oven stress-relieved in order to prevent stress concentrations from the welding operation.</p><p>For corrosion control oil passage holes are drilled at the intersections of all tubes and clusters.</p><p>Hot oil is then pumped into the fuselage frame and drained. This oil is Linseed Oil and adheres to</p><p>the inside walls of the tubing. The exterior of the fuselage frame is then sand-blasted and painted</p><p>with Ag Air yellow epoxy which is resistant to nearly all chemical action.</p><p>The fuselage lower and upper skins are attached to the fuselage frame with stainless screws</p><p>and nuts. The fuselage side panels are of heavy gauge 2024T3 alclad and are attached to</p><p>stainless camloc receptacles. This allows the side panels to be removed in minutes, leaving the</p><p>fuselage frame open for thorough cleaning and inspection. All skins are mounted with clearance</p><p>between the skin and the fuselage tubing so that chemicals will not collect and cause corrosion.</p><p>WINGSWINGSWINGSWINGSWINGS</p><p>The wing structure is full cantilever, with the main spar carrying all of the bending loads.</p><p>Construction is of 2024T3 alclad for skins and spar webs. The upper spar cap is also 2024T3</p><p>material, but the lower spar cap is made of alloy steel. The wing has a constant chord of 72</p><p>inches and a span of 51.0 ft. The wing utilizes a NACA 4415 wing section and has 2 degrees of</p><p>washout twist.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Description Page 1Description Page 1Description Page 1Description Page 1Description Page 1</p><p>AT-401AT-401AT-401AT-401AT-401</p><p>over these lines should be executed</p><p>smoothly, and parallel passes made along them to ensure complete coverage.</p><p>One should always remember that if there are power lines leading into a house or building,</p><p>it is quite possible that one or more telephone wires may be strung beneath them. Phone lines are</p><p>almost always made of steel, and although of small diameter, they are sometimes quite hard for</p><p>an airplane to break, and may stretch a great deal before they do. If one is low enough on his</p><p>initial pass, he will see them silhouetted against the sky in time to climb and avoid them.</p><p>When two aircraft are flying the same field together, they should space their passes so that</p><p>lingering turbulence from one will not be a hazard to the other, especially near the field bounda-</p><p>ries. When the wing’s angle of attack is sharply increased, as in a quick pullup, a very strong</p><p>rolling vortex can be generated which may be a cause of concern to the following aircraft near the</p><p>point of wire passage, as any deviation from level flight is especially hazardous at this point.</p><p>During the months of March and September, it is important to plan one’s work so as to</p><p>avoid east and west passes near sunup or sundown, since the glare from the sun directly in front</p><p>of the aircraft will greatly increase the chances of collision with any obstacle which happens to be</p><p>in the flight path.</p><p>Steel tower transmission lines in the field are normally flown under in all but the most</p><p>extreme cases, since risks in a climb to a height of one hundred or more feet in order to clear</p><p>these objects are far more threatening than flight beneath them. If it is necessary to climb over</p><p>these cables because of low wires or other obstacles in their vicinity, it is highly recommended</p><p>Operations Page 10Operations Page 10Operations Page 10Operations Page 10Operations Page 10 Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.</p><p>September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989 AT-401AT-401AT-401AT-401AT-401</p><p>that the aircraft be lightly loaded and the pullup started at a very conservative distance away so</p><p>as not to run out of airspeed directly over the lines. If this action is necessary, many passes must</p><p>be made parallel to the towers. Certain of these lines have a ground wire stretched tightly along</p><p>the very top of the pylons, something to remember if one is tempted to cross them lower than the</p><p>towers at the position of maximum line droop. Pilots should be very much aware of wind direction</p><p>while making turns in the vicinity of these cables, as an aircraft can easily be blown into them by</p><p>winds which are higher at turn altitude than on the ground.</p><p>“Low-Viz” Conditions“Low-Viz” Conditions“Low-Viz” Conditions“Low-Viz” Conditions“Low-Viz” Conditions</p><p>No one should ever find himself in the position of having to cross a line of steel towers under</p><p>conditions of such limited visibility that the tops are obscured, thus having no choice but to go</p><p>under them. This indicates a lack of planning and judgement to say the least, but if a pilot should</p><p>find himself in this predicament his chances of a successful crossing will be improved if he turns</p><p>so as to apporach the lines at a very shallow angle. Using this method, they will not make a</p><p>surprise appearance over the nose dead ahead, and their closing speed with the airplane will be</p><p>much slower than with a ninety-degree approach, giving some valuable additional time in which</p><p>to pick a point to cross under safely.</p><p>In some areas it is required that treatment of crops be accomplished at night, and though</p><p>this would seem to make wire avoidance more difficult than during daylight hours, the actual</p><p>hazard does not seem to be any greater if proper care is taken in the planning and execution of</p><p>the job.</p><p>A knowledge of the entire working region is necessary for safety in the dark, and no pilot</p><p>should be flying closer than two miles to an area in which he is not aware of the location of every</p><p>obstruction over fifty feet in height, including the altitude and orientation of all tower lines.</p><p>If a thorough field inspection is desirable during the day, it should be mandatory at night,</p><p>and can be accomplished from a safe height using both turn and field lights to ascertain the</p><p>definite location of all obstructions. It is helpful to have one field light pointed down slightly lower</p><p>than the other to better illuminate the lines and poles when approaching over them. Good</p><p>working lights will show obstacles, including poles, up to one half mile away, and many lines</p><p>show up better under the lights than during the day. Most wires which can be flown under safely</p><p>in daylight can also be flown under at night, but those with marginal clearance are better flown</p><p>over.</p><p>Night ferry flights should be flown at an altitude which allows a wide margin of clearance for</p><p>all ground obstacles, again keeping in mind the location and direction of steel towers and other</p><p>high obstructions. An operating altimeter is essential for safe flight after dark, and should be</p><p>reset at zero at each new work location so as to indicate height above ground as accurately as</p><p>possible.</p><p>When You Do Hit OneWhen You Do Hit OneWhen You Do Hit OneWhen You Do Hit OneWhen You Do Hit One</p><p>The more time one spends in flight beneath pole height in close proximity to wires, cables,</p><p>and lines the greater is his chance of sooner or later making contact with one of these objects,</p><p>regardless of his skill or experience level. His actions during the first seconds after this unfortu-</p><p>nate event can make the difference between a front page story in the next day’s paper, or a</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Operations Page 11Operations Page 11Operations Page 11Operations Page 11Operations Page 11</p><p>AT-401AT-401AT-401AT-401AT-401 September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989</p><p>routine notation in the log of a wire repair crew.</p><p>After striking a wire, the first action a pilot must take is the immediate addition of maxi-</p><p>mum power while he still has flying speed and control of the aircraft. There is always the</p><p>possibility that he may be carrying hundreds of feet of copper or steel line streaming out and</p><p>down behind the aircraft, and immediate full power could mean the difference between continued</p><p>flight or loss of airspeed and an unmanageable descent. He should not hesitate to dump all or a</p><p>portion of his load as necessary to maintain flight, except in the case of dusting sulfur, where the</p><p>fire hazard associated with this substance will make it preferable to retain it in the aircraft.</p><p>If the pilot is clear of other wires ahead, and able to gain altitude, he should by all means</p><p>climb, as increased height lessens the chances of the attached wire dragging over other lines,</p><p>thus shorting them out and possibly adding their drag to the burden already being carried.</p><p>Upon reaching a safe altitude, the pilot should level and stabilize the airplane, inspect all</p><p>surfaces visible from the cockpit, and check its flying characteristics with a view towards landing</p><p>as soon as practicable. If he is indeed carrying a length of wire, he must plan his approach and</p><p>touchdown with this factor very much in mind. He should also survey the site of the strike for</p><p>possible injuries to flaggers or other ground personnel, and check the area for fires which may</p><p>have been started by the broken line.</p><p>Using judgement, planning, and common sense, it is quite possible for an agricultural</p><p>aviator to fly for very long periods of time without a wirestrike, and I sincerely hope that this text</p><p>contains information which may be useful to other pilots in achieving this goal.</p><p>Operations Page 12Operations Page 12Operations Page 12Operations Page 12Operations Page 12 Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.</p><p>September 15, 1989September 15, 1989September 15,</p><p>1989September 15, 1989September 15, 1989 AT-401AT-401AT-401AT-401AT-401</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.</p><p>Olney, TexasOlney, TexasOlney, TexasOlney, TexasOlney, Texas</p><p>AT-401AT-401AT-401AT-401AT-401</p><p>TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS</p><p>MAINTENANCE SECTIONMAINTENANCE SECTIONMAINTENANCE SECTIONMAINTENANCE SECTIONMAINTENANCE SECTION</p><p>Page No.Page No.Page No.Page No.Page No.</p><p>Fuel Requirements 1</p><p>Oil Requirements 1</p><p>Tire Inflation 1</p><p>Lifting and Jacking 1</p><p>Main Wheels 2</p><p>Main Wheel Alignment 2</p><p>Brakes 3</p><p>Brake Master Cylinders 4</p><p>Brake Bleeding 4</p><p>Parking Brake 5</p><p>Tail Wheel 5</p><p>Tail Wheel Fork 6</p><p>Tail Wheel Fork Housing 6</p><p>Tail Wheel Lock Pin and Housing 7</p><p>Main and Tail Gear Attach Bolts 7</p><p>Tail Gear Spring 8</p><p>Main Gear Spring 9</p><p>Wings 11</p><p>Wing Attachment to Fuselage 11</p><p>Wing Center Splice Connection 12</p><p>Wing Walk 13</p><p>Fuel Tanks 13</p><p>Fuel Tank Senders 14</p><p>Fuel Tank Receiver 15</p><p>Fuel System Drains 15</p><p>Fuel System Screens and Filters 16</p><p>Fuel Wobble Pump 16</p><p>Ailerons 16</p><p>Flaps 17</p><p>Aileron and Flap Rigging 18</p><p>Aileron and Flap Bellcranks & Supports 18</p><p>Flap Actuator 19</p><p>Flap Actuator Trouble Shooting 20</p><p>Flap Motor Trouble Shooting 22</p><p>Horizontal Stabilizers 22</p><p>Stabilizer Struts 23</p><p>Stabilizer Rigging 23</p><p>Vertical Fin 24</p><p>Rudder 24</p><p>Rudder Controls 24</p><p>Elevators 25</p><p>AIR TRACTOR, INC.</p><p>Olney, Texas</p><p>AT -401</p><p>TABLE OF CONTENTS</p><p>MAINTENANCE SECTION</p><p>(Cont i nued)</p><p>Elevator Controls 26</p><p>Cockpit Controls 27</p><p>Elevator Tr im Tabs 27</p><p>Tr im Tab Controls 28</p><p>Tr im Lever 28</p><p>Fuselage Removable Sk ins 28</p><p>Fuselage Fixed Sk ins 29</p><p>Fuselage Cockpit Sk ins 29</p><p>Fuselage Frame 29</p><p>Windshield 29</p><p>Canopy Doors 30</p><p>Seat 30</p><p>Hopper 31</p><p>Hopper Gate Box 31</p><p>Hopper Lid 31</p><p>Gate Box Controls 31</p><p>Spray Lever Controls 32</p><p>Spray Pump 32</p><p>Spray Plumbing 32</p><p>Bot tom Loading Plumbing 33</p><p>Spray Nozzles 33</p><p>Str ipping and Re-paint ing Par ts 34</p><p>Pr iming Aluminum Par ts with Chromated Alkyd Pr imer 35</p><p>Str ipping and Repaint ing Steel Par ts 35A</p><p>Mater ials Used for Str ipping, Paint ing, and Preservat ion 35A</p><p>Torque Values for Shop Use 36</p><p>Electr ical System Trouble Shoot ing 36</p><p>Light ing System Trouble Shoot ing 37</p><p>Elect r ical System Descr ipt ion 39</p><p>Airspeed System 41</p><p>Avionics 42</p><p>Life-Limited Items 42</p><p>Tie-Down Inst ruct ion 43</p><p>Towing Inst ruct ions and Limitat ions 44</p><p>AmSafe Airbag System 44</p><p>Check ing the Bat ter ies 45</p><p>Leveling 45</p><p>Weight and Balance 45</p><p>Air Tractor, Inc. Maintenance Page 1</p><p>AT-401 July 13, 2011</p><p>FUEL REQUIREMENTS</p><p>Fuel type for the AT-401 is aviation grade 80/87 minimum octane gasoline. If this fuel is not</p><p>available, use the next highest grade aviation gasoline, up to and including 100 octane. Under no</p><p>circumstances should aeromatic fuel be used.</p><p>OIL REQUIREMENTS</p><p>For summer flying SAE 60 grade oil should be used. For winter flying SAE 50 grade oil is</p><p>recommended. Select a well known aviation oil that is non-detergent and do not mix brands.</p><p>It is recommended that the oil level on the dipstick be maintained above 4 gallons at all</p><p>times. For extreme conditions the engine can be safely operated down to 2 gallons on the dipstick.</p><p>Never commence operations at this minimum level.</p><p>Oil changes are recommended at 100 hour intervals, or more often if conditions require it.</p><p>Clean cooler (pressure wash) as required or on annual inspections.</p><p>TIRE INFLATION</p><p>The main tires are inflated to a pressure of 41 psi (unloaded) or 43 psi (loaded). The tail</p><p>wheel tire is inflated to a pressure of 50 psi (loaded or unloaded).</p><p>LIFTING AND JACKING</p><p>A jack pad is provided with each aircraft for the main gear . To install the jack pad, lay a soft</p><p>rag on the inside so that it will not chip the paint from the main gear leg and slide the jack pad up</p><p>the lower end of the main gear leg until it is snug. It will be necessary to remove and replace the</p><p>lower Ty-rap that holds the brake line in place. The Ty-rap is a T150M-0 (Tyton) and should be</p><p>stocked as a standard spares item. After the jack pad is in place, install the bolt and nut through</p><p>the pad flanges with the bolt on the top side of the gear leg. This is to keep the pad from spreading</p><p>apart and slipping. Use a small hydraulic jack to lift the wheel off the ground. Be sure the tail</p><p>wheel is locked, and chocks are in place on the other main wheel. The hopper should be empty</p><p>before jacking.</p><p>CAUTION: Care should always be taken when the aircraft</p><p>is lifted to prevent damage to the aircraft or harm to people near it.</p><p>To jack the tail wheel, place a small board (a short 2 x 4) under the tail spring about mid-</p><p>way between the forward spring attach bolt and the main clamp block that attaches the spring to</p><p>the fuselage. Place the jack on the board and lift the wheel. Be sure the parking brake is set before</p><p>jacking.</p><p>If the tail spring is to be removed or checked for looseness, or have bolts changed, place the</p><p>small hydraulic jack under the point of the L/H stabilizer strut attach fitting that welds to the</p><p>lower fuselage longeron. Again, be sure the parking brake is set before jacking.</p><p>If the main gear springs are to be checked for looseness, or bolts changed (other than the</p><p>clamp bolts), the aircraft must be lifted with a hoist, as there are no jack points on the wing due</p><p>to the large deflections of the main gear springs. A sling should be constructed with each side of</p><p>the sling equipped with a strong hook that will be installed in the lifting eyes on the engine</p><p>crankcase. Be sure to have a spreader bar installed in the sling that will keep the cables from</p><p>chafing the cylinders, and to assure that the cables are pulling in the line of the lifting eyes on the</p><p>crankcase. It will be necessary to remove the prop cable support from the L/H lifting eye before</p><p>hoisting the aircraft. There are surplus slings available that can be modified slightly to fit the</p><p>R1340 by shortening the spreader bar. These slings can be supplied by the factory if desired.</p><p>It is also permissible to hoist the aircraft from the engine crankshaft behind the prop hub.</p><p>Be sure to have the hopper empty before hoisting. A two-ton hoist should be used, and as</p><p>the wheels clear the ground, place an empty 55 gallon drum with sufficient boards under each</p><p>wing at the tie-down locations to steady the aircraft and provide safety in case the hoist should</p><p>fail. Do not attempt to jack the wings at the tie-down rings.</p><p>MAIN WHEELS</p><p>To remove a main wheel, jack the wheel clear of the ground per previous instructions. With</p><p>a 7/16" wrench, remove the eight AN4 bolts attaching the two halves of the brake assembly.</p><p>Leave the brake line connected and slide the brake assembly out of the way. Next remove the</p><p>snap ring on the inboard side of the wheel that holds the felt grease retainer in place. This</p><p>facilitates wheel removal and re-installation. Then remove the outer snap ring and dust cap,</p><p>remove the two cotters in the castellated nut, and back off the castellated nut. The wheel can</p><p>then be pulled free of the axle.</p><p>If the tire is to be removed, deflate and then remove the two wheel halves. To mount a new</p><p>tire and tube position the tube in the tire so that the balance band on the tube is aligned with</p><p>balance mark on the tire. The inside of the tire and the outside of the tube should be lightly</p><p>dusted with talc before installation. If no balance band is found on the tube align the valve stem</p><p>with the balance mark on the tire. When re-mounting the tire and tube, apply enough air</p><p>pressure in the tube to allow the tube to take shape and position itself properly in the tire before</p><p>the two rim halves are assembled.This will help prevent pinching the tube between the rim</p><p>halves. Torque wheel bolts 100 inch-pounds at the nut. Inflate to 41 psi. Clean bearings and</p><p>hand pack with Mil-G-7711 general purpose grease. Before the wheel is re-installed, inspect the</p><p>cast aluminum torque plate for cracks and check the four axle attach bolts for proper torque (550</p><p>inch-pounds at the nut). Wipe axle clean and slide inner grease seal and bearing on axle. Position</p><p>wheel and tighten castellated axle nut until a slight bearing drag is felt as wheel is turned. Back</p><p>off nut to nearest castellation and install two MS24665-351 cotters. Position inner grease seal</p><p>and install snap ring. Install outer dust cap and snap ring and rotate wheel to check for possible</p><p>drag of cotter head on dust cap. The cotter head should protrude no more than 1/8" above the</p><p>flat for dust cap clearance. Check brake linings for wear and re-install on torque plate. The eight</p><p>AN4 bolts in the wheel cylinders require 120 inch-pounds torque.</p><p>MAIN WHEEL ALIGNMENT</p><p>1. Difference in forming of the main gear legs requires the use of tapered shims to provide</p><p>the correct camber and toe-in on the main wheels.</p><p>2. The aircraft is to be fueled, but with empty hopper.</p><p>Taxi aircraft a short distance in a straight line to allow the gear legs to assume the natural</p><p>position. The aircraft should be on paved surface or flat smooth ground.</p><p>3. A long straight edge is placed across the front of the tires approximately at axle height.</p><p>This straight edge is supported by blocks, or cans, or both. A 24" or larger carpenter’s</p><p>Maintenance Page 2 Air Tractor, Inc.</p><p>May 2, 1994 AT-401</p><p>square is placed against the straight edge and the outside surface of the tire, and held</p><p>level with the ground and at axle height. The tire should be square with the straight edge,</p><p>or have up to 1/8" toe-in, measured at the most outboard part of the tire.</p><p>4. Camber is then measured by placing a protractor on the vertical axis of the wheel through</p><p>the axle. Camber should measure 5o+/- 1o.</p><p>5. Should the wheel fail to check within these limits, the axle bolts are removed and the</p><p>tapered shims rotated, deleted, or added to until the wheels check with these limits.</p><p>6. The use of shims is limited to no more than 4o of change in the axle centerline from a line</p><p>perpendicular to the face of the landing gear leg in the center of the bolt pattern. Beyond</p><p>4o, bolts through the torque plate will cause a preload in the torque plate due to the</p><p>interference fit that could cause cracking. To determine if more than 4o exists, measure</p><p>the thickest and the thinnest part of the shim (or shims) used. Subtract the thinnest</p><p>measurement from the thickest. If this amount is equal to or less than .227", there is no</p><p>more than 4o of change in the axle centerline. If more than .227" exists, consult the</p><p>engineering department immediately.</p><p>7. If shims are removed, or bolts changed, be sure the steel round plate is positioned with</p><p>the countersunk side of the holes under the bolt heads.</p><p>BRAKES</p><p>The wheel brake units are Cleveland 30-18400 L/H and 30-18450 R/H. The brake unit</p><p>consists of the wheel cylinder assembly and the torque plate, which is attached to the gear leg</p><p>with the four axle bolts. The torque plates are not interchangeable from right to left, but the</p><p>cylinder assembly can be converted to a R/H or a L/H by moving the bleed screw to the fluid</p><p>entry port.</p><p>Brake fluid used is red Mil-H-5606A petroleum-base fluid which is used in most light</p><p>aircraft. Do not use automotive brake fluid as this will swell the O-rings.</p><p>The wheel units can be removed by using a 7/16" wrench to remove the eight AN4 bolts</p><p>attaching the two halves of the brake assembly. The brake line may be left connected if only the</p><p>linings are to be changed. Linings are Cleveland p/n 66-59 and are attached with Cleveland p/n</p><p>105-2 rivets. There are 16 linings and 32 rivets per aircraft.</p><p>Each brake assembly has four pistons which are Cleveland p/n 92-29 and have an O-ring</p><p>installed which is a Cleveland p/n 101-232. Each piston also incorporates a drag ring which</p><p>holds the piston against the backing plate of the lining so that excessive pedal travel is not</p><p>required for positive brake action.</p><p>To remove the pistons in order to change O-rings, remove the brake line and apply hydrau-</p><p>lic pressure at the fluid entry port. The pistons are aluminum and should be checked for wear, or</p><p>burrs that could cut the O-ring. Check the bore in the housing at the same time. When installing</p><p>new O-rings, soak them in brake fluid before placing them on the pistons. Re-install the pistons</p><p>with care, so that the O-ring is not damaged.</p><p>The brake disc is a Cleveland p/n 164-05600 and is attached to the bolts that attach the</p><p>two rim halves together. The wheel must be removed from the aircraft per previous instructions,</p><p>the tire deflated, and the wheel disassembled in order to remove the brake disc. With the new</p><p>brake disc in place, re-assemble wheel and tire per previous instructions.</p><p>Air Tractor, Inc. Maintenance Page 3</p><p>AT-401 May 2, 1994</p><p>BRAKE MASTER CYLINDERS</p><p>The master cylinders are Cleveland p/n 10-23F. The upper end is bolted to an aluminum</p><p>strap connected to the rudder pedal. Both the strap and the pedal have bronze bushings that can</p><p>be replaced when worn. The bushings are oil-impregnated and do not require lubrication.</p><p>The lower end of the master cylinder has a clevis attached with an AN316-5 check nut. If</p><p>the rudder pedal position (angle) should need changing for pilot comfort, the check nut can be</p><p>loosened, and the round plunger immediately below can be rotated with finger pressure in either</p><p>direction to increase or decrease the angle that the brake pedal makes with the cockpit floor.</p><p>When desired angle is obtained, snug check nut.</p><p>To remove the master cylinder, loosen check nut and rotate plunger out of the clevis. Then</p><p>remove the bolt attaching the master cylinder to the aluminum strap and disconnect the two</p><p>brake lines at the cylinder.</p><p>A repair kit is available for the master cylinder which is Cleveland p/n 199-09100. The</p><p>cylinder may be dis-assembled and repair parts installed per instructions furnished with the kit.</p><p>If the check nut at the top is left in the original position, the pedal angle will be the same as</p><p>before when the master cylinder is re-installed. Be sure the clevis is free to swing with the master</p><p>cylinder through the full range of rudder pedal travel. If it does not, the two plates which attach</p><p>the clevis are too close together and require an additional spacer washer.</p><p>If a spot of brake fluid appears on the cockpit floor on the L/H side it does not necessarily</p><p>mean that the master cylinder is leaking. The usual cause is over-filling the brake reservoir, so</p><p>that when brakes are used, and fluid returns to the reservoir, it sometimes leaks through the</p><p>vent hole in the reservoir cap.</p><p>BRAKE BLEEDING</p><p>If air enters the brake system because of worn O-rings or the replacement of brake system</p><p>components, the brake pedal will become “soft” and the brakes lose their effectiveness. It will then</p><p>be necessary to bleed the brakes to remove the air.</p><p>The conventional practice of placing a pressure pot line at the bleed screw location on the</p><p>wheel cylinder and forcing fluid up through the system generally does not work. The factory</p><p>practice is to place one person in the cockpit and another at the wheel cylinder with a bleed screw</p><p>wrench and a Coke bottle to catch the fluid. Before the bleeding process begins, it is necessary to</p><p>obtain a short piece (about 6"long) of windshield wiper hose which will fit snugly over the bleed</p><p>screw head so that all fluid can be caught in the Coke bottle and not wasted.</p><p>The procedure is as follows:</p><p>1. The cockpit man pulls on the parking brake and leaves it on. Then he pumps the pedal on</p><p>the side being bled several times until the pedal begins to get firm. The parking brake is</p><p>left on since it is actually a one-way check valve.</p><p>2. Then the cockpit man pushes the pedal and shouts “Open” to the man at the wheel</p><p>cylinder who proceeds to open the bleed screw with a 1/4" open-end wrench. Brake fluid</p><p>and air then rush through the bleed screw, through the hose , and into the Coke bottle.</p><p>3. The cockpit man, who has held the pedal all the way down, then shouts “Close” as soon as</p><p>the pedal reaches the down position, and the other person closes the bleed screw immedi-</p><p>ately.</p><p>Maintenance Page 4 Air Tractor, Inc.</p><p>April 1, 1998 AT-401</p><p>4. The cockpit man uses the procedure outlined in (1) to obtain a firm pedal and again</p><p>repeats step (2) and (3).</p><p>5. The above procedure is repeated as many as a dozen or so times until a firm brake is</p><p>obtained with the parking brake off. Be sure to add brake fluid to the reservoir before the</p><p>reservoir is emptied or else you will have to start all over again. Don’t use the fluid in the</p><p>Coke bottle as it will have bubbles of air. When the bubbles are gone it is OK to use, if the</p><p>fluid is clean.</p><p>6. Repeat the process for the other wheel.</p><p>PARKING BRAKE</p><p>The parking brake valve used on later Air Tractors is a Scott p/n 4500A-2. Two of these</p><p>valves are mounted together with a common lever to pull the valve to the “ON” position. O-Rings</p><p>within the valves may be replaced when needed.</p><p>TAIL WHEEL</p><p>The tail wheel is a Cleveland p/n 40-168. Keeping the bearings properly lubricated is the</p><p>key to long bearing life. A grease fitting is installed in the side of the wheel.</p><p>To remove the tail wheel, jack the wheel clear of the ground per previous instructions and</p><p>remove the long AN6C63A bolt that attaches the axle to the fork. Note the method of safety wire</p><p>on the large stainless jam nut and cut the wire loose from the fork. The tail wheel is now free and</p><p>ready for dis-assembly. Back off the jam nut from the axle and remove the axle. Inspect the axle</p><p>for wear at the bearing positions, as insufficient greasing procedures will cause the bearing to</p><p>turn on the axle and ruin both parts. Inspect the AN6 bolt for wear and straightness, and slide</p><p>the bolt through the fork to check the hole in the fork for wear. There should be no wear in the</p><p>fork holes since there is no movement between fork and bolt. If the tire is to be removed, deflate</p><p>and remove the bolts holding the wheel halves together. Since the rim halves were sealed the</p><p>sealer may hold the parts together and tapping the rims with a wooden block may be necessary to</p><p>split the wheel. Don’t forget to remove the valve stem nut and push the stem until it is loose from</p><p>the wheel half.</p><p>Clean all parts and re-assemble wheel and tire as described in the Main Wheel section on</p><p>page 2.</p><p>Tail wheel bearings are Timken L44643LA cone (the part with the rollers) and L44610 cup</p><p>(the part pressed into the wheel half.) Hand pack the bearings with Mil-G-7711 grease, and install</p><p>wheel on the axle. Install the 40034-1 jam nut and 40051-1 tongue washer on the axle with the</p><p>round shoulder inboard and tighten until all bearing slack is removed but the wheel is free to</p><p>turn. Inflate the tire to 50 psi. Grease the AN6C63A axle bolt and install wheel and axle assembly</p><p>on the fork. Torque the nut to 160 inch-pounds. Safety the jam nut against the rotation of the</p><p>wheel with MS20995C32 stainless safety wire.</p><p>Air Tractor, Inc. Maintenance Page 5</p><p>AT-401 April 1, 1998</p><p>TAIL WHEEL FORK</p><p>The tail wheel fork may be removed from the housing by removing the single AN4C26A</p><p>stainless bolt from the arm assembly that connects to the centering springs. With the fork</p><p>removed, check for wear on the spindle at the bronze bearing locations. Also check for condtion of</p><p>the steel bushing that the lock pins drop into. This bushing is pressed into the steel plate at the</p><p>bottom end of the spindle and staked in four places on each side of the plate with a center punch.</p><p>This holds the bushing in place since it has a beveled edge on both sides. The bushing is p/n</p><p>40042-1. Excess wear on the fork spindle at the bronze bearing locations are indication that</p><p>grease is not reaching the proper area. To grease the bronze bearings properly, jack the tail wheel</p><p>clear of the ground and apply grease at the fitting on the housing, and rotate the fork until grease</p><p>is running out of the full perimeter of both upper and lower bronze bushings. Excessive wear in</p><p>the spindle will require a new fork assembly which is p/n 40040-9 and includes the steel lock pin</p><p>bushing. The centering springs are p/n 40044-1 and attach to a p/n 40035-1 bracket which</p><p>wears on a p/n 40036-1 bushing. The bolt is a AN4C7A.</p><p>TAIL WHEEL FORK HOUSING</p><p>The housing is attached to the tail spring with two AN10-H14A bolts, and MS20995C32</p><p>safety wire ties the bolts heads together. These bolts have a tendency to loosen in service,</p><p>particularly in the first 100 hours of operation as paint between mating surfaces is compressed.</p><p>At 100 hour intervals, the tail wheel should be jacked clear of the ground, and with the locking</p><p>pin in place give the tail wheel a vigorous tug from side to side to check for movement between</p><p>the housing and the spring. Torque the bolts to 1,700 inch-pounds. For row-crop operation from</p><p>smooth strips these bolts should be replaced at least every 1,600 hours and for rice operation</p><p>from rough strips they should be changed every 800 hours or once a year. Be sure to grease the</p><p>bolts before installation with G.P. Grease, and an added precaution would be to apply grease to</p><p>the threads of the housing to prevent the bolt from seizing.</p><p>A brass wear plate is attached at the lower plate of the fork housing assembly. This plate is</p><p>attached with counter-sunk machine screws and if worn to the point where the machine screw</p><p>heads are flush, it should be changed. The brass plate is p/n 40018-2. The large bronze bushings</p><p>inside the housing are p/n 40023-1 (lower) and p/n 40024-1 (upper). These bushings are pressed</p><p>into place and may be driven out with a pin punch. The lower bushing has a chamfered end</p><p>which is positioned on the lower extreme of the housing at the brass wear plate. The housing</p><p>assembly is p/n 40017-1 which is less bushings, wear plate and attaching hardware and grease</p><p>fitting.</p><p>Maintenance Page 6 Air Tractor, Inc.</p><p>May 2, 1994 AT-401</p><p>TAIL WHEEL LOCK PIN AND HOUSING</p><p>The lock pin housing is p/n 40025-1 and attaches to the steel plate on the lower end of the</p><p>fork housing with four countersunk screws. The four holes in the base of the lock pin housing are</p><p>oversize to allow adjustment of the locking pin. If the aircraft tends to steer to the left or to the</p><p>right on the ground with the lock pin engaged, it is necessary to re-position the lock pin housing.</p><p>Jack the tail wheel clear of the ground, lift the lock pin up and swivel the fork to one side so that</p><p>the four screw heads are exposed. Make a pencil mark along the edge of the lock pin housing</p><p>plate for a reference and estimate the amount of movement for the lock pin housing. Loosen the 4</p><p>screws and move the housing the desired direction. Swivel the fork back into position and allow</p><p>the locking pin to engage the fork, then tighten the two outboard screws. Then rotate the fork</p><p>back so that the two inboard screws can be tightened. Check the lock pin again to see if it freely</p><p>engages the fork. Taxi the aircraft in a no-wind condition or if there is a light wind, taxi both up-</p><p>wind and down-wind with the rudder pedals in the neutral position and the stick back so that</p><p>you are sure the lock pin is engaged. Keep adjusting the locking pin housing until the aircraft will</p><p>taxi in a straight line.</p><p>During annual inspections (or more frequently if required) remove the housing and slide out</p><p>the locking pin to check it for wear and straightness. The compression spring inside the housing</p><p>should also be checked for broken coils. The locking pin is p/n 40021-1 and the spring is p/n</p><p>40026-1.</p><p>MAIN AND TAIL GEAR ATTACH BOLTS</p><p>The bolts attaching the main and tail gear springs to the fuselage structure are among the</p><p>most important structural components of the aircraft. Being structural components under con-</p><p>stant stress, these bolts have definite fatigue lives. The predictability of the fatigue life of each bolt</p><p>is impossible due to the wide variety of operating conditions that include smoothness of launch-</p><p>ing strips, number of landings per hour, pilot landing technique, load carried, the way the turns</p><p>on the ground are made, the way the brakes are used, and many other small but significant</p><p>factors. Dropping in over the trees and hitting</p><p>the ground during a spray run may not cause a</p><p>gear bolt failure, but the effect on the fatigue life of the bolt could be the same as several</p><p>thousand landings on a rough strip. A bolt that is not tightened to the proper torque, especially</p><p>when there is visible clearance between the gear spring and the fuselage, will last only a fraction</p><p>of the time normally expected.</p><p>We have seen paved-landing strips that had big potholes impossible to miss when landing,</p><p>that must impose huge loads on the forward main gear clamp bolts. How many times do you hit</p><p>the potholes before the bolts break? Some strips are so rough you wouldn’t dare drive your empty</p><p>pickup over 30 mph down the strip, yet there goes an Air Tractor with a ton of fertilizer bouncing</p><p>along at 80 mph on a still day just before lift-off. Lie down on the ground and look at the massive</p><p>structure supporting all four wheels of your pickup. Now look at your Air Tractor gear support,</p><p>and consider the leverage that exists between the gear leg length, and the distance between the</p><p>clamp block bolts.</p><p>What we are trying to tell you is that your aircraft is not a tank, the gear will support a</p><p>surprising amount of load, the bolts will take a lot of tough licks, but don’t press your luck and</p><p>think that they will last forever without breaking.</p><p>Air Tractor, Inc. Maintenance Page 7</p><p>AT-401 September 15, 1989</p><p>Accordingly, we have established what we feel is a conservative, yet realistic time period for</p><p>gear bolt changes, based on field experience at this time. The bolt life shown is based on normal</p><p>operations, and if you are the one with the potholes or super-rough strips, cut the time between</p><p>bolt changes in half. If your aircraft hits the ground or a ditch bank during spraying, change the</p><p>forward clamp bolts immediately. If you discover slack in the large 1.0" bolt attaching the main</p><p>gear leg, change it immediately. Bolts are cheap.</p><p>Hours shown are for normal operations in row-crop or rice operations. If your business</p><p>combines both types of flying, use an average of the two figures. If your strips are rougher than</p><p>normal cut the hours shown in half. If you hit an obstruction with the main gear, change the</p><p>forward clamp bolt immediately and check the clamp block for straightness.</p><p>Bolt Location Bolt Size Bolt Life Bolt Life Wrench On ( )</p><p>(On Fuselage) ________ (Row-Crop Op.) (Rice Op.) Torque</p><p>Fwd main gear NAS152DH43 1,000 hours 500 hours 250 ft. - lbs (head)</p><p>Clamp block</p><p>Aft main gear NAS152DH43 2,000 hours 1,000 hours 250 ft. - lbs. (head)</p><p>Clamp block</p><p>Inbd main gear NAS156A86 2,000 hours 1,000 hours 500 ft. - lbs. (nut)</p><p>Large bolt</p><p>Tail Spring AN7-31A 1,000 hours 500 hours 45 ft. - lbs. (nut)</p><p>Clamp bolts</p><p>Tail Spring AN6-17A 600 hours 300 hours Snug only</p><p>Forward bolt</p><p>2 bolts aft end AN10H14A 2,000 hours 1,000 hours 142 ft. - lbs. (head)</p><p>Tail spring</p><p>TAIL GEAR SPRING</p><p>The tail gear spring is p/n 40060-1. It is machined of E-4340 aircraft quality steel, formed,</p><p>heat-treated, and shot-peened for fatigue resistance. It is sand blasted and primed with Alumigrip</p><p>30-Y-94 primer and finished with Alumigrip G-9046 yellow polyurethane paint.</p><p>The forward attachment of the spring to the fuselage frame is with an AN6-17A bolt. It is</p><p>clamped at the rear attachment with p/n 40149-1 clamp block which attaches to the fuselage</p><p>frame with two AN7-31A bolts. There is a p/n 40146-2 aluminum pad that is installed between</p><p>the clamp block and the spring to allow the spring to work without putting secondary loads into</p><p>the fuselage frame or attach bolts. There are square .020 thick stainless shims (p/n 40065-1) and</p><p>sometimes a spacer washer located between the clamp block and the fuselage frame. During</p><p>annual inspections the tail gear should be jacked at the stabilizer strut fitting as described under</p><p>Maintenance Page 8 Air Tractor, Inc.</p><p>April 1, 1998 AT-401</p><p>“Lifting and Jacking” and the tail spring checked for looseness at the clamp block. Looseness can</p><p>be eliminated by removing one or more of the square stainless shims from under the clamp block.</p><p>With the clamp block removed, also check the aluminum pad for condition.</p><p>The forward spring attach bolt AN6-17A. should be changed every 600 hours or once a year</p><p>for row-crop work and every 300 hours if working from rough strips in rice operations. Besides</p><p>saving a possible fatigue failure, the forward bolt tends to freeze up if not changed often. Be sure</p><p>to grease the bolt and snug the nut only (no torque) as the spring must move on the bolt.</p><p>The clamp bolts should be changed every 1,000 hours for row-crop work and every 500</p><p>hours if operating from rough strips in rice operations. Torque the clamp bolts to 600 inch-</p><p>pounds (torque wrench on bolt head), and make sure there are sufficient shims between the</p><p>clamp block and the fuselage frame to prevent bending the clamp block as the bolts are torqued.</p><p>The tail gear spring will fatigue and break at some point in the life of the aircraft. The</p><p>number of hours before failure will vary considerably as some operators make many more</p><p>landings per flight hour than others, or carry heavier loads, or operate from very rough strips.</p><p>Pilot technique is a factor also, since some pilots are very rough on airplanes. For these reasons</p><p>it is not possible to predict when a failure might occur.</p><p>Usually the tail spring will show signs of yielding just prior to failure and the tail of the</p><p>aircraft will sit a slight bit lower to the ground than previously. Sometimes during the first 100</p><p>hours or so of operation a measurement should be taken and recorded from the clampblock to</p><p>the ground or hangar floor. The aircraft should be fully fueled, and with a full hopper. At various</p><p>intervals this measurement should be checked, and after 1,000 hours check the measurement at</p><p>least every 50 hours. Although service history for the Air Tractor is relatively limited, it appears</p><p>that the tail spring should be changed about every 1500 hours for worst conditions of rice</p><p>operations from rough strips, and every 2,000 hours for the best conditions of row-crop work</p><p>from smooth strips. Each operator should determine at what point in between these extremes his</p><p>operation fits and change the tail spring at the appropriate interval, unless the measuring process</p><p>described earlier indicates yielding. In that case the spring should be changed immediately. When</p><p>ordering a new tail gear spring, also order two each 40065-1 shims in case they are needed.</p><p>For everyone’s protection, take a cutting torch and destroy the old spring when it is re-</p><p>placed.</p><p>MAIN GEAR SPRING</p><p>The main gear spring is p/n 40007-3 and will fit on either side of the aircraft. It is machined</p><p>of E-4340 aircraft quality steel, formed, heat-treated, and shot-peened for fatigue resistance. It is</p><p>sandblasted and primed with Alumigrip 30-Y-94 primer and finished with Alumigrip G-9046</p><p>yellow polyurethane paint.</p><p>The inboard attachment of the spring to the fuselage frame is with a NAS156A86 bolt,</p><p>MS20002C16 washer under the bolt head (be sure the chamfered side of the washer is next to the</p><p>head), one or more MS20002-16 washers under the nut, AN310-16 nut, and MS24665-360</p><p>cotter. The bolt is installed upside down and torque should be 6,400 inch pounds (torque wrench</p><p>on bolt head). A simple adapter for your torque wrench is a short piece of 1.0" hex stock to enter</p><p>the bolt head, and a 1.0" socket for your torque wrech.</p><p>The inboard bolt should be changed every 2,000 hours for row-crop and every 1,000 hours</p><p>for rice operations. It is necessary to hoist the aircraft as described under “Lifting and Hoisting”</p><p>Air Tractor, Inc. Maintenance Page 9</p><p>AT-401 April 1, 1998</p><p>when changing the inboard bolt. Be sure to grease the bolt with general purpose grease before</p><p>installing. Also, be sure the bolt is marked “R” on the head to indicate the threads were rolled</p><p>after heat-treat.</p><p>The gear spring is clamped to the fuselage frame with a p/n 40148-1 clamp block with two</p><p>NAS152DH43 bolts, MS20002C12 washers under the bolt head (make sure the chamfered side of</p><p>the washer is</p><p>under the bolt head) and various numbers of McMaster p/n 3088A324 round shim</p><p>washers between the clamp block and the fuselage frame. The shims are selected to allow the</p><p>bolts to be fully torqued without bending the clamp block. The McMaster p/n 3088A324 shims</p><p>are .010 thick. If too many thick shims are used the gear connection will be too loose and will</p><p>rattle during taxi or landing. If the gear leg becomes loose during service even though the clamp</p><p>block bolts are at full torque it is necessary to remove a shim.</p><p>The method empoyed at the factory to determine the amount of shims required is to install</p><p>the clamp block and fully torque the bolts before installing the large inboard bolt. The block is</p><p>checked for straightness with a small straight edge (a six-inch steel scale is OK) to be sure the</p><p>block is not bent by not having sufficient shims. Then the gear leg is grasped at the lower end,</p><p>given an outboard tug by hand. A moderate tug should move the inboard end of the leg down</p><p>from the attach bushing in the fuselage frame a distance of 1/8" to 1/4". If it is a greater distance</p><p>than 1/4" the connection is too loose, and a thinner shim is tried and the process repeated. Once</p><p>the proper shims are determined, the bolts are loosened and the large inboard bolt is installed.</p><p>Then the clamp bock bolts are tightened to full torque (3,000 inch-pounds) and MS20995C32</p><p>wire is used to safety the two bolt heads together.</p><p>An adapter for your torque wrench may be made from a short piece of 5/8" hex stock to</p><p>enter the bolt head, and a 5/8" socket for the torque wrench. Be sure to grease the bolts before</p><p>installing. The clamp block bolts should also have the letter “R” stamped on the head to indicate</p><p>the threads were rolled after heat treat.</p><p>For row-crop operations the forward clamp bolt should be changed every 1,000 hours and</p><p>the aft clamp bolt every 2,000 hours. For rice operations from rough strips the forward bolts</p><p>should be changed every 500 hours and the aft bolt every 1,000 hours.</p><p>If an obstruction is hit with the main gear, change the forward clamp bolt immediately and</p><p>check the clamp block for straightness. The forward clamp bolt can be changed without hoisting</p><p>the aircraft. The parking brake should be set, and use care so as not to disturb the shims that</p><p>are in place.</p><p>Since each main gear leg is slightly different in thickness, and since each clamp block is</p><p>machined within a specific tolerance, it is necessary to make a shim selection as described earlier</p><p>if either the gear leg or the clamp block is changed.</p><p>As in the case of the tail gear spring, the main gear spring will fatigue and break at some</p><p>point in the life of the aircraft. Again, the number of hours before failure will vary considerably as</p><p>some operators make more landings per hour than others, or carry heavier loads, or operate from</p><p>very rough strips. Pilot technique is again a factor, as some pilots are very rough on airplanes.</p><p>For these reasons it is impossible to predict when a failure might occur.</p><p>Service history is still relatively limited but in the interest of safety and the high financial</p><p>consequences of a broken main gear leg, it would be advisable to take a highly conservative</p><p>approach and change the main gear springs well before the probable fatigue life. The main gear</p><p>springs should be changed in accordance with Service Letter #104.</p><p>Maintenance Page 10 Air Tractor, Inc.</p><p>April 1, 1998 AT-401</p><p>When the main gear springs are changed, use new bolts and nuts at all locations. The axle</p><p>attach bolts are NAS147-53. Install the springs to the fuselage in accordance with the instruc-</p><p>tions in this section and install the axles to the spring using the procedure to check camber and</p><p>toe-in outlined in the section “Main Wheel Alignment”. Be sure to make log book entries when</p><p>bolts or gear springs are changed.</p><p>Whenever the airplane is ground-looped or involved in an incident that puts a permanent</p><p>bend in one gear spring, the other spring must be changed as it may have been overstressed.</p><p>When ordering new main gear springs or clamp blocks also order 10 ea. McMaster p/n</p><p>3088A324 shims in case they are needed. In addition, the large aluminum tapered shims at the</p><p>axle attachment might need an addition or change so it would be a good idea to order 2 ea 40011-</p><p>2 shims and 2 ea 40011-3 shims in case they are needed.</p><p>WINGS</p><p>The wing is of all-metal construction with the main spar designed to take all of the bending</p><p>load. Thick wing skins are employed near the wing root with a gradual drop in thickness at each</p><p>skin lap as wing loads diminish. No span-wise stringers are used in order to simplify construction</p><p>and repairs and for that reason wrinkles in the upper skin and "cans" between the ribs will be</p><p>noticed during maneuvers with heavy loads. This is a natural condition and unless the cans or</p><p>wrinkles change noticeably in a particular location there is no cause for alarm. Any changes as</p><p>mentioned will require close inspection of all internal structural parts in the area where the</p><p>change has taken place.</p><p>The wing leading edge is of .040 thick 2024-T3 and can be replaced in the field as described</p><p>under the Repairs section of this manual. The wing rear spar attach plate is of 1/4" thick heat</p><p>treated 4130N steel for extra strength and resistance to corrosion during fertilizer applications. It</p><p>is cadmium plated and painted with Air Ag yellow epoxy before assembly to the rear spar.</p><p>All wing parts are scrubbed with an etching solution, and dipped into an Alodine 1200</p><p>solution, then primed before assembly. Skin laps on the top side of the wing are sealed with TBM</p><p>PKMMC236A1/2 as in the wing root to prevent chemical entry.</p><p>WING ATTACHMENT TO FUSELAGE</p><p>Two wing attach angles are used to attach the wing main spar to the fuselage vertical tube</p><p>just aft of the main spar. There are three AN5-25A bolts that attach each vertical tube to the wing</p><p>angles.</p><p>It should also be noted that there is no bolt through the attach angle and through the small</p><p>leg of the lower spar cap. This is to eliminate bolt fretting and make the joint more fatigue</p><p>resistant. Torque bolts to 200 inch-pounds at the nut.</p><p>The wing attach angles are p/n 20692-1 and are attached to the main spar with three AN5-</p><p>12A and one AN5-13A bolts. If it is necessary to change the wing attach angles due to bolt wear</p><p>or fuselage repairs, ask the factory for detailed instructions on how to drill the attach angles at</p><p>the time they are ordered, as these angles are drilled to match each individual aircraft.</p><p>The rear spar plate is attached to the fuselage frame with a single NAS1307-21 bolt. These</p><p>bolts wear slightly and should be checked at 1,000 hour intervals, and replaced if worn or rusty.</p><p>Do not use AN bolts at this location. To remove the bolts, first remove the lower wing gap cover</p><p>Air Tractor, Inc. Maintenance Page 11</p><p>AT-401 March 30, 2003</p><p>Maintenance Page 12 Air Tractor, Inc.</p><p>September 16, 2009 AT-401</p><p>which is attached with screws. Place a small hydraulic jack under the wing rear spar plate</p><p>and apply only a small amount of pressure to support the wing when the bolt is removed. Lock</p><p>the parking brake so the aircraft will not move. Remove the nut and drive the bolt out with a small</p><p>hammer gently, protecting the threads from damage. Inspect the bolt visually, then place it on a</p><p>smooth plate and rotate to see if it is bent. Inspect for thread damage or rust. Do not use</p><p>excessive force to remove the bolts, and do not heat. If there is difficulty in removing the bolts,</p><p>contact the factory.</p><p>We encourage replacement of old bolts with new bolts at all times, but if the old bolts are in</p><p>good shape and the time intervals mentioned above are not exceeded, they may be re-installed. Be</p><p>sure to grease the bolts before installing. Torque values are 300 inch-pounds (Torque wrench on</p><p>nut).</p><p>WING CENTER SPLICE CONNECTION</p><p>The main spar caps of each wing are attached to each other with p/n 20591-1/-2 aluminum</p><p>attach blocks (upper) and p/n 21087-1/-2 steel attach blocks</p><p>(lower). It takes one of each block</p><p>per spar cap. The main spar webs are attached to each other by the p/n 20990-2 plate of 1/2"</p><p>thick 4130N steel. The connection to the fuselage on the aircraft center-line is made with a p/n</p><p>20178-1 steel plate of .063 4130N connected to the fuselage structure with two AN5-23A bolts,</p><p>and to the two 3/4" bolts through the 20591-1 upper spar cap attach block.</p><p>There are four p/n 20177-1 tube-nut welded assemblies and two p/n 20367-1 sleeves in</p><p>each wing installation. The sleeves and tube-nuts are drilled 9/32" and reamed .3125 after the</p><p>tube-nuts have been fully tightened, and two AN5-16A bolts installed in each sleeve. If the wings</p><p>are removed from the aircraft, it is usually necessary to replace the four tube-nut assemblies and</p><p>the two sleeves since the .3125 reamed holes through both parts will probably not line up. In this</p><p>case, tighten the new tube-nuts 1920 inch pounds torque, position the new sleeves mid-way</p><p>between the tube-nuts, drill 9/32" through the sleeve and tube-nut, and ream .3125 for the</p><p>AN5-16A bolt installation.</p><p>The tube-nut and sleeve installation is to take the “Kick load” due to dihedral angle and</p><p>cancel it out by transferring this load from the upper spar caps to the lower spar caps.</p><p>To remove the wings, or to inspect the wing center splice connection properly, the hopper</p><p>should be removed. Torque values should be checked on the nuts (300 inch-pounds on the 3/8"</p><p>nut, 800 inch-pounds on the 1/2" nut, 550 inch-pounds on the 7/16" nut, 1,700 inch-pounds on</p><p>the 5/8" nut, and 1,920 inch-pounds on the 3/4" tube-nut assembly. There are NAS1306 bolts</p><p>through the small leg of each spar cap that attach to the 20990-2 plate on the aft side of the web.</p><p>These 3/8" nuts are checked for torque (300 inch—pounds). The NAS1306 bolts through the web</p><p>and the 20992-2 plate have a torque of 300 inch-pounds applied to the nut. The NAS1304 bolts</p><p>have a torque of 100 inch-pounds applied to the nut.</p><p>Inspect the entire splice connection carefully for signs of bolt working, corrosion, or cracks.</p><p>The critical area for the lower spar cap is a station 6.4" from the aircraft center-line where the</p><p>3/8" NAS bolt attaches the 21087-1 and -2 blocks to the main leg of the cap. The next critical</p><p>area of the lower spar cap would be in the rivet pattern attaching the small leg to the web from</p><p>approximate stations 20.0" to 25.0" which is where the inboard fuel tank wall is located. It would</p><p>Air Tractor, Inc. Maintenance Page 13</p><p>AT-401 September 16, 2009</p><p>also be advisable to check carefully the lower side of the main leg in the area where the fuel tank</p><p>bottom ends.</p><p>For appropriate inspection intervals of the wing center splice connection, see the</p><p>“Inspection” section of this manual. If a new wing is to be installed, contact the factory for wing</p><p>installation instructions at the time the wing is ordered.</p><p>WING WALK</p><p>The main wing walk is made of 3-M safety walk 12" wide and is p/n 20232-1. The small</p><p>round walk part is p/n 20234-1 and the flap walk is p/n 20233-1. Outboard of the main walk is</p><p>p/n 20565-1 walk.</p><p>The walk material has adhesive backing but in order to improve the bond to the wing skin,</p><p>3-M safety Walk Adhesive is applied to the wing surface. To prevent fuel from getting under the</p><p>walk and lifting it, 3-M Edge Sealing Compound is applied along the perimeter of the walk. If the</p><p>walk is changed, be sure to order the adhesive and the edge sealing compound for best results.</p><p>FUEL TANKS</p><p>The fuel tanks are sealed with PKMMC236A1/2 which is brushed on and PKMMC236B1/2</p><p>which is a thicker putty-like material for sealing corners or large cracks. Sealing between mating</p><p>parts is done during assembly, and final coating is done through the five inspection openings in</p><p>the top of the tank.</p><p>If a leak develops in service, remove the inspection plates on the lower side of the wing, and</p><p>with a flashlight and mirror determine which area of the tanks appear to be leaking. This is</p><p>diffcult and sometimes it is necessary to re-seal a large area of the tank to make sure the leak is</p><p>covered. Remove the fuel line from the tank to be drained and cap it off so that both tanks will not</p><p>need to be drained. Then drain the fuel into clean containers by removing the drain valve from the</p><p>tank flange. Then remove the inspection plate on top of the fuel tank nearest the leak area. There</p><p>are plate-nuts (NAS680-A4) riveted to the fuel tank top to facilitate plate removal.</p><p>Inspect inside of the fuel tank with a flashlight and mirror or a drop-light. CAUTION: Do not</p><p>turn either light off or on while the light is inside the fuel tank. A spark from the switch has</p><p>caused an explosion and injury in a past instance. Look for a void or bubble of air that could have</p><p>popped, leaving a pin-hole leak. If no suspicious areas are found, prepare to re-seal the general</p><p>area of the leak.</p><p>Clean the area to be re-sealed with an inhibited alkaline cleaner such as M.E.K. with a clean</p><p>white rag. A progressive cleaning procedure should be used. Wash one small area at a time, then</p><p>dry with a clean cloth before solvent evaporates to prevent redeposition of oil or fuel traces. To</p><p>maintain a clean solvent supply, always pour the solvent on the washing cloth.</p><p>The sealer kit consists of the proper portion of base compound and accelerator. The accelerator</p><p>contains some volatile materials which usually come to the surface so it is extremely important to</p><p>stir the accelerator thorougly in its container until an even consistency is obtained. Once the</p><p>accelerator is added to the base material the pot life is limited to two hours at 75oF, 50% relative</p><p>humidity. For every 10o F rise in temperature, application life is reduced by half, and for every</p><p>10oF drop it is doubled. High humidity at the time of mixing shortens application life. For this</p><p>reason, it is suggested that only 1/2 of the accelerator is mixed with 1/2 of the base material, so</p><p>that if the first attempt to seal the tank is unsuccessful, there will be one more mix of sealer</p><p>Maintenance Page 14 Air Tractor, Inc.</p><p>September 15, 1989 AT-401</p><p>left for another attempt before a new can has to be opened. If this approach is taken, be sure the</p><p>accelerator is sealed in an air-tight container as well as the base material, and that care is taken</p><p>to assure that exactly 1/2 of each component is mixed together.</p><p>Slowly stir the accelerator into the base compound and thoroughly mix approximately 7 to</p><p>10 minutes. Be sure to scrape the sides and bottom of the container in order to include all the</p><p>compound in the mixture and to assure uniform blending. Scrape mixing paddle periodically to</p><p>remove unmixed compound. Slow mixing by hand is recommended.</p><p>Obtain a small paint brush approximately 1/2" to 3/4" wide and trim the bristles to</p><p>approximately 1/2" long to increase brush stiffness. Brush the thoroughly mixed sealing</p><p>compound over the cleaned suspected leak areas in generous amounts but feather out any runs</p><p>that might occur. Watch for bubbles and re-seal any pin-holes. Inspect your work carefully, as</p><p>failure means doing the job all over again. Scrape off the old sealer from the fuel tank cover plate</p><p>and mating surface, being careful not to get any shavings inside the tank. Seal both the cover</p><p>plate and the mating surface and install cover plate. Where the sealer is squeezed out and around</p><p>the perimeter of the plate, use your finger to make a smooth fillet.</p><p>Allow the sealer to dry at least 6 hours (overnight is preferable) before fueling the tank.</p><p>Check carefully for leaks before connecting the fule line to the other tank. If the tank still leaks,</p><p>repeat the entire process until the leak is sealed.</p><p>FUEL TANK SENDERS</p><p>The L/H fuel tank sender has a shorter float arm than the R/H sender and is positioned</p><p>differently in the tank. For these reasons the cork at the end of the float arm is still about 3" from</p><p>the bottom of</p><p>the fuel tank when the L/H sender is at the end of its stroke and the receiver on the</p><p>instrument panel shows “E”. This results in about 3 to 4 gallons of fuel still remaining in the L/H</p><p>tank when the receiver shows “E”. The fuel tanks are inter-connected and if coordinated flight has</p><p>been maintained, the R/H tank will show about 1/8 full at the same moment the L/H tanks</p><p>shows empty.</p><p>The L/H tank sender is Rochester p/n C7740-87 and the R/H sender is p/n C7740-43. The</p><p>L/H sender is attached with five 1032 x 1 1/4 stainless screws, 20194-2 bushings and</p><p>AN363C1032 nuts. The R/H sender is attached with five 1032 x 1 3/4 stainless screws, 20194-1</p><p>bushings, and AN363C1032 nuts. Both sides have p/n 20173-1 teflon washers under the screw</p><p>heads for sealing purposes.</p><p>Both senders have a 60008-1 wire attached with a banana plug on one end which is</p><p>inserted into a banana jack mounted on the inboard fuel tank wall. If a sender is not working</p><p>properly, the procedure is to remove the inspection cover from the fuel tank top just forward of the</p><p>five sender attach screws and before removing the sender, first push the banana plug firmly into</p><p>the jack to be sure proper connection has previously been made. If this has no effect, pull out the</p><p>banana plug and connect to an Ohmmeter with the other lead ground. With the float arm all the</p><p>way down the Ohmmeter should read zero and with the arm all the way up the ohmmeter should</p><p>read 29-30 Ohms. Cycle the arm and the needle should not have an erratic movement. If all is OK,</p><p>the sender does not have to be replaced. If there is still indication of a faulty sender, remove the</p><p>five screws attaching it to the tank top, being careful not to damage the teflon washers under the</p><p>head of each screw. The fuel tank should be drained before the sender is replaced. The five</p><p>bushings</p><p>Air Tractor, Inc. Maintenance Page 15</p><p>AT-401 April 1, 1998</p><p>will probably be held in place by the tank sealing compound if care is ken when removing the</p><p>sender. Pull the banana plug from the jack and remove the sender.</p><p>If the R/H sender is being replaced the cork at the end of the float arm should just touch the</p><p>bottom of the tank when the arm is at the end of its stroke. It should touch the top of the tank at</p><p>the upper end of the stroke. If it will not quite touch the tank bottom or touches too soon, bend</p><p>the arm gently by hand to achieve the desired position. The L/H sender will not touch the tank</p><p>bottom, but will touch the tank top.</p><p>Before re-installing the inspection plate on the fuel tank top, move the float arm through the</p><p>full stroke with the battery switch “On” and the receiver switch on the proper tank to see that the</p><p>sender is working properly. Seal the inspection plate per instruction in “Fuel Tank” and re-install.</p><p>FUEL TANK RECEIVER</p><p>The fuel tank receiver is p/n 50698-1. There is an adjustment screw for the “E” side of the</p><p>needle range on the center lower side of the instrument face. The trimmer screw for the “F” side of</p><p>the needle range is mounted behind the upper panel to the right of the chip detector light, and</p><p>since the slotted end of the trimmer screw is toward the cockpit floor, it is possible to reach under</p><p>the panel and with a small screwdriver reach the “F” trimmer screw. (Be sure power is off).</p><p>To check the receiver settings, drain all the fuel from the aircraft and jack the tailwheel up</p><p>onto a platform until the bottom of the wing tanks are level. Be sure parking brake is “On” as the</p><p>tail is quite high in this position. Sighting fore and aft along the tank bottom with the line of sight</p><p>meeting the horizon is an easy way to determine when the bottom of the wing tanks are level.</p><p>Level the wing tips by placing a barrel and boards under the low wing tiedown ring until both wing</p><p>tips are on the horizon.</p><p>Then remove the L/H fuel line from the tank and cap the L/H tank outlet and plug the line</p><p>to isolate the two tanks. Set the needle on “E” with the adjust screw on the face of the receiver.</p><p>Gradually add fuel to the R/H wing tank with the battery switch “On” and the fuel receiver switch</p><p>on “R/H”. The battery should be fully charged for this check.</p><p>The receiver needle should start to move very slightly off the “E” mark after 1 to 2 gallons of</p><p>fuel have entered the tank. Then switch the fuel receiver to “L/H” and gradually add fuel to the</p><p>L/H tank. When approximately 4 to 6 gallons have entered the tank the needle should move</p><p>slightly off the “E” mark. To check the “F” mark, lower the tailwheel to the ground and fill both</p><p>tanks completely full. Adjust the trimmer screw behind the panel until both tanks show “F”. Due</p><p>to slight differences in resistance in the senders, one tank may show “F” with the needle at the</p><p>bottom side of the ”F” mark, and the other tank at the top side.</p><p>FUEL SYSTEM DRAINS</p><p>The wing tanks have Curtis CCA-1650 drain valves. If the valves leak, remove them and</p><p>check the seals for nicks or look for trash between the seal and the valve seat. Apply some 3H</p><p>permatex or equivalent to the threads of all drains before they are re-installed. If the seals need</p><p>replacing, the entire valve must be replaced, as Curtis will not sell the seals.</p><p>The header tank drain is a Curtis CCA-39000 and is stainless. It should be activated daily.</p><p>This is the most important drain in the system. Be careful not to cross-thread drains when</p><p>replacing.</p><p>Maintenance Page 16 Air Tractor, Inc.</p><p>September 15, 1989 AT-401</p><p>FUEL SYSTEM SCREENS AND FILTERS</p><p>Each wing tank has a finger strainer soldered to the 90o elbow at the tank outlet. This screen</p><p>should be removed and cleaned at least once a year during the annual inspection. The wobble</p><p>pump incorporates a fine screen and this screen should be removed and cleaned at least every</p><p>annual inspection.</p><p>FUEL WOBBLE PUMP</p><p>The wobble pump is a military surplus U.A.P. Type D-2 that has been overhauled and</p><p>modified in accordance with drawings 50542 and 50157. The modification involves the</p><p>substitution of O-rings for the usual packing around the wobble pump arm. These O-rings will</p><p>wear slightly in time and if there is evidence of leaking around the wobble pump arm, the O-rings</p><p>should be replaced. There are three AN6227-9B O-rings on the wobble pump shaft, and can be</p><p>replaced by removing the arm and the knurled nut on the outboard side of the wobble pump.</p><p>AILERONS</p><p>The ailerons are all-metal and require very little maintenance. The lead counterweight will</p><p>sometimes loosen on the long AN3-33A bolt through the lead and the support tube. If this is the</p><p>case it would be advisable to remove the counterweight and support tube and drill and ream for a</p><p>larger bolt. To do this remove the aileron from the aircraft by removing the nuts from the three</p><p>hinge fittings, removing the four screws in the inspection plate where the push-rod attaches to the</p><p>wing bellcrank, and removing the nut from the bolt through the bellcrank and push-rod. Note that</p><p>there is a spacer washer between the aluminum hinge and the support arm bearing, and that</p><p>there is a AN970-4 large washer on the outboard side of the bearing under the bolt head.</p><p>With the AN4-10A bolts pointing inboard, the correct order of parts would be a AN970-4</p><p>washer under the bolt head, then a AN960-416L washer, then the bearing then a AN960-416</p><p>washer, then the aluminum aileron hinge, then a AN960-416 washer, then a AN365-428A nut.</p><p>The steel inboard hinge uses an AN4-25A bolt, with a AN960-416 washer under the head, then</p><p>the steel hinge, then the bearing, then a AN970-4 washer, then a AN960-416 washer, then a</p><p>AN365-428A nut. Leave the push-rod attached to the aileron and reach through the inspection</p><p>plate opening and remove the bolt attaching the push-rod to the wing bellcrank. Be sure to have</p><p>someone holding up on the aileron trailing edge, and the control stick lock should be in</p><p>place.Then remove the center hinge bolt, with someone at each end of the</p><p>aileron, remove the two</p><p>outboard bolts, lift up on the push-rod to keep it from dragging, and remove the aileron from the</p><p>aircraft.</p><p>The counterweight support tube is p/n 20279-1 and can be removed from the aileron by removing</p><p>the two plug buttons on the upper and lower side of the aileron nose skin and removing the AN3-</p><p>12A bolt that attaches the support tube to the support structure that is riveted to the aileron. The</p><p>counterweight and support tube can then be taken to the workbench where the long AN3-33A bolt</p><p>is removed. Leaving the parts together, clamp the counterweight to the base of the drill-press,</p><p>using a long 3/16" drill bit chucked in the drill press align the spindle with the 3/16 hole through</p><p>the counterweight and support tube. Then change to a 7/32" drill bit and enlarge the hole. Then</p><p>ream .248 through both parts. Grease the new AN4-33A bolt and install. Re-install</p><p>the counterweight and support tube on the aileron and check for a snug fit. The AN3 bolts have a</p><p>torque of 60 inch-pounds applied at the nut, the AN4 bolts have a torque of 100 inch-pounds</p><p>applied at the nut. Re-install the aileron in the reverse order as removed, taking care that the</p><p>washer arrangement is correct. The bolt through the push rod and wing bellcrank is an AN4-12A</p><p>with a AN960-416 washer under the head and one under the AN365-428A nut.</p><p>While the aileron is removed, check the aluminum hinges for secure attachment to the spar,</p><p>and check the steel hinge for signs of corrosion, or loose rivets, or cracks in the welded areas.</p><p>Inspect both ends of the push-rods for cracks in the threads, check the rod-end bearing (Fafnir</p><p>RE4F6-2) for condition and lubrication, and be sure the check nut against the bearing is snug.</p><p>After the aileron has been re-installed and an inspection of all connections has been made,</p><p>reach through the inspection plate opening and check to see if the push-rod is free to rotate</p><p>slightly as the aileron is moved through the full range of travel. After being sure the bolt through</p><p>the push-rod and wing bellcrank has been torqued, re-install the inspection plate with the four</p><p>screws.</p><p>The bearings in the aileron support arms are Fafnir KP4A and make a press-fit into the 1/4"</p><p>aluminum arm, and are staked on both sides. These bearings are sealed, require no lubrication,</p><p>and should not require replacement in service.</p><p>FLAPS</p><p>The flaps are attached to the 3/8" aluminum flap arms with AN4-24A bolts. The order of</p><p>washers and parts with the bolts pointing inboard is a AN970-4 large washer under the bolt head</p><p>(except at the boom hangar location where a AN960-416 is used), then the bearing (Fafnir KP4),</p><p>then the steel flap arms, then a AN960-416 washer, then a AN365-428A nut.</p><p>The flap push-rod is attached to the flap with a AN4-25A bolt which is pointing outboard,</p><p>and the order of parts is AN970-4 washer under the bolt head, then the steel flap arm, then two</p><p>AN960-416 washers, then a AN365-428A nut. The push-rod has an adjustable Fafnir RE4M6</p><p>bearing with a AN316-6 check nut. Be sure that the RE4M6 bearing is positioned to allow the</p><p>push-rod to be rotated slightly from side to side.</p><p>During annual inspections, the AN4-25A bolt through the push-rod should be checked for</p><p>straighness, and if bent, both the bolt and bearing should be replaced immediately. As a precau-</p><p>tion against a fatigue failure, the RE4M6 bearing in the flap push-rod should be changed at least</p><p>every 2,000 hours, since a large man standing on the flap trailing edge exerts a considerable force</p><p>on the push-rod, which puts a bending force on the threads of the bearing. At 100 hour intervals,</p><p>remove the lower fuselage side skins under the cockpit and while the flaps are being cycled</p><p>through the full range of travel, check to see if the push-rod drags on any fuselage parts. With the</p><p>flaps full down, move the ailerons through the full range of travel and check clearence between</p><p>the flap push-rod and the ailerons through the full range of travel and check clearance between</p><p>the flap push-rod and the aileron push-rod. If the tubes touch, check flap rigging as the 26o down</p><p>travel has probably been exceeded.</p><p>Air Tractor, Inc. Maintenance Page 17</p><p>AT-401 April 1, 1998</p><p>AILERON AND FLAP RIGGING</p><p>With the flap actuator in the “Up” position, the flap push-rods are adjusted so that the lower</p><p>side of the flaps form a straight line with the lower side of the fuel tank at station 61.0. Flap</p><p>travel from this point is then set at 26o (+/- 1 1/2o). Flap markings on the flap are located opposite</p><p>the wing flap bay upper skin so that the pilot will view the markings at 10o, 20o, and at full travel.</p><p>The ailerons are rigged with the trailing edge 1/8" to 3/16" below the flap trailing edge so</p><p>that flight loads will bring the trailing edge up approximately even with the flap trailing edge.</p><p>Aileron travel (with flaps up) is 20o up (+/-1o) and 14o down (+/-1o). Aileron control stops are</p><p>located under the cockpit floor on each side of the torque tube horn. The adjustment consists of</p><p>tightening or loosening the bolts that compress a stack of 6 to 7 neoprene washers (p/n 70067-1).</p><p>The neoprene washers act as shock absorbers for the control system, but sometimes split and fall</p><p>out, so it is advisable to inspect the stops during annual inspections.</p><p>The aileron and flap control system components under the cockpit floor are rigged as</p><p>follows:</p><p>1. Set the control lock on the stick. Flaps full up.</p><p>2. Check the length of the push-rod assembly (p/n 70014-2) that connects the flap torque</p><p>tube to the 90o bellcrank. It should measure 6.65" from bearing hole to bearing hole.</p><p>3. Check the length of the push-rod assembly (p/n70014-4) that connects the 90o bellcrank</p><p>to the rectangular welded support frame assembly (p/n 70072-1). It should measure</p><p>13.78".</p><p>4. Check the length of the push-rod assembly (p/n 70014-3 that connects the aileron control</p><p>horn to the 180o bellcrank. It should measure 14.88".</p><p>5. With all push-rods the correct length, the 70072-1 support frame assembly should clear</p><p>the fuselage vertical tube at the bottom approximately 1/4".</p><p>6. The push-rod assembly (p/n 70014-1) that connects the wing bellcrank to the aileron will</p><p>be approximately 10.69" long but this is the push-rod that is adjusted to provide the</p><p>necessary trailing edge setting with respect to the flap.</p><p>AILERON AND FLAP BELLCRANKS AND SUPPORTS</p><p>The 180o bellcrank under the cockpit floor is p/n 70076-1 and is interchangeable right to</p><p>left. The welding operation on these bellcranks sometimes causes a slight warp which will reduce</p><p>the clearance from the 70072-1 support frame, so if the bellcranks are changed, be sure there is</p><p>ample clearance and if necessary reverse the direction of the AN24-19A clevis bolt that connects</p><p>the push-rods to improve clearance. These bellcranks have Fafnir KP6A bearings installed with a</p><p>70081-2 stainless spacer that allows the AN4-42A bolt that connects the bellcrank to the support</p><p>frame assembly to be fully torqued (100 inch-pounds at the nut).</p><p>The support frame (p/n 70072-1) is attached to the floor structure with a AN4-50A bolt.</p><p>There are two Fafnir KP6A bearings in the support frame and a 70081-1 stainless bushing allows</p><p>full bolt torque same as with the 70076-1 bellcrank. The KP6A bearings are sealed and require no</p><p>lubrication. Some end play will develop due to tolerance accumulation, but up to .040” is</p><p>acceptable.</p><p>Maintenance Page 18 Air Tractor, Inc.</p><p>September 15, 1989 AT-401</p><p>The aileron bellcranks in the wings are attached to a welded structure with an AN4-46A bolt</p><p>and have a p/n 70081-3 stainless spacer to allow full bolt torque. Bearings are Fafnir KP6A. The</p><p>wing bellcranks are p/n 70079-1 (L/H) and 70079-2 (R/H). Maximum end play of the wing</p><p>bellcrank is .03". The bolt attaching the wing bellcranks may be reached by removing the plug</p><p>buttons (11/16) on the top and bottom skins. To remove the bellcrank from the wing it is</p><p>necessary to remove some rivets attaching the lower wing skin. Remove rivets that can be easily</p><p>reached for re-installation.</p><p>The 90o bellcranks that connect to the flap torque tube are p/n 70082-1 and are inter-</p><p>changeable R/H to L/H. They are connected to the fuselage frame with AN6-34A bolts and a p/n</p><p>70085-1 spacer bushing to allow full torque of 300 inch-pounds to be used during bolt installa-</p><p>tion. At each end of the spacer bushing is a 90011-1 large washer to contain the Torrington p/n</p><p>B812 needle bearing. These needle bearings should be checked, cleaned, and packed with general</p><p>purpose grease once a year during annual inspections. During re-assembly, make sure the</p><p>70085-1 spacer bushing has been faced off square on each end because if it is not, the slight</p><p>chamfer or bevel will cause the 90011-1 washer to distort and drag the bellcrank face. With the</p><p>AN6-34A bolt fully torqued, there should be positive clearance between the 90011-1 washers and</p><p>the bellcrank, with end play not to exceed .03". Check the bellcrank end for excessive wobble</p><p>which would indicate a worn needle bearing, spacer bushing, or both. The needle bearing should</p><p>hand press-fit into the bore of the bellcrank, and the spacer bushing should be a loose sliding fit</p><p>inside the needle bearing. The bolt should make a loose sliding fit on the spcer bushing. While the</p><p>bellcrank is removed, check for any sign of bending of the plates or cracks in welds. These</p><p>bellcranks are subject to bending if the aircraft is parked with the tail into a high wind and the</p><p>ailerons begin a flutter motion even though the stick is locked. If the bellcranks are bent, replace</p><p>them.</p><p>The flap torque tube is attached to the fuselage frame with two AN4-10A bolts. The bearings</p><p>which are pressed into the torque tube fittings and staked are NMB p/n ABT4 and are spherical</p><p>bearings with a stainless ball and a teflon lining. As this type of bearing has some drag, be sure</p><p>the AN4-10A attach bolts are fully torqued. These bearings do not require lubrication. The 2.0"</p><p>diameter flap torque tube consists of the welded assembly and bearings only. At the extreme end</p><p>of each side of the torque tube is a 1/4" aluminum arm (p/n 70027-1) which also has a NMB p/n</p><p>ABT4 bearing installed. The two flap push-rods attach to the bearings with AN4-10A bolts and</p><p>should be torqued to 100 inch-pounds at the nut same as the fuselage attach bolts.</p><p>Two smaller 1/4" aluminum arms attach the torque tube to the flap actuator “Tee”. These</p><p>arms are p/n 70032-1 and have a KP6A bearing pressed into place and staked.</p><p>FLAP ACTUATOR</p><p>The flap actuator assembly is a Commercial Aircraft Products p/n D-145-00-35. This actua-</p><p>tor uses micro-switches to limit the down and up travel to the flaps. The micro-switches are p/n</p><p>BZ2R5551-A2 and the arm with the roller attached that actuates the mirco-switch is an AN3169-</p><p>1 arm. The motor for the actuator can be purchased separately and is p/n C-145-250-1. The</p><p>actuator assembly attaches to the fuselage frame with an AN4-16A bolt. At this connection there</p><p>is also a 70026-1 spacer bushing and a Bunting P31-8 bronze bushing. If the actuator is replaced</p><p>or removed, be sure both bushings are in place.</p><p>Air Tractor, Inc. Maintenance Page 19</p><p>AT-401 April 1, 1998</p><p>The actuator assembly has a threaded collar. This collar is threaded internally to match the</p><p>threads on the worm drive threads of the actuator, and is threaded externally to match the</p><p>threads of the Air Tractor “Tee” assembly which is p/n 70037-1. The “Tee” assembly is attached</p><p>to the two 1/4" aluminum 70032-1 arm assemblies that are bolted to the flap torque tube</p><p>assembly. The “Tee” assembly has a steel grease shield and cap attached. The shield is p/n</p><p>70039-1 and is attached to the “Tee” with two AN500A5-3 screws. The cap is a 1 1/8 SC. Caplug</p><p>attached to the shield with a TY-525 Tyrap.</p><p>The “Tee” assembly that screws into the Threaded collar has a AN565D6H4 set screw that is</p><p>located on the top surface of the “Tee”. The threaded collar has a large diameter rounded surface,</p><p>and just forward is a smaller diameter part on the collar that is to be used for tightening the</p><p>collar against the “Tee”. Whenever it is necessary to remove the flap actuator, the factory practice</p><p>is to first loosen the set screw in the “Tee” assemlby with a small Allen wrench, then place a soft</p><p>rag or duct tape on the small diameter of the threaded collar so as not to scratch the finish and</p><p>with a pair of water-pump pliers or vice-grips, break loose the connection between the threaded</p><p>collar and the “Tee” assembly. Then the threaded collar can be screwed by hand from the “Tee”.</p><p>CAUTION: Have someone hold up on the flap trailing edge so the flaps will not fall down against</p><p>the boom hangers.</p><p>See the section “Flap Actuator Trouble Shooting” for a step by step procedure for removing</p><p>the actuator assembly from the aircraft.</p><p>Entrance inside the fuselage is made easier by removing the lower R/H pulley next to the</p><p>header tank so that the rudder interconnect cable will not be in the way, and entering the</p><p>fuselage from the R/H side. Remember that there is a washer under the pulley when it is re-</p><p>installed.</p><p>All wires from the flap actuator assembly have Wristlock connections so that it is not</p><p>necessary to cut or splice wires when the actuator is removed. Also, it is possible to replace the</p><p>motor without removing the actuator assembly.</p><p>FLAP ACTUATOR TROUBLE SHOOTING</p><p>If any trouble develops, first check the flap circuit breaker on the panel. If this does not</p><p>produce any results, a visual inspection of the mico-switches and micro-switch arms should be</p><p>made. Enter the fuselage as described before and inspect the micro-switches for broken actuator</p><p>arms or loose wires. The flaps can be retracted by rotating by hand the rubber coupling at the</p><p>motor shaft. This is slow, but the flaps can be raised this way.</p><p>If the flaps are up but won’t go down, chances are there is something wrong with the down</p><p>micro-switch. If the flaps are down but won’t go up, look for trouble with the up micro-switch.</p><p>The flap micro switches have a 60635-1 diode assembly accross the NC and C switch terminals.</p><p>This diode greatly increases the life of the switch. Before checking the switch remove the diode</p><p>and check it as follows: With an ohm meter check continuity through the diode. It should read</p><p>near infinity with the leads one way and near zero with the leads reversed. If the diode is shorted</p><p>or open replace it. When installing the diode be careful to observe the polarity. The negative side</p><p>of the diode is marked with a stripe and the stripe corresponds with the vertical line on the diode</p><p>symbol on the schematic.</p><p>If the flap goes down past the 26o mark, check the down micro-switch. Have someone cycle</p><p>the flaps and see if the roller on the micro-switch arm lifts properly on the striker plate and</p><p>pushes in the micro-switch plunger to stop the travel. If there is any doubt, push the plunger in</p><p>Maintenance Page 20 Air Tractor, Inc.</p><p>May 2, 1994 AT-401</p><p>with the flap midway through the stroke. If the switch is working, the flap will stop. In this case,</p><p>the down micro-switch needs to be re-positioned to activate the micro-switch.</p><p>Check the micro-switches with an Ohmmeter. Before checking continuity with the Ohmme-</p><p>ter remove the diode assembly. Check continuity between the “C” pin and the “N.C.” pin on both</p><p>switches. Activate the switch by pushing the plunger in and check continuity between the “C” pin</p><p>and the “N.O.” pin. If these checks are positive, the micro-switches are OK and do not need to be</p><p>changed. If a switch is bad, change it. See drawing 60198 for flap system wiring schematic.</p><p>The actuator jack screw is fitted with a stop to mechanically limit the ball nut travel in case</p><p>of a problem with the down micro switch. If you replace the actuator, the new one will come with</p><p>a new stop nut. To install the stop nut, first install the p/n 70037-1 "tee nut", that was installed</p><p>on the old actuator. Install the AN565D6H4 set screw. Now that the Tee nut is installed, install</p><p>the left hand thread stop nut with Loctite RC-609. The roll pin hole has already been drilled.</p><p>Torque the stop nut until</p><p>April 20, 2005April 20, 2005April 20, 2005April 20, 2005April 20, 2005</p><p>The leading edge is extra heavy with a leading edge doubler bonded internally to minimize</p><p>denting. Each wing panel has the leading edge divided into five different pieces to allow easy</p><p>replacement. Universal head rivets are used to facilitate the removal and replacement of leading</p><p>edge sections.</p><p>The fuel tanks are located in the inboard section of the wing and are an integral part of the</p><p>structure. The closely riveted seams and heavy skins make them burst resistant in the event of a</p><p>crash. Sealing is accomplished by an application of Product Research PR-1422A2 sealing com-</p><p>pound*. The inboard end of the wing is sealed against chemical entry and the aileron pushrod</p><p>has a flexible boot attached to prevent entry of chemical at the pushrod location. A complete wire</p><p>bundle for night working lights is installed inside the wing during assembly so that lights may be</p><p>added at a later date.</p><p>The upper spar cap is painted with yellow polyurethane paint and the lower spar is cad-</p><p>mium plated and primed with Chromanoxide primer for corrosion protection. All other parts</p><p>inside the wing are treated with alodine and primed with zinc chromate primer prior to assembly.</p><p>* Alternate sealer is TBM PKMMC236A1/2</p><p>AILERONSAILERONSAILERONSAILERONSAILERONS</p><p>The ailerons are of all-metal construction and hinged on ball bearings. The bellcranks and</p><p>pushrod ends operate on ball bearings, producing smooth operation and low system friction. The</p><p>stick forces are light and the ailerons are very responsive. The light stick forces are a result of the</p><p>installation of aerodynamic servo tabs installed on the outboard end of each aileron.</p><p>The ailerons are interconnected with the wing flaps so that as the flaps move down through</p><p>26°, the ailerons droop 9°. The interconnection is non-linear so that most of the aileron droop</p><p>occurs with the first half of the flap travel. This provides optimum conditions for short take-off</p><p>performance.</p><p>Each aileron has a large balance weight on the outboard end of the aileron just forward of</p><p>the leading edge. These weights must never be removed as they are necessary for flutter preven-</p><p>tion.</p><p>FLAPSFLAPSFLAPSFLAPSFLAPS</p><p>Extra large Fowler-type flaps are incorporated on the Air Tractor. The flaps are electrically</p><p>operated and may be stopped at any position from 0° to the maximum of 26° travel. The flaps are</p><p>controlled by a switch conveniently mounted just below the throttle quadrant. The flaps have</p><p>external markings which may be viewed from the cockpit with each of the first two marks being</p><p>10° of travel.</p><p>The flaps are very effective for both take-off and landing. For a short take-off roll, 10° of flap</p><p>is normally used. The flaps are also useful during turns, although generally less than 10° is used.</p><p>EMPENNAGEEMPENNAGEEMPENNAGEEMPENNAGEEMPENNAGE</p><p>The horizontal stabilizers are all-metal and strut-supported for rigidity. The struts are</p><p>constructed of streamlined 4130N tubing. The struts have a stainless clevis where the attachment</p><p>to the stabilizer is made and the clevis is adjustable in order to rig the stabilizers properly with</p><p>the wing and in a straight line from side to side.</p><p>Description Page 2Description Page 2Description Page 2Description Page 2Description Page 2 Air Tractor, IncAir Tractor, IncAir Tractor, IncAir Tractor, IncAir Tractor, Inc</p><p>April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998 AT-401AT-401AT-401AT-401AT-401</p><p>The vertical fin is cantilever and is of all-metal construction. A heavy-duty wire deflector</p><p>cable is attached to the top of the vertical fin and extends to the top of the canopy where it is</p><p>anchored.</p><p>The control surface hinges have a single stainless steel ball with a Teflon lining. Long</p><p>bearing life can be expected and it is not necessary to lubricate the hinge.</p><p>The elevator trim tabs act as Servo tabs in addition to providing longitudinal trim for the Air</p><p>Tractor. Because of the large tab size, the trim tabs provide a considerable amount of trim</p><p>authority. Removable bronze bushings are provided at each point so that trim tab free play may</p><p>be kept to a minimum. The all-metal rudder has a servo tab that also serves as an adjustable</p><p>trim tab.</p><p>LANDING GEAR AND BRAKESLANDING GEAR AND BRAKESLANDING GEAR AND BRAKESLANDING GEAR AND BRAKESLANDING GEAR AND BRAKES</p><p>A spring type main and tail landing gear is used on the Air Tractor. This type of landing gear</p><p>provides a minimum of maintenance, low drag and considerable energy absorption for hard</p><p>landings. In addition, a very smooth ride is provided for operations from rough strips.</p><p>The main gear axles are made of 4130N steel, heat treated, and cadmium plated for</p><p>corrosion protection. Tapered aluminum shims are used between the axle and the main gear leg</p><p>to provide the proper camber and toe-in. The main gear wheels are Cleveland p/n 40-234 with an</p><p>8.50 x 10 8-ply rating tire installed. Brakes are Cleveland 30-18400 L/H and 30-18450 R/H.</p><p>Main wheel tire inflation pressure is 41 lbs. unloaded or 43 lbs. loaded.</p><p>The optional AT-402A main gear wheels are Cleveland p/n 40-133 with a 29 x 11.00 10 ply</p><p>rating tire installed. Brakes are the same, left or right and are Cleveland p/n 30-98C. Inflation</p><p>pressure is 50 psi (unloaded) or 52 psi (loaded).</p><p>The tail wheel is a Cleveland p/n 40-168. A grease fitting is provided in the side of the wheel</p><p>in order to grease the bearings. The tail wheel tire is a 5.00 x 5, 6-ply rating. Tire pressure is 50</p><p>pounds loaded.</p><p>The tail wheel fork is of welded 4130N tubing construction. Bronze bushings and a brass</p><p>wear plate are incorporated where the fork enters the tail wheel housing. A tail wheel locking</p><p>mechanism is provided and the tailwheel may be unlocked by pushing the stick full forward. This</p><p>lifts the stainless locking pin out of the tail wheel fork and allows the tail wheel assembly to</p><p>swivel 360°. If during taxi the aircraft tends to steer to the left or to the right with the controls</p><p>neutral, it is possible to readjust the lock pin position by loosening the 4 screws that attach the</p><p>lock pin housing to the fork housing plate. The lock pin can then be moved in the desired</p><p>direction and the screws tightened.</p><p>ENGINEENGINEENGINEENGINEENGINE</p><p>The AT-401 is powered by either a Pratt & Whitney R1340 AN-1 or R1340 S3H1 radial nine-</p><p>cylinder engine. The engine is supercharged and normally incorporates a blower having a rota-</p><p>tional speed of ten times crank shaft RPM. For operators who work consistently above 5,000 feet</p><p>MSL a blower turning twelve times crankshaft RPM may be installed.</p><p>The R1340 has a take-off rating of 600 horsepower (five minutes) at 2250 RPM and 36.0</p><p>inches manifold pressure. Maximum continuous rating is 550 HP at 2200 RPM and 34.0 inches</p><p>manifold pressure. These are sea-level ratings and at 5,000 ft. the maximum continuous rating is</p><p>550 HP at 2200 RPM and 32.5 inches of manifold pressure.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Description Page 3Description Page 3Description Page 3Description Page 3Description Page 3</p><p>AT-401AT-401AT-401AT-401AT-401 April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998</p><p>The engine mount is a “Vibro-damp” mount which incorporates four vibration isolators</p><p>around the perimeter of the engine mount ring. These isolators are p/n 2034 and are clamped to</p><p>the engine mount structure. The isolators are very durable and should last the life of the aircraft.</p><p>The engine mount structure is a series of “X” braces which result in a very rigid frame, and</p><p>for this reason, the firewall attachments have to line up perfectly with the fuselage frame. To</p><p>accomplish this, removable eccentric bushings are installed in the engine mount at the firewall</p><p>attachment. In most cases, two or more of the engine mount legs line up with the fuselage frame</p><p>with concentric bushings in place, and the eccentric bushings are used in only one or two</p><p>locations. The bushings are</p><p>the hole in the nut aligns with the hole in the threaded end of the jack</p><p>screw. Install the roll pin. Install the shield with the AN500A5-3 screw and lock washer. Be</p><p>sure not to leave out the lock washer. Safety wire the screws.</p><p>Flap Actuator Removal Instructions:</p><p>1. Disconnect all wires at Wristlock connections in wire harness and identify wires for re-</p><p>assembly.</p><p>2. Remove the 4 AN4 bolts that attach the aluminum arms on the flap “Tee” to the torque</p><p>tube.</p><p>CAUTION: Have someone hold up on the flap trailing edge before the last bolt is removed.</p><p>3. Remove the nut and washer from the AN4 bolt attaching the actuator assembly to the</p><p>fuselage frame.</p><p>4. Remove the AN4 bolt, paying close attention to the spacer bushing inside the bronze</p><p>bushing, and lower the flaps to rest on boom hangers.</p><p>5. Check rubber coupling on motor shaft for excessive back-lash</p><p>With the complete actuator on the work bench, if it is desired to change the actuator itself,</p><p>perform the following.</p><p>1. Remove the two screws that hold the dust shield to the lower end of the assembly.</p><p>2. Use open end wrench to remove down over-ride stop from end of jack-screw. CAUTION:</p><p>This stop is left-hand threads.</p><p>3. Loosen the set screw in the top of the “Tee” assembly with a small Allen wrench.</p><p>4. With water-pump pliers or vice-grips, breake loose the collar from the “Tee” assembly.</p><p>5. Unscrew striker by hand out of “Tee assembly.</p><p>Flap Actuator Installation Instructions:</p><p>1. Re-install actuator in aircraft in reverse order as removal.</p><p>2. Raise flaps to full up position with flap switch in cockpit. Check position of flaps relative</p><p>to wing (See Flap and Aileron Rigging section of this manual).</p><p>3. With flaps properly positioned with respect to the lower side of the wing there should be a</p><p>gap 1/16" to 1/8" between the striker and the end of the up travel (See Note 5, drawing</p><p>70031). If the gap is not within the range above, use the flap switch in the cockpit to</p><p>provide the proper gap. Then it will be necessry to set the flap position with respect to the</p><p>lower wing surface by adjusting the flap push-rods.</p><p>Air Tractor, Inc. Maintenance Page 21</p><p>AT-401 April 1, 1998</p><p>4. Then loosen the two screws holding the UP micro-switch and adjust the micro-switch until</p><p>a click is heard. Tighten the two screws and once more use the flap switch in the cockpit</p><p>to lower and then raise the flaps to the full up position. Again check the gap between the</p><p>striker and the end of the up travel for 1/16" to 1/8" travel. Check position of flaps with</p><p>respect to the wing lower surface. If all is in order, proceed to set the down micro-switch.</p><p>5. Extend the flaps to 26o and adjust the lower micro-switch until a click is heard. Re-cycle</p><p>the flaps and check down travel again.</p><p>6. Re-check the position of the UP micro-switch two ways: Raise the flaps all the way with</p><p>the flap switch. After the flaps are fully retracted continue to hold the flap switch up and</p><p>observe the voltmeter. If the voltmeter shows excessive voltage drop, the micro-switch has</p><p>not turned off the current. If this check is OK, then check the distance between the striker</p><p>and the end of the up travel which should be 1/16" to 1/8" as mentioned in steps 3 and 4.</p><p>FLAP MOTOR TROUBLE SHOOTING</p><p>If the micro-switches appear OK the flap motor may be checked as follows:</p><p>1. Slide the conduit down from the wire splice (Wristlock) where the yellow and black wires</p><p>go into the wire bundle.</p><p>2. Note which wire the black wire from the motor connects to.</p><p>3. Use an outside source of power (24 volts) protected with a circuit breaker. Ground the</p><p>negative power source and attach the positive wire to the black wire. The motor should</p><p>run in one direction. Attach the positive wire to the yellow motor wire and the motor</p><p>should run in the other direction.</p><p>4. If the motor does not respond as described above, it is faulty and should be replaced. It is</p><p>attached to the actuator by two 1032 nuts. Be sure rubber coupling is in good condition</p><p>when motor is replaced.</p><p>HORIZONTAL STABILIZERS</p><p>The horizontal stabilizers require very little maintenance since they are all metal. They are</p><p>attached to the fuselage frame with two NAS1304-8 bolts which have a washer under the head</p><p>and two under the nut. On annual inspections the gap cover should be removed from the</p><p>stabilizer and the bolt condition and torque checked. At the same time inspect the fuselage</p><p>fittings closely for cracks. Torque is 100 inch-pounds at the nut. The gap covers are attached with</p><p>90008-1 stainless self-tapping screws which are Phillips trusshead #4x1/4" long. A No. 39 hole is</p><p>drilled for the screw installation. The P580001 rubber channel is a Cessna part and is attached</p><p>with 3-M 8001 Adhesive.</p><p>The stabilizer is sealed on the ends with PR1422A1/2 to prevent chemical entry. There are</p><p>two eyebolts that attach to a welded steel brace inside the stabilizer. The eyebolts are for strut</p><p>attachment and both eyebolts are AN47-22A for s/n 401-0701 and up, and AN44-17A (rear) and</p><p>AN44-21A (front) through 401-0700. WARNING: For planes through s/n 401-0700 the AN44-17A</p><p>and AN-44-21A eyebolts should be replaced after 1,350 hours TIS and thereafter at 1,350 hour</p><p>intervals in accordance with service letter #129. Under each nut are two AN960-716 washers and</p><p>the nut is a AN365-720. The factory procedure is to align the face of the eyebolts with the strut</p><p>clevis before the nut on the eyebolt is fully torqued (550 inch-pounds). Above the nut is a 7/8</p><p>plug bottom (TRW p/n SS-48155).</p><p>There is a p/n 30137-1 (L/H) and 30137-2 (R/H) trim control idler attached to each</p><p>stabilizer rear spar on the inboard end. Each trim idler has two Bunting P26-10 bushings press</p><p>fit inside the welded assembly and a p/n 30070-1 spacer bushing allows the AN3-32A attach bolt</p><p>Maintenance Page 22 Air Tractor, Inc.</p><p>August 10, 2003 AT-401</p><p>to be fully torqued (60 inch-pounds at the nut). The brackets that attach the trim idlers are p/n</p><p>30049-1 and 30049-2 but should never need replacing unless the AN3-32A bolt has become loose</p><p>and caused wear in the holes.</p><p>One of the idler arms is attached to the push-rod connected to the trim tab horn and this</p><p>arm has a Bunting P19-1 bushing press-fit into the idler arm. This is the same size bushing in</p><p>the trim tab horn and both should be replaced when excessive trim tab free-play develops. The</p><p>Bunting bushings are oil-impregnated, but if new ones are installed, fill the bushings to overflow-</p><p>ing with general purpose oil and with finger pressure squeeze on the bushing ends to force the oil</p><p>into the small cavities inside the bushings.</p><p>STABILIZER STRUTS</p><p>The stabilizer struts attach to the fuselage frame with a AN6C11A bolt and to the stabilizer</p><p>eyebolts with AN6-11A bolts. There are p/n 30256-1 stainless terminals with AN316C8 check</p><p>nuts at each strut end to allow for adjustment.</p><p>The struts are constructed of 2.36 x 1.00 x .049 413ON streamlined tubing and may be</p><p>repaired if necessary. They are oiled internally through the threaded fittings on the ends, and</p><p>should be re-oiled if repaired. They are grit-blasted, primed with U.S. Paint R9006-K-13 Epoxy,</p><p>and finished with yellow 92-Y-444 Alumigrip paint. WARNING: The forward gusset on the</p><p>inboard end of the struts will erode from having dry fertilizer particles strike the lower aft portion</p><p>of the fuselage structure. Substantial strength reduction of the strut to fuselage connection will</p><p>occur when the gusset is severely eroded. Consult Service Letter #198 for appropriate action.</p><p>STABILIZER RIGGING</p><p>To rig the stabilizers, the elevators must be removed. The factory practice is to adjust the</p><p>terminal in the forwad strut so that approximately the same amount of threads is showing on</p><p>both R/H and L/H struts. The struts are pinned to the fuselage fittings and the stabilizers are</p><p>pinned to the fuselage attach fittings (Don’t forget the washers under each bolt head) but no nuts</p><p>yet. Have someone hold up the stabilizer tips when they are being attached. Then attach the</p><p>struts to the forward eyebolts only. Sight down the stabilizer</p><p>hinge line to see that the hinges on</p><p>both sides of the aircraft line up within .03". Adjust each strut length the same amount until the</p><p>hinges are in line. Then stand directly behind the aircraft on the exact fuselage centerline and</p><p>raise or lower your line of sight until the same part of each stabilizer falls in the line of sight with</p><p>a reference point on the wings. It is likely that the terminal on one strut will have to be</p><p>lengthened a certain number of turns and the opposite strut shortened the same number of turns</p><p>so that the stabilizers line up with the wings.</p><p>Then adjust the terminal at the rear eyebolt on each side so that the bolts can be inserted</p><p>without causing a twist in the stabilizers. All bolts are now in place and it is necessary to re-</p><p>check the hinge alignment from side to side, and re-check the stabilizer position with the wings. If</p><p>all is still in order, install the washers and nuts on all ten attach bolts (five each side). Torque the</p><p>AN4 bolts to 100 inch-pounds on the nut and torque the AN6 bolts to 300 inch-pounds on the</p><p>nut. Then snug the check nuts at the end of each terminal to 290 inch-pounds torque. Take a</p><p>piece of safety wire and insert in the small inspection hole at each terminal location to be sure the</p><p>terminal is screwed into the strut fitting far enough.</p><p>Re-check nut installation on the stabilizer to frame location and install the gap covers with</p><p>the 90008-1 screws. If the rubber channel is loose on the gap cover, re-attach with 3-M 8001</p><p>adhesive before the gap cover is installed.</p><p>Air Tractor, Inc. Maintenance Page 23</p><p>AT-401 June 26, 2000</p><p>VERTICAL FIN</p><p>The cantilever vertical fin is attached to the fuselage frame at the front spar location with</p><p>two NAS1306-13 bolts and AN365-624 nuts. It has been found that these two bolts tend to loosen</p><p>in service. No doubt buffeting from the propeller slipstream during run-up and stresses from</p><p>turns tend to produce constant loads from side to side that tend to loosen the nuts.</p><p>Check the torque on the two NAS1306-13 bolts at 100 hour intervals. If the bolt is held</p><p>stationary and the torque wrench applied to the nut, the torque value should be 420 inch-</p><p>pounds. For the reverse of this procedure, torque should be 460 inch-pounds.</p><p>The rear spar attaches to the fuselage frame with AN3 bolts of various lengths, depending</p><p>on the amount of shims required between the fuselage frame and the rear spar. The shims are of</p><p>various thickness (.063, .080, .125) and the upper shims are combinations of p/n 30159-1, -2, or</p><p>-3 while the lower shims are combinations of p/n 30160-1, -2, or -3.</p><p>The vertical fin rear spar is drilled on installation where the attachment is made to top</p><p>longeron. If a new fin is installed, make a drill template from the original fin rear spar in order to</p><p>drill the four 3/16" holes for the attachment to the upper longeron. The template should be 2.44"</p><p>wide and long enough to pick up the two lower attach bolts. The template should be made of</p><p>either aluminum or steel, at least .063" thick.</p><p>Install the fin on the aircraft and install the bolts at the front and rear spar locations. Be</p><p>sure the correct amount of shims is used between the fuselage frame and the rear spar. The</p><p>NAS1306-13 front spar bolts have a torque of 420 inch-pounds at the nut. The rear spar bolts</p><p>have a torque of 60 inch-pounds at the nut.</p><p>RUDDER</p><p>The rudder is attached to the vertical fin with three AN4-10A bolts, with a AN960-416</p><p>washer under the bolt head, and two washers under the AN365-428A nut. The rudder hinges</p><p>have NMB p/n ABT4 bearings installed, which are staked on each side of the 1/4" thick hinge</p><p>fitting. Since there is a certain amount of drag with these spherical bearings, it is very important</p><p>to fully torque (100 inch-pounds at the nut) the three AN4-10A bolts that attach the rudder to the</p><p>fin. If the bolts are loose, the bolts will turn on the fin hinge brackets and cause the holes to</p><p>become elongated.</p><p>The bearings have little wear, but if it is necessary to replace them, construct a “puller” that</p><p>will apply force to the outer ring of the bearing with the opposing force against the aluminum</p><p>housing. A AN4 bolt though both parts of the “puller” should be tightened until the bearing rim is</p><p>pulled past the stake marks and the bearing comes out of the housing. When the new bearing is</p><p>installed, re-stake with a center punch.</p><p>The rudder horn is p/n 70092-1 and has two p/n 70093-1 bushings installed for wear at</p><p>the cable attachment. The horn is attached to the rudder assembly with two AN4C7A bolts.</p><p>Rudder control stops are at the rudder horn and the rudder travel is 21o Left, +/-1o, or 21o</p><p>Right.</p><p>RUDDER CONTROLS</p><p>The rudder cables are p/n 70095-1 and attach to stainless link plates (p/n 70094-1) at the</p><p>rudder horn with AN4C10 bolts, AN310C4 nuts, AN960C416 washers, MS24665-151 cotters.</p><p>Maintenance Page 24 Air Tractor, Inc.</p><p>April 1, 1998 AT-401</p><p>There are four MS24566-3B pulleys in the rudder cable system to the cockpit.</p><p>In the cockpit, the rudder cables attach to a steel p/n 70096-1 plate which is bolted to a</p><p>p/n 70101-1 aluminum adjust channel. Also attached to the 70096-1 plate is a p/n 70098-1</p><p>cable assembly which interconnects the rudder with the aileron control system. The interconnect</p><p>springs under the cockpit floor are p/n 70103-1 and attach to a MS21255-3LS cable eye.</p><p>MS21251B3S barrel, MS21255-3RS cable eye, AN100C4 thimble and 18-2-G Nicopress sleeve.</p><p>The rudder pedal hanger assembly (p/n 70109-1) slides in the adjust channel and is held in</p><p>place with a D5-10T-303 Faspin. The hanger assembly has a spring attached to pull it forward to</p><p>remove slack from the rudder cable. The spring is attached to an eyebolt in the hanger assembly</p><p>and is p/n 70102-1.</p><p>The rudder pedal castings are p/n 70115-1 (L/H) and 70115-2 (R/H) and may be removed</p><p>by taking out the AN3 bolt through the p/n 1SC Caplug on the inboard end of the hanger</p><p>assembly and removing the AN4-10 bolt attaching the master cylinder strap. The castings should</p><p>be removed at 2,000 hour intervals and inspected for cracks around the bronze bushing (p/n</p><p>70116-1), bushing wear, and general condition. Grease the hanger assembly and slide the casting</p><p>back in place. Be sure to use the AN310-4 castle nut with a MS24665-151 cotter on the AN4-10</p><p>bolt connecting the master cylinder strap. Also, be sure an AN960-416 washer is installed</p><p>between the strap and casting, and work the brake several times to be sure clearance exists</p><p>between the straps and the casting. While the casting is removed, check the condition of the (p/n</p><p>70492-1) bronze bushing in the master cylinder strap (p/n 70490-1). Oil the bronze bushings</p><p>with a general purpose oil before re-installing the bolts.</p><p>ELEVATORS</p><p>The elevators are attached to the stabilizers and to the pedestal in the fuselage with</p><p>AN4-10A bolts, with a AN960-416 washer under the bolt head and two washers under the</p><p>AN365-428A nut except at the pedestal where only one washer is under the nut. The elevator</p><p>horns connect to the aft push-rod with a AN4-10A bolt, two AN960-416 washers (placed to give</p><p>maximum fuselage clearance), and a AN365-428A nut.</p><p>Like the rudder, the elevators and center pedestal have NMB p/n ABT4 spherical bearings</p><p>installed, and due to bearing drag, it is very important for all bolts connecting the elevators and</p><p>the horns to be fully torqued (100 inch-pounds at the nut). We have seen elevator horns with</p><p>badly elongated holes because the elevators had been replaced in the field and the bolts were not</p><p>fully torqued.</p><p>A repair for elongated holes in the horns has been to drill out the holes to 9/32", ream with</p><p>a special .3120 reamer (available at the factory if required), and installing a press-fit 4130N steel</p><p>bushing .3125 to .3130 O.D. x .250 I.D x .080 long. With the bushing in place, heli-arc weld the</p><p>bushing to the horn in two places with 1/8" long weld beads. Then sand, etch, paint with Ag Air</p><p>yellow epoxy.</p><p>To replace the bearings, see the section on “Rudder” for instructions.</p><p>Elevator stops are at the elevator</p><p>horn. The down stop has a p/n 70067-1 neoprene washer</p><p>in compression to absorb shocks and sometimes this washer splits and falls out so during 100</p><p>hour inspections, check to see if this washer is in place. Also, if the control stick is pulled back</p><p>sharply against the up stop or if a wind gust blows the elevator up, the up stop bracket will bend</p><p>and should be straightened if found to be bent.</p><p>Elevator travel is 28o up, 16o down, +/-1o.</p><p>Air Tractor, Inc. Maintenance Page 25</p><p>AT-401 April 1, 1998</p><p>ELEVATOR CONTROLS</p><p>The aft elevator push-rod that connects to the elevator horns is p/n 70020-1 and is</p><p>adjustable on the forward end which has a Fafnir RE4M6 bearing installed. The aft end of the</p><p>push-rod has a NMB p/n ABT 4 bearing same as the elevator and rudder and is pressed into</p><p>place and staked same as in other applications. If it is to be removed, see the “Rudder” section for</p><p>removal instructions.</p><p>The aft elevator idler is p/n 70023-1 and attaches to the fuselage frame with a AN4-17A</p><p>bolt. This idler has two Torrington B 610 bearings installed, with a p/n 70055-1 spacer bushing</p><p>and two 1/4 x 3/4 x 1/16 commercial plated washers on each end to contain the Torrington</p><p>bearings. During annual inspections, this idler should be removed, and the bearings cleaned and</p><p>packed with general purpose grease. Check for excessive wobble on the lower end of the idler</p><p>which would indicate worn bearings, or a worn spacer, or both. When the idler is re-installed be</p><p>sure to grease the bolt before installation and torque to 100 inch-pounds at the nut. After</p><p>installation, check the aft push rod to see that it will rotate slightly in either direction to indicate</p><p>that the RE4M6 bearing is positioned properly, and check the AN316-6 check nut at the bearing</p><p>for snug.</p><p>Also remove the control lock and push the elevator through the full range of travel, checking</p><p>the clearance of the bolt through the elevator horns with the fuselage structure. Since two</p><p>washers are installed on this bolt, one may be under the bolt head, or both may be under the nut,</p><p>depending upon which arrangement gives the best clearance to the fuselage structure.</p><p>Check the position of the eyebolt in the aft idler that the tail wheel lock spring is attached</p><p>to. The spring is International Harvester p/n 54548-D and if the eyebolt is positioned correctly,</p><p>the spring end will slide easily through the eyebolt as the elevator is moved from full down to full</p><p>up. A little grease at this point will help.</p><p>The tail lock cable is p/n 40043-1, attaches to a AN115-21 shackle and MS20392-2-21</p><p>clevis pin at the lock pin lifting arms (p/n 40019-1), is supported by a 40701-00 guide at the tail</p><p>spring clamp and at the upper end attaches to a MS21251-B3S barrel, MS21255-3LS cable eye</p><p>and then to the 54548-D spring mentioned above. The cable passes through a p/n 70126-1 guide</p><p>block where it enters the fuselage. Check the cable for wear at the fairlead, and at the guide block</p><p>location.</p><p>A large aluminum push-rod (p/n 70011-1) connects the aft elevator idler to the forward</p><p>idler (p/n 70117-1). The aluminum push-rod is attached to the lower end of the aft idler with</p><p>AN43B-15A eyebolt with 4 each AN960-416 washers under the head and 4 washers under the</p><p>nut. It attaches to the upper end of the forward idler with a AN4-13A bolt. The push-rod has a</p><p>Fafnir RE4S10 bearing installed with 79-040-187-0937 rollpins in each end. In case the bearings</p><p>wear out they can be replaced, but be sure to order them drilled for assembly. If the aircraft is</p><p>parked outside in a moderate wind with the side skins removed, the aluminum push-rod will</p><p>vibrate excessively, so it is a good idea to have only one side skin removed at a time for working</p><p>outside in the wind.</p><p>The forward idler is attached to the fuselage frame with AN4-50A bolt. Fafnir KP6A bearings</p><p>are installed in each end and a stainless spacer bushing (p/n 70081-1) allows the bolt to be fully</p><p>torqued (100 inch-pounds at the nut). The forward idler will have end play but up to .040 is</p><p>acceptable.</p><p>Maintenance Page 26 Air Tractor, Inc.</p><p>May 2, 1994 AT-401</p><p>COCKPIT CONTROLS</p><p>The control stick assembly is p/n 70049-1 and is attached to the 70050-1 torque tube</p><p>assembly with a AN4-31A bolt. The lower end of the control stick is machined aluminum part</p><p>(p/n 70043-1) which houses two Fafnir KP4 bearings held in place by two p/n 1300-93 snap</p><p>rings. The control stick weld assembly is p/n 70047-1 and is chrome-plated and oiled internally.</p><p>The control stick grip is a Automatic Flagman p/n NAI #135-4</p><p>A p/n 70120-1 push-rod connects the control stick to the forward idler assembly with a</p><p>AN4-13A bolt in each end. The push-rod has Fafnir RE4H6 bearings in each end, attached with</p><p>79-040-187-0937 roll pins. If new bearings are ordered, be sure to specify that they are to be</p><p>drilled for installation.</p><p>The 70050-1 torque tube is supported on each end with a p/n 70160-1 housing assembly</p><p>which attaches to the fuselage frame with AN5-14A bolts and a 70054-1 spacer block between the</p><p>housing and the floor. Each housing assembly has a grease fitting installed and the grease should</p><p>be applied at least during annual inspections. The bronze bushings in the housings are Bunting</p><p>EF1416-16 which may be replaced if required. The bushing is a flange type and after a period of</p><p>time bushing wear will cause fore- and aft slack in the torque tube as the elevators are moved up</p><p>and down with the control stick. The slack may be removed by adding a .010 thick shim (p/n</p><p>3088A which is 7/8 I.D. x 1 3/8 O.D. With the torque tube all the way against the rear flange,</p><p>clearance on the front flange should be between .001 to .005. If the shim is a little too thick, the</p><p>face of the forward flange can be faced off slightly if desired.</p><p>The forward end of the torque tube has a p/n 70149-1 boot and a 70144-1 boot ring</p><p>installed, with 90008-1 screws attaching the boot ring to the floor. On the aft cockpit wall, a p/n</p><p>70148-1 boot, 70142-1 boot ring seal the forward elevator push-rod entrance. The hopper handle</p><p>has a p/n 80168-1 boot with a p/n 70140-1 boot ring, and the spray lever push-rod has a p/n</p><p>80131-1 boot with p/n 70154-1 boot ring. The trim push-rod has a p/n 70070-1 boot and a p/n</p><p>70143-1 boot ring.</p><p>A p/n 70478-1 control lock assembly is attached to two AN42B-4A eyebolts that are part of</p><p>the instrument panel attachment. An Ajax #38 spring keeps the control lock pulled down out of</p><p>the way.</p><p>ELEVATOR TRIM TABS</p><p>The elevator trim tabs are p/n 30055-1 L/H, 30055-2 R/H and attach to the elevators with</p><p>90015-5 screws (Machine screws, stainless, truss head, Phillips, 1032 x 1/2" long). There are</p><p>NAS680A3 anchor nuts installed on the elevators for these screws.</p><p>A p/n 70152-1 push-rod attaches to the trim tab horn and to the idler arm in the stabilizer</p><p>with AN3-6 bolts, AN310-3 nuts, AN960-10 washers, MS24665-151 cotters. Be sure the push-rod</p><p>is positioned with the bend on the fwd end approximately under the elevator spar tube. There is a</p><p>Bunting P19-1 bushing at each joint which should be replaced if the tab free play at the trailing</p><p>edge exceeds .20 inches. If there is still excessive free play check the bolts for wear and check the</p><p>push-rod ends for wear. Install new push-rods if the holes are worn.</p><p>Keep the trim tab piano hinge and joints well lubricated with general purpose oil.</p><p>Air Tractor, Inc. Maintenance Page 27</p><p>AT-401 April 1, 1998</p><p>TRIM TAB CONTROLS</p><p>A p/n 70059-6 trim bellcrank is attached to the fuselage frame with AN3-14A bolts, Bunting</p><p>P26-8 bushings, p.n 70065-1 spacer bushings, AN365-1032 nuts, and AN960-10 washers under</p><p>the nuts. The bellcrank should be removed during annual inspections and the bushings in-</p><p>spected for wear and lubricated.</p><p>The push-rods from the trim bellcrank to the idler arm on the stabilizer rear spar are p/n</p><p>70153-1 and are adjustable. The ends are AN486-4 Clevis ends with AN316-4 check nuts.</p><p>Attachments are with AN3-6 bolts, AN310-3 nuts, AN960-10 washers, MS24665-151 cotters.</p><p>The long push-rod going forward from the bellcrank is p/n 70498-1</p><p>and has a Fafnir</p><p>REB3N bearing attached to the bellcrank with a AN3-7A bolt, AN960-10 washer under the bolt</p><p>head, AN970-3 washer under the nut, AN365-1032 nut.</p><p>Fairleads are p/n 70122-1 with 40081-00 snap rings. The forward end going into the</p><p>cockpit connects to the top hole in the trim lever with the same hardare as connecting to the trim</p><p>bellcrank.</p><p>TRIM LEVER</p><p>The trim lever is p/n Q14-012 Quadrastat. It has a p/n 70063-1 stop installed with slotted</p><p>holes that allow movement up and down to adjust the tab travel. To position the lever in neutral,</p><p>install the control lock, position the lever in the green band, and adjust the forward push-rod</p><p>until the trim tabs are lined up with the elevator trailing edge. The stop can then be moved up or</p><p>down to provide a tab travel of 11o up, 10o down +/-1 1/2o.</p><p>If the trim lever creeps in flight, adjust the stops on each side of the trim lever so that a gap</p><p>of .020" is provided on each side of the lever.</p><p>FUSELAGE REMOVABLE SKINS</p><p>The side skins of the fuselage are attached to the fixed skins with Monadnock studs of</p><p>various lengths. The stud has a basic part number of 1142005 and the dash number designates</p><p>the length. The most common stud is 1142005-3 with the next most common a -4. All studs have</p><p>the dash numbers on the head. Stud lengths used are -3 through -15. Stud installation requires</p><p>a 1142925-2 grommet and a 1142902 snap ring. Installation pliers are needed for stud installa-</p><p>tion or removal. All Monadnock receptacles are p/n 1142715.</p><p>The side skins can be easily removed.</p><p>The side skins have a thin strip of neoprene to prevent chafing. This neoprene is 1/32" thick</p><p>by 1.0" wide, comes in 10 ft. rolls, has pressure sensitive adhesive backing and is p/n NS5565. A</p><p>punch is made of a piece of 3/4" OD tubing and one end sharpened on a grinder. At each</p><p>Monadnock location, the neoprene is marked and a 3/4" hole is punched.</p><p>The side skins are sheared to size, but the Monadnock holes will require drilling on installa-</p><p>tion. The old skin may be used for a pattern, or if it is damaged, ask the factory to provide a hole</p><p>finder. Use a Camloc hole saw .471 diameter to drill the side skins to match the receptacles.</p><p>These hole saws have a No. 30 pilot.</p><p>Maintenance Page 28 Air Tractor, Inc.</p><p>April 1, 1998 AT-401</p><p>FUSELAGE FIXED SKINS</p><p>The fixed skins are attached with 832 machine screws and nuts. Nuts in the lower skins are</p><p>stainless MS21044-C08 and in the upper fuselage areas are AN365-832. The 100o countersunk</p><p>machine screws are p/n 90012-5 for the 832 x 1/2 size, 90012-7 for the 832 x 5/8 size. The</p><p>Truss head machine screws are p/n 90013-3 for the 832 x 3/8 long, -5 for 1/2 long, -7 for 5/8</p><p>long and -8 for the 3/4 long.</p><p>The long lower skin is attached to the skin under the cockpit floor with rivets, but if it is</p><p>desired to remove one skin but not the other, the rivits can be drilled out and replaced with</p><p>90013-3 or -5 screws and stainless nuts. If the baggage floor is to be removed, it is necessary to</p><p>remove the long lower skin, in order to reach the nuts.</p><p>During annual inspections, all screws attaching the fixed skins should be checked to see if</p><p>they are tight.</p><p>The Camloc receptacles are attached to all lower skins and stringers before these parts are</p><p>attached to the aircraft. If a skin or stringer is replaced, be sure to install the side skin and attach</p><p>it to the part being replaced so that it will be properly positioned for the side skins to fit after</p><p>installation to the airframe.</p><p>FUSELAGE COCKPIT SKINS</p><p>The cockpit skins are riveted to the floor and to the support angles with MS20470AD4</p><p>rivets. Attachments to the door frames are CR163-4-4 Cherry rivets. The cockpit skins may be</p><p>removed by drilling out the rivets where necessary and is not a difficult operation. The hopper</p><p>should be removed in order to remove the cockpit floor however.</p><p>FUSELAGE FRAME</p><p>The fuselage frame is of 4130N tubing and may be repaired in conventional ways in accor-</p><p>dance with AC 43.13-1A/2A. All fittings are also of 4130N material. The repaired area should be</p><p>sanded and burned paint should be removed to a point where it can be feather edged by sanding.</p><p>A good etching solution would be a mixture of 1/2 fluid oz. of concentrated phosphoric acid in</p><p>one gallon of isopropanol (isopropal alcohol). If relative humidity is extremely low, add 1/4 cup of</p><p>distilled water to the solution. Factory paint is Air Ag yellow epoxy which does not require a</p><p>primer.</p><p>WINDSHIELD</p><p>Since the windshield is plexiglass, be careful to always use a clean rag and plastic wind-</p><p>shield cleaner to prevent scratches. If a crack is found near one of the attaching screws, stop-drill</p><p>with a no. 30 drill bit. The plexiglass windshield may be repaired or polished in accordance with</p><p>AC 43.13-1A.</p><p>If the windshield is replaced, file the sawed edges until a good fit is obtained. The bottom</p><p>edge of the windshield is on a 45o angle where it rests on top of the top fuselage skin. A felt strip</p><p>is used around the windshield edges. This felt is 1/16 x 2 with PSA backing and is p/n F-7. The</p><p>windshield is sealed around the upper and lower edge under the fiberglass flanges with zinc</p><p>Air Tractor, Inc. Maintenance Page 29</p><p>AT-401 April 1, 1998</p><p>Maintenance Page 30 Air Tractor, Inc.</p><p>July 13, 2011 AT-401</p><p>chromate putty. Then the entire perimeter of the windshield is sealed with PR-1422 A2 (See “Fuel</p><p>Tanks” for mixing instructions). Drill .166 holes through the windshield to match the aluminum</p><p>attachments. Then remove the windshield and enlarge the holes in the windshield to 3/16" to</p><p>prevent attach screws from over-stressing and cracking the windshield at any location.</p><p>The optional 3-Piece windshield is described below.</p><p>The safety glass center windshield can be cleaned with a soft rag and any good glass cleaner.</p><p>The windshield is sealed around the upper and lower edge under the metal flanges with</p><p>commercial grade putty. Then the entire perimeter of the windshield is sealed with PR1422-A2*</p><p>(see "Fuel Tanks" for mixing instructions). Drill .166 holes through the windshield to match the</p><p>aluminum attachments. Then remove the windshield and enlarge the holes in the windshield to</p><p>3/16" to prevent the attach screws from over-stressing and cracking the windshield at any</p><p>location.</p><p>*Alternate Sealer is PKMMC236A1/2</p><p>CANOPY DOORS</p><p>The canopy doors seal against the door frame with 3/8 x 1/2 p/n SC-41 neoprene sponge.</p><p>This material has a PSA backing but it is best to apply 3-M 8001 adhesive to the door frame in</p><p>order to get better adhesion. Be careful not to stretch the neoprene sponge during installation or it</p><p>will come loose.</p><p>The doors have a slight inward bow of 1/8" to allow for door deflection outward at high</p><p>speeds. The low pressure around the canopy causes the doors to bow outward. The door latch</p><p>should provide a snug door fit, and if it does not, and the weatherstrip is in good condition, bend</p><p>the latch arm that rides on the plated striker plate (p/n 10354-1 [L/H] or -2 [R/H]).</p><p>The door glass is p/n 10211-1 and is attached with 1/16 x 1 1/4 felt with PSA backing (p/n</p><p>F-7) around the perimeter. The machine screws around the glass are AN526-632-8 and the nuts</p><p>are AN365-632. Be careful not to over-tighten the screws or the glass will crack.</p><p>SEAT</p><p>The seat is attached to the seat rails with two C4-13R-303 Faspins. Do not raise the seat</p><p>above factory installed position but a tall person may want to lower the seat some. This is done by</p><p>lowering the seat to the desired position and drilling the set rails 15/64 and then reaming 1/4" for</p><p>the faspin installation. Make sure the lowered position clears the push-rod from the control stick.</p><p>The seat covers wear and need changing from time to time. The back cover is p/n 10541-1</p><p>and the bottom cover is p/n 10540-1. If the crotch strap is installed through the bottom seat</p><p>cover (used with AmSafe Airbag System), use bottom cover p/n 10540-3. Tools are available from</p><p>the factory to make seat cover replacement easier.</p><p>HOPPER</p><p>The hopper is made of Derakane and is heat-cured for greater chemical resistance. However,</p><p>it is not good practice to leave chemicals in the hopper overnight if it is known that these</p><p>chemicals have an adverse affect on fiberglass hoppers.</p><p>The hopper brace and the hopper window is sealed on installation with silicone sealer which</p><p>is impervious to most chemicals. The hopper is attached to the fuselage frame with AN6C23A (4</p><p>ea.) and AN6C11A (6 ea.) bolts and MS21044-C6 nuts (10 ea.). To remove the hopper it is</p><p>necessary to remove these 10 bolts, the screws and nuts on the firewall and aft end, the vent tube</p><p>connection inside the fuselage, and the hopper gate box and plumbing and the windshield.</p><p>HOPPER GATE BOX</p><p>The gate box is Transland 25559 and a set of gate box gaskets is used on each side of the</p><p>fiberglass enclosure skin when the gate box is installed. Since these gaskets are usually ruined</p><p>when the gate box is removed, new ones should be used when the gate box is re-installed. The</p><p>gaskets used are 60725 (4 ea.), 60227 (4 ea.). silicone sealer is used only on the corners of the</p><p>gaskets. The hopper door seal is a Transland 60713.</p><p>HOPPER LID</p><p>The hopper lid is of fiberglass and is sealed with strips of medium density nitrile 3/8 x 1.0.</p><p>The lid will not leak if the nitrile is in good condition and the latch assembly is adjusted to</p><p>tension the lid solidly against the hopper flange. The nitrile is not expensive and should be</p><p>changed as often as required during the spray season.</p><p>GATE BOX CONTROLS</p><p>The long push-rod assembly attached to the over-center controls of the gate box is p/n</p><p>80172-2 and has a MS14104-4 bearing in the aft end and a Bunting P26-8 bronze bushing in</p><p>the forward end. The aft end connects to the p/n 80067-10 torque tube assembly which is</p><p>supported on the fuselage lower longerons with two Fafnir PB 1/2 bearings attached with AN6-7A</p><p>bolts.</p><p>The boot attached to the lower fuselage skin is p/n 80133-1 with a p/n 70140-1 boot ring</p><p>and 90013-4 screws, MS21044C08 nuts. A p/n 80063-1 push-rod connects the lower torque</p><p>tube to the hopper handle in the cockpit. This push-rod has an adjustable Fafnir RE4M6 bearing</p><p>on the lower end, and a Fafnir RE4H6 bearing in the other end. The hopper handle (p/n 80066-1)</p><p>is supported on each end with Fafnir PB 1/2 bearings. Bolts through the bearings are AN6-15A.</p><p>During annual inspections, be sure the lower gate torque tube arm is positioned so as not to</p><p>chafe the boot or boot ring in the lower fuselage skin.</p><p>The micro - calibrator is a Transland p/n 20875 supported on the aft end with a p/n</p><p>Air Tractor, Inc. Maintenance Page 31</p><p>AT-401 April 1, 1998</p><p>80081-1 support assy and p/n 80104-1 shim, and supported on the forward end with a p/n</p><p>80080-1 support assy and a p/n 80106-1 clamp half.</p><p>SPRAY LEVER CONTROLS</p><p>The p/n 80073-1 spray lever assembly is attached to the aft cockpit wall and has a AG-235</p><p>Micro-control attached to limit the lever travel and hence the spray pressure. Keep the threaded</p><p>screw on the Micro-control greased and make sure the tab on the spray lever contacts only the</p><p>head of the AN4-5A bolt that is attached to the lower adjustment block.</p><p>The push-rod from the spray lever is p/n 80063-2 and has an adjustable Fafnir RE4M6</p><p>bearing in the lower end and a Fafnir RE4H6 bearing in the upper end.</p><p>The lower bellcrank is attached to the fuselage frame with a AN4-25A bolt. The bellcrank</p><p>has two Fafnir KP6A bearings with a p/n 70091-2 spacer bushing that allows the bolt to be fully</p><p>torqued. The bellcrank is p/n 80068-1 and has a p/n 80132-1 boot, 70140-1 boot ring attached</p><p>to the lower fuselage skin with 90013-4 screws, MS21044CO8 nuts.</p><p>The push-rod from the bellcrank to the valve is p/n 80065-1 which has a MS14104-4</p><p>bearing in each end.</p><p>SPRAY PUMP</p><p>The spray pump is an Agrinautics p/n 65219 attached to an Agrinautic p/n 60130 strut</p><p>assembly with AN5-13A bolts.</p><p>The standard fan is the Micronair p/n AT-4300 which is used for low to moderate spray</p><p>volume. For high volume applications, install a Weath-Aero adjustable pitch fan. Add 40 nozzles</p><p>to spray booms and change the tips on the spray nozzles to QU-4025. See page 10 of the</p><p>“Description Section” for more information on this subject.</p><p>SPRAY PLUMBING</p><p>The plumbing from the hopper gate box to the spray pump consists of a p/n 80385-1 tube</p><p>assembly with a p/n 22899 coupler attached to the gate box and a 80376-1 hose attached to the</p><p>80385-1 tube. The hose is clamped with 200-56S clamps which are entirely stainless.</p><p>The plumbing from the discharge side of the pump to the valve is p/n 81219-1 and has a</p><p>Transland 42320 coupler at each end. The hoses are p/n 80045-1 and are double clamped with</p><p>QS200M36S clamps. See drawing 80187 for complete details of the pump installation.</p><p>The tube attaching to the strainer is p/n 80047-2 and the boom “Tee” assembly is p/n</p><p>80392-10. Standard spray booms are p/n 80307-1 and will fit on either side. Micronair booms</p><p>are p/n 80333-1 (L/H) and 80333-2 (R/H).</p><p>The boom “Tee” assembly is supported on the L/H side with a p/n 80400-4 assembly and</p><p>on the R/H side with a p/n 80386-4 assembly. The straps on the support assemblies are p/n</p><p>80383-1 and are attached with AN4C6A bolts. D4-10T-303 Faspins are used to attach the</p><p>support assemblies to the fuselage frame. The installation is detailed on Drawing 80024 sheet 1.</p><p>Maintenance Page 32 Air Tractor, Inc.</p><p>April 1, 1998 AT-401</p><p>BOTTOM LOAD PLUMBING</p><p>The bottom load valve is a Transland 22395 which has shims that can be removed when</p><p>wear develops.</p><p>The aft half of the bottom loading plumbing is p/n 80328-1 and attaches to the bottom</p><p>loading valve with a 80045-1 hose and to the control valve with an 80046-1 hose and two</p><p>QS200M28S clamps.</p><p>The forward half of the bottom loading plumbing is a 80239-1 tube assembly.</p><p>The valve handle should be positioned straight back when the valve is closed. The valve is</p><p>attached to the L/H support assembly with four AN4-4A bolts. A transland 85053 adapter is</p><p>attached to the bottom load valve. The installation is shown in detail on drawing 80054.</p><p>SPRAY NOZZLES</p><p>Forty spray nozzles are standard. These are Spraying Systems Inc. p/n 4666 diaphram</p><p>check valve, 1/8 QJJ-V1 Quick Coupling body, and p/n QU-4010 spray tip. The aircraft is</p><p>equipped at the factory with 4010 tips which is for medium volume applications. For high volume</p><p>spraying QU4025 tips should be installed and if necessary an additional 40 nozzles should be</p><p>installed. Remove the p/n 3151 x 2 plugs and install p/n 3325 x 2 hex nipples for the extra</p><p>nozzles. Be sure to apply 3H permatex or equivilant to the threads of the hex nipples during</p><p>installation. For the best pattern the nozzles should be evenly spaced and the tips pointed back</p><p>and 10o down.</p><p>Air Tractor, Inc. Maintenance Page 33</p><p>AT-401 April 1, 1998</p><p>STRIPPING AND RE-PAINTING PARTS</p><p>1. The paint stripper most effective on urethane paint is Turco #5351.</p><p>2. The stripper is either sprayed on with a barrel pump or applied on small parts with a large</p><p>paint brush. If sprayed on be sure to consider wing direction so that over-spray will not damage</p><p>surrounding vehicles or aircraft.</p><p>3. When applying stripper, wear protective clothing and safety goggles.</p><p>4. Apply a medium to heavy coat of stripper. Temperature should be 50˚ F or warmer for best</p><p>results. Allow stripper to react with paint and remove with special brush having stiff bristles that</p><p>will not soften with stripper.</p><p>5. Spray on a second light coat of stripper as necessary and remove remaining paint with brush.</p><p>6. Rinse thoroughly with (approx. 150˚ F) water under pressure. Be sure entire film of stripper is</p><p>removed.</p><p>7. Apply Acid Etch with Scotch Brite pads and scrub metal surfaces thoroughly. Rinse with cold</p><p>water.</p><p>8. Before the part is dry, apply generous amounts of Alodine with a clean white rag. The Alodine</p><p>should act within two or three minutes and when rinsed off with cold water should leave a very</p><p>light gold surface. Do not leave the Alodine too long or allow it to dry as a dark brown film will</p><p>result which is undesirable and should be removed and the part reprocessed.</p><p>9. When the part is completely dry, apply a coat of High Solids Epoxy Primer:</p><p>9.1 Mixing ratio is 4 parts Pigmented Component and 1 part Adduct. Always follow</p><p>manufacturer recommended mixing ratios.</p><p>9.2 Surfaces must be clean and free of grease, dirt, oil, rust, fingerprints, and other</p><p>contaminants to insure optimum adhesion and performance properties. Parts may be</p><p>cleaned using an alcohol soaked soft rag.</p><p>9.3 Apply primer using conventional spray equipment or HVLP spray equipment.</p><p>9.4 Ideal coating thickness is 0.5 mils dry.</p><p>9.5 Spray coatings with smooth, even strokes. Runs and sags are to be avoided.</p><p>9.6 Application temperature should be between 65˚-100˚ F.</p><p>Maintenance Page 34 Air Tractor, Inc.</p><p>April 20, 2005 AT-401</p><p>Air Tractor, Inc. Maintenance Page 35</p><p>AT-401 July 13, 2011</p><p>9.7 Epoxy primer should be allowed to flash before recoating with epoxy primer.</p><p>9.8 Air dry time to topcoat at 77˚-100˚ F Pis 2 hours minimum.</p><p>9.9 Full cure is achieved after approximately 18 hours of air dry.</p><p>9.10 If parts are allowed to dry in excess of 48 hours before topcoat application, they must be</p><p>sanded and reprimed.</p><p>10.Apply Urethane Topcoat on Primed Parts:</p><p>10.1 Mixing ratio is 2 parts base component, 1 part hardener, and 1 part activator. Always</p><p>follow manufacturer recommended mixing ratios.</p><p>10.2 Surfaces must be clean and free of grease, dirt, oil, rust, fingerprints, and other</p><p>contaminants to insure optimum adhesion and performance properties. Parts may be</p><p>cleaned using an alcohol soaked lint-free cotton cloth.</p><p>10.3 Parts should be wiped with a urethane grade tack cloth and then air blown to remove</p><p>any foreign materials.</p><p>10.4 Mix topcoat in accordance with manufacturer instructions. Do not deviate from</p><p>manufacturer recommended mixing ratios.</p><p>10.5 The paint booth temperature should be maintained between 65˚-100˚ F. Ideal booth</p><p>conditions are 75˚-85˚ F and a relative humidity of 45%.</p><p>10.6 Apply topcoat using conventional spray equipment or HVLP spray equipment.</p><p>10.7 Ideal coating thickness is 2.8-3.5 mils dry.</p><p>10.8 Spray coatings with smooth, even strokes. Runs and sags are to be avoided.</p><p>10.9 Cure time is 4.5 hours to tape at 120˚F, or 6-8 hours to tape at 77˚ F.</p><p>10.10 Clean equipment using Ketone (MEK) solvent. Do not allow material to cure inside</p><p>spray equipment.</p><p>Priming Aluminum Parts with Chromated Alkyd Primer</p><p>Parts that do not receive a finish coat of paint (such as wing ribs) are primed with Chromated</p><p>Alkyd Primer conforming to spec TT-P-1757B, Type I, Class C. Surfaces must be clean and free of</p><p>grease, dirt, oil, rust, fingerprints, and other contaminants to insure optimum adhesion and</p><p>performance properties. Parts may be cleaned using an alcohol soaked soft rag. Follow the Acid</p><p>Etch and Alodine process described in the "Stripping and Re-painting Aluminum Parts" section</p><p>Maintenance Page 35A Air Tractor, Inc.</p><p>July 13, 2011 AT-401</p><p>above. Apply a light coat of Chromated Alkyd Primer thinned with Toluene R2K1 or Xylene R2K4 if</p><p>necessary to achieve proper viscosity. Spray coatings with smooth, even strokes. Runs and sags</p><p>are to be avoided. The primer application should be a thin film.</p><p>Stripping and Repainting Steel Parts</p><p>Steel parts are to be cleaned of all oils and then sand-blasted. If sand-blasting is not available,</p><p>clean the part thoroughly, wipe dry, sand, and etch with a mixture of 1.0 gal. Isopropyl Alcohol</p><p>and 1/2 fluid oz. of concentrated Phosphoric acid. If applying finish coat over bare metal, prime</p><p>first with High Solids Epoxy Primer (see instructions above) and paint using Urethane Topcoat</p><p>process (see instructions above).</p><p>Materials Used for Stripping, Painting, and Preservation</p><p>Urethane Topcoat Materials</p><p>Part No. (Sherwin Williams) Description Amount used per A/C</p><p>CM0840405 Yellow finish coat 10 gal.</p><p>Z05265 Black finish coat 1 / 2 gal.</p><p>Z05266 Blue finish coat 1 / 2 gal.</p><p>CM0840081 Hardener 5 gal.</p><p>CM0840A05 Activator (60-70° F) 5 gal.</p><p>CM0110093 (slow) or CM0110944 Urethane Reducer 3 gal.</p><p>CM0483928 Primer-Pigmented Component 4 gal.</p><p>CM0120828 Standard Epoxy Adduct 1 gal.</p><p>CM0110944 Primer Reducer 2 gal.</p><p>Chromated Alkyd Primer Materials</p><p>Part No. Description Amount used per A/C</p><p>TT-P-1757B Yellow zinc chromate primer 5 gal.</p><p>T1-548C Toluene (R2K1) 5 gal.</p><p>Air Tractor, Inc. Maintenance Page 35B</p><p>AT-401 April 20, 2005</p><p>Surface Preparation Materials</p><p>Part No Description Amount used per A/C</p><p>Turco #53351 Stripper 10 gal.</p><p>Acid Etch 3 gal.</p><p>Alodine 2 lbs.</p><p>Isopropyl Akcohol 2 gal.</p><p>Phosoporic Acid 1 fluid oz.</p><p>Internal Oiling Steel Parts</p><p>Part No. Description Amoont used per A/C</p><p>Linseed Oil 1 gal.</p><p>Maintenance Page 36 Air Tractor, Inc.</p><p>AT-401 April 1, 1998</p><p>TORQUE VALUES FOR SHOP USE</p><p>Torque Value (inch-pounds)</p><p>Size of Nut or Bolt Tension Type Nuts Shear Type Nuts</p><p>1032 60-70 20-25</p><p>1/4-28 100-120 30-40</p><p>5/16-24 200-240 60-85</p><p>3/8-24 300-330 95-110</p><p>7/16-20 550-600 270-300</p><p>1/2-20 800-900 290-410</p><p>9/16-18 1,100-1,300 480-600</p><p>5/8-18 1,700-1,900 660-780</p><p>3/4-16 2,800-3,000 1,300-1,500</p><p>7/8-14 3,500-4,000 1,500-1,800</p><p>1-14 6,000-6,400 2,200-3,300</p><p>NOTE:</p><p>1. The chart applies to all standard or high strength aircrat alloy steel bolts.</p><p>2. The lower value is used when the bolt is held stationary and torque applied to the nut. For</p><p>the revese of ths procedure use the upper value.</p><p>3. Tension type nuts are AN365, AN363, AN310.</p><p>4. Shear type nuts are AN364, AN320.</p><p>ELECTRICAL SYSTEM TROUBLE SHOOTING</p><p>No Power:</p><p>If the battery switch is on, but there is no power, first be sure that the battery is charged</p><p>and all circuit breakers have been checked. Check the cables on the battery for looseness and the</p><p>battery ground connection. If there is still no power, check the battery switch and the switch</p><p>circuit. If all is in order, the only step left is to replace the master relay which is mounted on the</p><p>battery platform. This is a Cutler Hammer p/n 6041H202A which has been sealed against</p><p>chemical entry and is Air Tractor p/n 60045-2. Alternate relay is the Kissling p/n 29.314.12.903</p><p>which is sealed.</p><p>Starter will not engage:</p><p>If there is power with the battery switch on but the starter will not engage, check the starter</p><p>switch and circuit. Check the starter relay on the firewall. This is the same as the master relay</p><p>except for different sealing which makes it an Air Tractor p/n 60045-1 or the Kissling relay above.</p><p>If the relay works and the other checks are OK, then there is something wrong with the starter,</p><p>providing the ground wire to the oil tank bushing is secure.</p><p>Air Tractor, Inc. Maintenance Page 37</p><p>AT-401 April 1,1998</p><p>No rise in voltage showing on voltmeter equipped aircraft:</p><p>Since later aircraft have a voltmeter installed instead of an ammeter, compare the voltage</p><p>shown on the voltmeter with the voltage measured at the battery.</p><p>Alternator overcharging:</p><p>If the alternator is charging too many volts on voltmeter, check the voltage with engine</p><p>running at 2000 RPM. If voltage is more than 28.5 volts re-set voltage in alternator contols with</p><p>adjustment screw.</p><p>Skytronic Alternators:</p><p>Each Air Tractor equipped with Skytronic alternator has a set of instructions from Skytron-</p><p>ics included in the delivery kit. If a problem develops, consult these instructions.</p><p>LIGHTING SYSTEM TROUBLE SHOOTING</p><p>Electronic Instrument Light Dimmer</p><p>Description</p><p>The instrument lights are dimmed by two separate dimmer controls. One of these is for the upper</p><p>panel instrument lights and the other is for the lower panel lights. The instrument light switch</p><p>feeds power to the dimmer circuits and the flap light through the five Amp instrument-light</p><p>circuit breaker. The pilot has control of the instrument light intensity through the knob on the</p><p>variable resistor, P/N RV4NAYSD-102A, mounted in the upper panel. There is a separate</p><p>control for each</p><p>of the upper panel and the lower panel lights. The controls for the upper and</p><p>lower panels are identical except for wire numbers. The variable resistor controls the bias on the</p><p>base pin of the P/N 2N3055 power transistor. Power is fed to the collector of the transistor while</p><p>the emitter of the transistor outputs current to the lighting bus. The schematic of the dimmer</p><p>circuit is shown on drawing 60059 page 1, and the assembly details are shown on drawing</p><p>60647.</p><p>Trouble Shooting</p><p>The following instructions are for the upper panel dimmer circuit. Trouble shooting the lower</p><p>panel is identical except that on later aircraft the wires are numbered differently from the upper</p><p>panel control to the lower panel control. Use the schematic, drawing 60059 pg 1, and the</p><p>assembly drawing, 60647, to aid in trouble shooting.</p><p>If one of the electronic dimmers should fail to operate, first check the five-Amp-instrument-light</p><p>circuit breaker. If the flap light burns when the master switch and the instrument light switches</p><p>are activated, the circuit breaker and switch are good. Open the lower panel and visually inspect</p><p>Maintenance Page 38 Air Tractor, Inc.</p><p>April 1, 1998 AT- 401</p><p>the wiring harness for broken wires and corroded or bad connections.</p><p>To check for a short in the instrument light fixtures, make sure the master switch is OFF and</p><p>disconnect the 60011-151 transistor output wire from the lighting bus. Fabricate a test lead</p><p>with a five-Amp circuit breaker, two alligator clips, and about 18 inches of 20-gauge wire. Make</p><p>sure that the instrument lights work by connecting the test lead, with the circuit breaker in line,</p><p>between the power bus and the lighting bus. Turn ON the master switch. If the lights illuminate,</p><p>the fixtures and wiring are fine. If the circuit breaker in the test lead pops, there is a short in the</p><p>instrument light fixtures or wiring. If there is a short, isolate it and make the necessary repairs.</p><p>Make sure all of the lights and wiring of the system are working before proceeding, since shorts</p><p>are the most common cause of transistor failure.</p><p>Once it is known that the instrument lights and wiring are good, and the dimmer still will not</p><p>control them, use a Volt meter to make sure that the instrument-light switch is feeding bus</p><p>voltage to the variable resistor and the “C” terminal of the transistor. To access the terminals of</p><p>the transistor, remove the two screws that hold the heat sink to the lower panel. The variable-</p><p>resistor terminal with the 60011-437 wire is the power wire from the instrument light switch. If</p><p>voltage is not present at either one or both of these terminals, isolate the trouble and make the</p><p>necessary repairs to the wiring. Use the Volt meter to check the voltage at the “B” terminal of the</p><p>transistor. This voltage should vary from 0 to bus level when the control knob is turned. If the</p><p>voltage is not proper at the “B” terminal, remove the transistor and recheck the voltage at the “B”</p><p>terminal of the transistor socket. To remove the transistor from the socket, remove the two</p><p>screws holding it to the heat sink. Pull the transistor out of the socket. If the voltage is still not</p><p>proper at the “B” terminal, the variable resistor (P/N RV4NAYSD-102A) is bad or has a bad</p><p>ground. If the voltages to the”B” and “C” terminals of the transistor are good and the dimmer</p><p>does not work, the transistor is bad. To install a new transistor (P/N 2N3055), coat the bottom of</p><p>the transistor with a thin coat of heat-sink compound. Insert the mica insulator over the two</p><p>transistor leads and stick it to the heat-sink compound. Coat the bottom of the mica insulator</p><p>with a thin coat of heat sink compound. White heat-sink compound can be obtained at most</p><p>Radio Shack or electronic supply stores. Most Radio Shack stores also stock the 2N3055</p><p>transistor. Plug the transistor through the heat sink and into the socket. Install the screws that</p><p>were removed. Make sure that the shoulders of the transistor-socket-screw holes seat properly in</p><p>the heat-sink holes. The case of the transistor is one of the electrical connections of the</p><p>transistor, and must not be grounded to the heat sink or the aircraft. If the case is shorted to</p><p>ground, with the power on, the transistor will be ruined. Once the wires have been reconnected</p><p>and the unit is working properly, mount the heat sink to the lower panel and secure any loose</p><p>wires as necessary. Double check the operation of the unit before fastening the lower panel and</p><p>returning the aircraft to service.</p><p>CHECKING THE BATTERIES</p><p>The batteries are checked by determining the level of the electrolyte in each cell. First, the</p><p>battery caps are removed. Then each cell is inspected individually. Using a light if necessary, the</p><p>electrolyte level should be observed at or slightly above the plastic split-ring that is visible</p><p>Air Tractor, Inc. Maintenance Page 39</p><p>AT-401 April 1, 1998</p><p>through the filling hole.</p><p>If the electrolyte fluid level is low and adding fluid is necessary, the electrolyte level can be</p><p>raised by adding distilled water. The battery should not be overfilled. The electrolyte level should</p><p>not be more than one-quarter inch above the split ring.</p><p>When a battery seems weak or will not hold a charge after charging, replacing the battery</p><p>may be necessary. The charge capacity of individual cells may be determined by checking the</p><p>specific-gravity of the electrolyte in those cells.</p><p>The specific-gravity check can be done with the use of a hydrometer constructed of acid-</p><p>resistant materials. The specific-gravity should range from 1.1 for a fully-discharged cell to 1.3</p><p>for a fully-charged cell. A variance of specific gravity more than 0.1 from other cells in the battery</p><p>is an indication of a weak cell and the battery should be replaced.</p><p>Commercial battery hydrometers are normally used for specific-gravity checks. These hy-</p><p>drometers may display specific-gravity readings or might have red and green bands. Depending</p><p>on the state of charge, the specific-gravity readings should not be interpreted as absolute but as</p><p>comparative readings with other cells in the battery. A single cell whose specific-gravity reading</p><p>is at wide variances with other cells in the battery suggests a dead cell requiring replacement of</p><p>the battery.</p><p>ELECTRICAL SYSTEM DESCRIPTION</p><p>Voltmeter</p><p>The wiring schematic for the Voltmeter is shown in Drawing 60001. The Voltmeter shows the</p><p>voltage on the airplane’s electrical bus. Voltmeter readings may be used to determine the condition</p><p>of the battery and Starter/Generator.</p><p>When the Master Switch is “ON”, with the Starter/Generator not charging, with no load on the</p><p>system, the fully-charged battery voltage should be between 23 and 24 volts. When the Starter/</p><p>Generator is charging, the voltage on the airplane bus should be approximately 28 volts.</p><p>Fuel Gauging</p><p>The wiring schematic for the fuel gauging system is shown in Drawing 60198. The fuel quantity</p><p>is shown on the panel-mounted fuel gauge. Each of the wing fuel cells is gauged separately. The fuel</p><p>quantity in each of the fuel tanks is displayed on the panel fuel gauges.</p><p>The panel-mounted fuel gauge is a micro-ammeter with a full-scale range of 100 micro-amps.</p><p>A circuit board is attached to the binding posts of the instrument. Circuitry on this board provides</p><p>a 4.3 -volt power supply for the fuel-gauging system. This board also has a trimmer-potentiometer.</p><p>This trimmer is used to calibrate the full-scale readings on the micro-ammeter.</p><p>The sender is grounded through its mounting bolts.</p><p>Wing Flaps</p><p>The wiring schematic for the wing flaps is shown in Drawing 60198. Power to drive the flaps up</p><p>and down is provided by the cockpit flap switch. The wiring from the flap switch is routed through the</p><p>micro-switches that serve as limit switches for the full "ON" and full "DOWN" positions.</p><p>Stall-Warning Horn</p><p>The wiring schematic for the stall-warning horn is shown in Drawing 60198. The horn is</p><p>connected in series with the lift-detector switch that is located near</p><p>the leading edge of at mid-span</p><p>of the right-hand wing.</p><p>The lift-detector switch is controlled by a tab that projects forward into the prevailing airstream.</p><p>When at rest, the weight of the tab holds it down, opening the switch. When the airflow around the</p><p>lift detector shifts to a forward direction, the tab is lifted, closing the switch and causing the horn to</p><p>sound.</p><p>Night Working Lights</p><p>The wiring schematic for the night working lights is shown in Drawing 60276. The Night Working</p><p>Lights combine the functions of the 600-watt landing lights and the 450-watt turn lights for optimum</p><p>visibility while operating at night.</p><p>The extension of the landing lights is individually controlled by the extend-and-retract switches</p><p>located on the lower switch panel. These switches allow the landing lights to be stopped at any point</p><p>in their extension or retraction to provide the best placement of lighting to suit the pilot. The landing</p><p>lights can be turned “ON” or “OFF” by use of the “MAIN” switch to the right of the extend-and-retract</p><p>switches on the lower panel.</p><p>The turn-light switch is a push-on, push-off button switch located at the upper left of the control</p><p>stick. When the landing-light main switch is “ON” and the turn-light switch is turned on, the turn-</p><p>light selector switch atop the control stick is enabled. This switch has “LEFT”, “RIGHT”, and center</p><p>“OFF” positions. When the turn-light selector switch is moved out of its center position, left or right,</p><p>the wing-tip-mounted turn light is turned “ON” on the selected side while the landing lights are</p><p>simultaneously turned “OFF”. Return of the turn-light switch to its center position restores the</p><p>landing light to “ON” and the selected turn light to “OFF”.</p><p>All of the lamp filament circuits are switched by relays. Since the main landing lights are not</p><p>individually selected “ON”, a single relay switches both lamps simultaneously. This relay is activated</p><p>“ON” when the “MAIN” switch is “ON” and both of the double-pole, double-throw turn relays are in</p><p>their normally-closed positions. When the working light switch is “ON” and the turn-light selector</p><p>switch is moved from its center position, the coil of the selected turn relay is energized. This causes</p><p>the armature of the relay to move, turning the light ‘ON” and simultaneously breaking the circuit to</p><p>the relay coil that powers the main landing lights.</p><p>When the working-light switch is “OFF”, movement of the turn-light selector switch has no effect.</p><p>Windshield Washer</p><p>The wiring schematic for the windshield washer is shown in Drawing 60118. When the switch</p><p>is closed, the pump’s motor starts and the solenoid valve is opened. The flow of windshield-washing</p><p>fluid will continue until the switch is released. The purpose of the solenoid is to provide a sharp cutoff</p><p>of fluid when the switch is released. This prevents the dribbling of fluid onto the windshield.</p><p>Maintenance Page 40 Air Tractor, Inc.</p><p>April 1, 1998 AT-401</p><p>Air Tractor, Inc Maintenance Page 41</p><p>April 20, 2005 AT-401</p><p>Windshield Wiper</p><p>The wiring schematic for the optional windshield wiper is shown in Drawing 60737. The wiper</p><p>switch has three positions, “HIGH”, “LOW”, and “PARK”. When the switch is in the “PARK” position,</p><p>the wiper blades are parked and the power to the wiper motor is off.</p><p>Cockpit Lighting</p><p>The wiring schematic for the cockpit lights is shown in Drawing 60059 p1. The intensity level</p><p>of the cockpit lights, except for the dome and map lights, is controlled by the solid-state dimming</p><p>circuit.</p><p>When the panel light switch is turned “ON”, power is available to the dimming circuit. The panel-</p><p>light intensity is controlled by the panel-light rheostat on the instrument panel.</p><p>Flap Light</p><p>The wiring schematic for the flap light is shown in Drawing 60059. The flap light is located in</p><p>a housing on the upper side of the left-hand wing just forward of the wing flap, near the center of the</p><p>span of the flap. The light illuminates marks on the leading edge of the flap, providing an indication</p><p>of the amount of deflection of the flap. The flap light is controlled by the instrument-light switch, but</p><p>it is not dimmed by the panel-light dimming circuitry.</p><p>Position and Strobe Lighting</p><p>The wiring schematic for the position lights and the strobe lights is shown in Drawing 60059.</p><p>These lights are controlled by the navigation-light switch on the lower instrument panel. When the</p><p>switch is placed in the “DOWN” position, power is sent to the red light on the left-hand wing tip, the</p><p>green light on the right-hand wing tip, and the white light on the rudder. When the switch is placed</p><p>in the “UP” position, power is sent to the three position lights plus the strobe lights located on each</p><p>wing tip.</p><p>AIRSPEED SYSTEM</p><p>Should irregular airspeed readings occur, there is the possibility that water has entered</p><p>the static or pitot lines. To drain the lines, there are three locations where the lines may be</p><p>broken at the fittings for draining.</p><p>1. At each static port on the upper fuselage deck the plugs on the lower side of the "Tee" may</p><p>be removed</p><p>2. The line from the static ports that goes forward to the cockpit may be broken under the</p><p>R/H lower aft corner of the door frame.</p><p>3. The pitot line may be broken in the lowest spot where it passes across the fuselage below</p><p>the main spar of the wing.</p><p>Maintenance Page 42 Air Tractor, Inc.</p><p>February 9, 2012 AT-401</p><p>AVIONICS</p><p>Optional radio equipment may include those listed in drawing 60616. Removal or</p><p>replacement of any of the radios requires removal of applicable fasteners in accordance with their</p><p>corresponding installation drawing as indicated on drawing 60616. All fasteners must be</p><p>routinely inspected for tightness. Antennas must be routinely inspected for secure attachment to</p><p>the aircraft and structural integrity. Routine cleaning of the avionics box and its components may</p><p>be done by wiping with a damp cloth. Ventilation openings in equipment housings should be</p><p>open and free from obstructing lint and dust. For further information on testing, adjustment,</p><p>troubleshooting and repairs of the electronic equipment and systems, refer to the manufacturer‟s</p><p>maintenance instructions, manuals and the applicable Federal Aviation Regulations. Additional</p><p>avionics maintenance information is found in FAA AC 43.13-1B Chapter 11, 12 and 15.</p><p>Electrical power to the radios is controlled by a circuit breaker switch located on the radio</p><p>box. Power is then distributed to each avionics component which is protected by an adequately</p><p>rated circuit breaker located on the radio box or in the lower panel. Wiring schematics specific to</p><p>each avionics component may be obtained from manufacturer‟s data. These schematics are found</p><p>in the figures section of the manual.</p><p>LIFE-LIMITED ITEMS</p><p>FAA Requirements:</p><p>The safe-life of Air Tractor Model AT 401 and AT-401B wing carry-through structure, and</p><p>attaching structure is 9,800 hours time in service for serial numbers -1183 and subsequent. For</p><p>earlier serial numbers, refer to FAA Airworthiness Directive 2006-08-08 R1.</p><p>If the AmSafe Airbag System is installed, the following are time-limited parts:</p><p>The EMA (Electronics Module Assembly) is to be removed and returned to AmSafe</p><p>Aviation for refurbishment after:</p><p>a period of seven (7) years calculated from the month of manufacture regard</p><p>less of storage or service time or combination of both.</p><p>The EMA can only be renewed by AmSafe Aviation.</p><p>In addition, the EMA is to be removed for disposal after:</p><p>a maximum storage period of fourteen (14) years calculated from the month of</p><p>manufacture, or;</p><p>upon expiration of the service life defined as the total sum of storage life and</p><p>installation life, which must not exceed fourteen (14) years calculated from the</p><p>month of manufacture.</p><p>The Inflator Assembly is to be removed and returned to AmSafe Aviation for disposal</p><p>after:</p><p>a maximum storage period of ten (10) years calculated from the month of</p><p>manufacture as indicated in the</p><p>expiration date stamped on the gas cylinder,</p><p>or;</p><p>upon expiration of the service life defined as the total sum of storage life and</p><p>installation life, which must not exceed ten (10) years calculated from the</p><p>month of manufacture as indicated in the expiration date stamped on the gas</p><p>cylinder.</p><p>Upon expiration of the service life (total life), the Inflator Assembly cannot be renewed.</p><p>Air Tractor, Inc. Maintenance Page 43</p><p>February 9, 2012 AT-401</p><p>Air Tractor Recommendations:</p><p>Air Tractor Service Letters are used to communicate field experience that may be helpful to</p><p>the owner of the airplane. Some of these service letters recommend the retirement of certain parts</p><p>after they have been in operation for a given period of time.</p><p>These Air Tractor Service Letters are listed below with an abbreviated explanation of the</p><p>action recommended:</p><p>Service Letter No. Recommended Action</p><p>104 Recommends replacement of main landing-gear springs at between 1500</p><p>hours and 4000 hours, depending on type of service. See Service Letter</p><p>for details.</p><p>117 Recommends replacement of landing-gear attaching bolts between 300</p><p>hours and 2000 hours, depending on type of service. See Service Letter</p><p>119 Recommends replacement of tail landing-gear springs at between 1000</p><p>hours and 2000 hours, depending on types of service. See Service Letter</p><p>for details.</p><p>TIE-DOWN INSTRUCTIONS</p><p>To help protect against damage from strong or gusty winds when parked, your Air Tractor</p><p>airplane should be tied down to ground tie-down facilities using lines made of nylon rope, vinyl-</p><p>covered chain or cable, or nylon webbing. The lines should have a tensile strength of more than</p><p>3,000 lbs.</p><p>The airplane should be parked with the nose pointed into the anticipated wind, if possible.</p><p>The parking brake should be set and the main landing gear tires should be chocked front and</p><p>rear. (CAUTION: Do not set the parking brake when the brakes are overheated or during</p><p>cold weather when accumulated moisture may freeze the brakes. The main wheels should</p><p>always be chocked when parked, but this is especially important if the parking brake is not</p><p>set.) Install the control stick lock and rudder lock and set all trim tabs to neutral position. If</p><p>available, install a pitot tube cover, engine inlet cover, engine exhaust covers (when cool), and</p><p>install the propeller tether.</p><p>Secure the wings to the ground anchors using the wing tie-down rings located beneath the</p><p>front spars of each wing, and secure to the ground anchors. These lines should be oriented as</p><p>close to vertical as possible (within 30 degrees of vertical). The tail wheel is secured by wrapping</p><p>and tying the tie-down line around the tailwheel spring. This line should be tied to a ground</p><p>anchor located slightly aft of the tail wheel. Use care to avoid damaging the tail wheel lock</p><p>mechanism.</p><p>If winds in excess of 20 mph from the rear of the aircraft are expected or possible, suitable</p><p>blocks should be used to lock the control surfaces (ailerons, elevators, and rudder) in place and</p><p>relieve strain on the control systems. Very large damaging dynamic loads are possible with a</p><p>gusty reverse flow of air over the control surfaces. Should this happen without blocks in place, be</p><p>sure to check all push-rods and rod-ends in the aileron control system for damage before flight.</p><p>Maintenance Page 44 Air Tractor, Inc.</p><p>February 9, 2012 AT-401</p><p>TOWING INSTRUCTIONS AND LIMITATIONS</p><p>The airplane must be towed with the use of an appropriate tow bar attached to the main</p><p>landing gear. The proper towing points are the sheet metal rings on the inner side of the landing</p><p>gear strut in the same plane as the axle. Towing with attachment to the tail-wheel spring is not</p><p>recommended. The tail-wheel lock should always be disengaged while the airplane is being towed.</p><p>A towing bar can be made from two 12-foot-long 4130 steel tubes and a three quarter-inch</p><p>steel bar. The tube's outside diameter should not be less than two inches and the wall thickness</p><p>should be at or above .065 inch.</p><p>The tubes are pinned together at one end with a loose 1/2 inch bolt and an attachment to</p><p>join to the towing lug or ball on a vehicle. The three-quarter-inch steel bar is bent at 90 degrees</p><p>with four inches of bar extending in one direction and three inches in the other direction from the</p><p>bend. These bent bars are welded to the free ends of the tubes. The three-inch leg is pointed</p><p>downward and the other is fillet-welded to the bottom of the tube. These downward-projecting</p><p>pintles fit loosely into the towing wings in the airplane's landing gear. A hole may be drilled</p><p>through the three-inch leg at a quarter-inch from its end for a spring pin, if desired.</p><p>The airplane can be pulled or pushed using the tow bar. If the airplane is towed into tight</p><p>quarters, a wing-walker should be engaged to avoid damage to wing tips and tail members where</p><p>visibility is limited.</p><p>The airplane should not be towed faster than 5 miles per hour on a smooth surface</p><p>without chug-holes or sharp bumps. Landing gear damage, particularly tail-wheel damage, can</p><p>result from dropping the gear into holes at high speeds.</p><p>AMSAFE AIRBAG SYSTEM</p><p>The AmSafe Airbag system consists of a lap belt and crotch strap attached to the seat</p><p>frame, a shoulder harness with integrated airbags, two compressed gas inflators, and an</p><p>electronics module and cabling. All maintenance on the system must be performed by an AmSafe</p><p>Authorized Service Center per AmSafe Aviation Document Number E510500.</p><p>The maintenance requirements of the system include an annual inspection and functional</p><p>test of the system. The electronics module must be returned to AmSafe for refurbishment after a</p><p>period of seven years from month of manufacture and must be taken out of service after a period</p><p>of 14 years from month of manufacture. The inflators must be removed and replaced after a</p><p>period of 10 years from the month of manufacture.</p><p>Any time any component of the AmSafe Airbag system is disconnected or removed from the</p><p>aircraft, the system requires a functional test performed by an AmSafe Authorized Service Center.</p><p>Air Tractor, Inc. Maintenance Page 45</p><p>February 9, 2012 AT-401</p><p>CHECKING THE BATTERIES</p><p>The batteries are checked by determining the level of the electrolyte in each cell. First, all</p><p>of the battery caps are removed. Then each cell is inspected individually. Using a light if</p><p>necessary, the electrolyte level should be at or slightly above the plastic split-ring that is visible</p><p>through the filling hole.</p><p>If the electrolyte fluid level is low and adding fluid is necessary, the electrolyte level can be</p><p>raised by adding distilled water. The battery should not be overfilled. The electrolyte level should</p><p>not be more than one-quarter inch above the split ring.</p><p>When a battery seems weak or will not hold a charge after charging, replacing that battery</p><p>may be necessary. The charge capacity of individual cells may be determined by checking the</p><p>specific gravity of the electrolyte in those cells.</p><p>The specific gravity check can be done with the use of a hydrometer constructed of acid-</p><p>resistant materials. The specific gravity should range from 1.1 for a fully-discharged cell to 1.3 for</p><p>a fully charged cell. A variance of specific gravity more than 0.1 from other cells in the battery is</p><p>an indication of a weak cell and the battery should be replaced.</p><p>Commercial battery hydrometers are normally used for specific gravity checks. These</p><p>hydrometers may display specific gravity readings or might have red and green bands. Depending</p><p>on the state of charge, the specific gravity readings should not be interpreted as absolute but as</p><p>comparative readings with other cells in the battery. A single cell whose specific gravity reading is</p><p>at</p><p>wide variances with other cells in the battery suggests a dead cell requiring replacement of the</p><p>battery.</p><p>LEVELING</p><p>The airplane is leveled to “level flight attitude” by jacking the tailwheel. See LIFTING AND</p><p>JACKING section of this manual. The airplane is in level flight attitude when the top (right next to</p><p>the side of the fuselage) of the L/H landing gear leg is level. Use an accurate bubble level, placed</p><p>at this location to determine when the aircraft is level. The airplane should be in this level</p><p>position for aircraft weighing and other maintenance/installation items that require the aircraft to</p><p>be in level flight attitude. Care should always be taken when the aircraft is lifted to prevent</p><p>damage to the aircraft or harm to people around it.</p><p>WEIGHT AND BALANCE</p><p>The proper maintenance of weight and balance records is important to ensure that the</p><p>airplane is operated within the weight and center of gravity limits that are established in the Flight</p><p>Manual. The airplane should be weighed in the attitude described in the LEVELING section of</p><p>this manual.</p><p>DAILY INSPECTIONS</p><p>Use the Preflight, Walk-Around Inspections called out in the Operations section of this</p><p>manual.</p><p>PERIODIC INSPECTIONS</p><p>The figures in parenthesis indicate approximate flying hours between inspections. A pro-</p><p>gressive inspection procedure is recommended, but the time between inspections should not</p><p>exceed those indicated below.</p><p>PROPELLER</p><p>1.* (100) Move blades to low pitch and check exposed portion of piston for corrison, galling</p><p>or nicks.</p><p>2.* (25) Examine all exterior parts of propeller blades for corrosion, bends, nicks, etc.</p><p>Examine entire leading edge, trailing edge and tip portions of blades for develop-</p><p>ment of cracks.</p><p>3.* (100) Check piston tightness. Correct torque is 720 pound-feet.</p><p>4.* (100) Check security of counterweight bearing and shaft installation. Check clearance</p><p>between counterweight bracket and bronze thrust washer. Minimum clearance</p><p>should be .003 to .006 inch.</p><p>*For12D40 propellers only.</p><p>ENGINE AND MOUNT</p><p>1. (25) Inspect speed ring Attach Straps (See Service Letter #113).</p><p>2. (100) Check for loose nuts and broken lock wire.</p><p>3. (100) Inspect exhaust system for cracks and signs of burning.</p><p>4. (100) Inspect all control linkages for security and correct travel. Remove excessive play</p><p>by adjusting the threaded sections of each control rod.</p><p>5. (100) Check accessories for security. Check tightness of cylinder hold-down nuts and</p><p>push-rod cover nuts.</p><p>6. (100) Inspect cylinders for leaks at barrel to head connection and for cracks around</p><p>spark plug bushings. Inspect inter-cylinder drain hoses.</p><p>7. (100) Inspect engine vibration isolators for cracks, swelling, or separation of elastomer.</p><p>8. Annual Check torque on mount bolts at fuselage (1,100 inch-pounds).</p><p>9. Annual Inspect all welds at engine mount clusters. Inspect vibration isolators for condi-</p><p>tion and security of clamp.</p><p>10. Annual Check torque on bolts through vibration isolators (300 inch-pounds on nut).</p><p>ELECTRICAL SYSTEM</p><p>1. (50) Check battery for condition, charge, and water level. Check battery vent lines and</p><p>tubes for clogging.</p><p>2. (50) Inspect wires around battery and along fuselage tubes for chafing or loose con-</p><p>nections.</p><p>Air Tractor, Inc. Inspection Page 1</p><p>AT-401 March 30, 2003</p><p>3. (50) Inspect relays and other electrical components in vicinity of battery and on fire-</p><p>wall for loose connections, signs of short, etc.</p><p>4. (100) Inspect starter and alternator connection to engine, and wiring to terminals.</p><p>5. (100) Remove R/H side skin below hopper and check wire bundle for security and</p><p>chafing at firewall.</p><p>6. (100) Inspect under instrument panel for loose wires or chafing, or evidence of shorting.</p><p>(It may be necessary to remove control stick for comfort.)</p><p>FUEL SYSTEM</p><p>1. (100) Remove and clean fuel strainer in carburetor. Check fuel pump seals by watching</p><p>overboard drain during run-up.</p><p>2. (100) Check the wobble pump for leaks (See page 16 Maintenance Section). Remove</p><p>and clean filter screen in wobble pump.</p><p>3. (100) Check all drains for leaks. Check fuel valve for leaks.</p><p>4. (100) Have someone actuate wobble pump to pressure fuel lines and check for leaks in</p><p>all fuel lines and connection from below cockpit floor to carburetor on engine.</p><p>Look for loose fittings and line chafing.</p><p>5. (100) Check for fuel line chafing from tank to header tank. Check fuel vent lines for</p><p>signs of chafing or leaks. Check security of header tank.</p><p>6. (100) Check Fuel tanks for leaks.</p><p>7.Annual: Drain fuel tanks and check “E” position on fuel receiver. (See page 15, Mainte-</p><p>nance Section).</p><p>8.Annual: Remove finger strainers (steel elbow) from fuel tank and clean.</p><p>9.Annual: Fill fuel tanks and check “F” position on fuel receiver.</p><p>10.Annual: Inspect throttle and mixture control rods for cracks and wear at fairleads. Check</p><p>security of connections to quadrant, bellcranks, and carburetor. Check smooth-</p><p>ness of operation and full travel between stops on carburetor.</p><p>OIL SYSTEM</p><p>1. (50) Check oil tank for security and snug clamps on oil lines at fittings. Check tank for</p><p>leaks.</p><p>2. (50) Check oil cooler mounting and check fittings for leaks.</p><p>3. (50) Check oil hoses for chafing or leaks.</p><p>4. (100) Remove oil sump plugs and examine cavity for metal particles. In a new installa-</p><p>tion, presence of particals does not necessarily mean trouble. Investigate, and if</p><p>no faults are discovered ground test with new oil. Re-check for metal particles</p><p>and if quantity present warrants engine change, also change oil, clean oil cooler,</p><p>oil tank, and lines.</p><p>Inspection Page 2 Air Tractor, Inc.</p><p>April 1, 1998 AT-401</p><p>(See Pratt & Whitney Maintenance Manual NO. 118611).</p><p>5. (100) Remove, disassemble, inspect and clean pressure oil strainer.</p><p>6. (100) Remove and clean the scavenge oil strainer, located in the rear of the sump under</p><p>the scavenge oil re-circulation line.</p><p>7. (100) Change oil. Drain the “Y” drain on the firewall and the three drains on the engine.</p><p>Remove the forward 9 spark plugs and after new oil is put in tank crank engine</p><p>with starter until oil pressure shows on the gauge. Replace the spark plugs and</p><p>harness. Safety oil “Y” drain and sump plugs.</p><p>INDUCTION SYSTEM</p><p>1. (50) Check the induction duct flexible connections for deterioration, splits, etc. and for</p><p>security of the hose clamps.</p><p>2. (50) Check the security of the backfire flap on the induction duct mounted on the</p><p>firewall. Inspect the spring inside the duct for wear and check that it holds the</p><p>flap firmly closed. Inspect the leather seal on the flap for deterioration.</p><p>3. (100) Check the carburetor hot air muff around the lower exhaust manifold for clear-</p><p>ance of the intake pipes, clearance of the exhaust sleeves, and cracks in the</p><p>corners. Check full travel of the hot air valve and be sure there is slight cable</p><p>pressure holding valve in “Cold” air position when the push-pull control on the</p><p>instrument pannel is pushed full in.</p><p>4. (100) Check the carburetor air induction screen for inspection and cleaning. The screen</p><p>is sandwiched between the carburetor inlet base and the casting that attaches to</p><p>it. The screen has a gasket (p/n 39505) on each side. If the screen is damaged or</p><p>clogged, replace or service it (p/n 47420).</p><p>5. (100) Visually inspect air filters (Fram p/n CA-161PL) for dirt accumulation and proper</p><p>sealing on each end. Clean filters if necessry by removing and with an airgun</p><p>blowing from the inside out. Replace when deterioration is obvious.</p><p>IGNITION SYSTEM</p><p>1. (100) Inspect, clean and gap (.015 - .018) the spark plugs.</p><p>2. (100) Inspect ignition cable assembly for loose connections, damaged spark plug leads,</p><p>chafing and security of mounting.</p><p>3. (100) Inspect spark plug lead ceramic connectors for presence of oil, dirt, cracks, or</p><p>chips.</p><p>4. (100) Check condition and security of magneto mounting and ground wires.</p><p>5. (100) Check ignition switch for proper operation. Check mags</p><p>available in various amounts of eccentricity and should be ordered</p><p>whenever the engine mount is replaced with a new one.</p><p>The oil tank is constructed of aluminum and rests on top of the engine mount structure.</p><p>The oil tank holds 8.0 gallons of oil and an additional 2 1/2 gallons is required to fill the oil lines</p><p>and engine crankcase.</p><p>Oil lines are 1.0" aluminum tubing from the tank to the “Y” drain and from the “Y” drain to</p><p>the engine inlet. Connections are with Mil-H-6000 1" hose. Lines from the engine outlet to the</p><p>cooler and from the cooler to the return port of the tank are also of Mil-H-6000 1" hose. The</p><p>firewall-mounted “Y” drain drains the tank and inlet lines. The engine is provided with three drain</p><p>points.</p><p>Carburetor heat is ducted from an aluminum muff on the lower segment of the exhaust</p><p>manifold to the hot air valve. Normal air is drawn through two Fram p/n ARP-2 pleated paper</p><p>filters. This model filter is also used on certain Piper aircraft and may be cleaned by removing and</p><p>with an airgun blowing from the inside out any dust or dirt which has accumulated. They may</p><p>also be washed with water and a good detergent several times until visible deterioration is</p><p>obvious. The air filter units are mounted on the firewall and for that reason remain clean for long</p><p>periods of time.</p><p>Since hot air robs horsepower, be sure that the lever arm on the hot air valve is in the fully</p><p>closed position and with a slight amount of cable pressure against the stop when the carb heat</p><p>control on the instrument panel is pushed full in.</p><p>The exhaust manifold is constructed of stainless steel and is attached to the cylinders with</p><p>two spacer washers so that all segments line up with each other before the clamps attaching the</p><p>segments are put in place. The clamps should not be over-tightened, and it should be possible to</p><p>rotate them after the bolts are snug by tapping with a small hammer.</p><p>FUEL SYSTEMFUEL SYSTEMFUEL SYSTEMFUEL SYSTEMFUEL SYSTEM</p><p>The AT-401 has two fuel tanks with a capacity of 63 gallons each. Both tanks gravity feed</p><p>into a small header tank which is located behind the chemical hopper and below the rear spar</p><p>attach tube.</p><p>The fuel valve handle is located within easy reach of the pilot and is marked “Main” and</p><p>“Off”. There can be no tank selection since both tanks are interconnected. The fuel valve placard</p><p>is marked “120 gallons usable”. This is due to the fact that the left-hand fuel tank sender has a</p><p>shorter float arm than the right hand tank and does not allow the last 3 to 4 gallons to be gauged.</p><p>Also a climb with no rudder correction for torque will result in approximately 3 gallons being</p><p>moved to the outboard wall of the right-hand tank which becomes unusable. For these reasons</p><p>only 120 gallons is counted usable although in straight and level co-ordinated flight, all the fuel</p><p>Description Page 4Description Page 4Description Page 4Description Page 4Description Page 4 Air Tractor, IncAir Tractor, IncAir Tractor, IncAir Tractor, IncAir Tractor, Inc</p><p>April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998 AT-401AT-401AT-401AT-401AT-401</p><p>may be used. The fuel gauge receiver, which is located on the instrument panel is marked in</p><p>fractions of 120 gallons.</p><p>Finger strainers of coarse wire mesh are located in each fuel tank. Fuel flows from the wing</p><p>tanks into the header tank, through the fuel valve and into the hand wobble pump which is used</p><p>to fill the lines before starting the engine. The hand wobble pump also serves as an emergency</p><p>fuel pump and has a fine-mesh filter screen installed which should be cleaned at various inter-</p><p>vals. A fuel drain is located on the wobble pump body.</p><p>A fuel pressure warning light is installed on the instrument panel and is set to activate</p><p>when fuel pressure falls below 2 psi.</p><p>There are four water traps in the fuel system: one in each wing tank, one in the header</p><p>tank, and one in the wobble pump. These drains should be activated daily. Each fuel tank has an</p><p>overboard vent located near the wing tip. With both tanks completely full, it is possible during</p><p>flight to vent a small amount of fuel overboard by skidding the aircraft or rolling sharply.</p><p>Fuel type for the AT-401 is aviation grade 80/87 minimum octane gasoline. If this fuel is not</p><p>available, use the next highest grade aviation gasoline, up to and including 100 octane. Under no</p><p>circumstances should aeromatic fuel be used.</p><p>An optional ferry fuel system (hopper fuel) may be installed by following the procedures and</p><p>using the parts described on drawing 50280-8.</p><p>TO INSTALL FERRY FUEL SYSTEMTO INSTALL FERRY FUEL SYSTEMTO INSTALL FERRY FUEL SYSTEMTO INSTALL FERRY FUEL SYSTEMTO INSTALL FERRY FUEL SYSTEM</p><p>1. Remove spray pump by disconnecting coupler at gatebox, disconnect brake cable at</p><p>pump, disconnect side discharge tube at spray valve and tube support on side of gatebox,</p><p>and uncouple pump at disconnect on pump strut.</p><p>2. Remove the bottom load tube between the gatebox and spray valve. Plug opening in</p><p>gatebox with furnished plug and tighten clamp.</p><p>3. Install screen per Note 5 Drawing 50280 in gatebox opening that supplied pump. Install</p><p>coupler, fittings and filter per Drawing 50280. Assemble all fittings with PR-1422-A2*. If</p><p>filter was used previously, disassemble and inspect for contamination. Safety coupler</p><p>arms with tyrap per drawing.</p><p>*Alternate sealer is TBM PKMMC236A1/2</p><p>4. Remove inspection cover from lower belly skin and route hose from fuel filter through hole</p><p>to plugged side of fuel valve. Hose must clear all flight controls.</p><p>5. Turn fuel valve pointer to "OFF" position. Remove plug from fuel valve, install fitting and</p><p>attach hose.</p><p>6. To use hopper fuel, rotate fuel selector handle CCW to second detent past "ON" position.</p><p>TO REMOVE FERRY FUEL SYSTEMTO REMOVE FERRY FUEL SYSTEMTO REMOVE FERRY FUEL SYSTEMTO REMOVE FERRY FUEL SYSTEMTO REMOVE FERRY FUEL SYSTEM</p><p>1. Turn fuel valve pointer to "OFF" position.</p><p>2. Remove hose and fitting at fuel valve and install plug.</p><p>3. Replace inspection cover in belly skin. Remove coupler, fittings, screen and filter from</p><p>gatebox.</p><p>4. Remove plug from bottom load tube opening in gatebox and install tube.</p><p>5. Install spray pump, plumbing and brake cable in reverse sequence to paragraph 1 under</p><p>To Install Ferry Fuel System above.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Description Page 5Description Page 5Description Page 5Description Page 5Description Page 5</p><p>AT-401AT-401AT-401AT-401AT-401 April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998</p><p>Description Page 6Description Page 6Description Page 6Description Page 6Description Page 6 Air Tractor, IncAir Tractor, IncAir Tractor, IncAir Tractor, IncAir Tractor, Inc</p><p>April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998 AT-401AT-401AT-401AT-401AT-401</p><p>ENGINE CONTROLSENGINE CONTROLSENGINE CONTROLSENGINE CONTROLSENGINE CONTROLS</p><p>A quadrant on the left-hand side of the cockpit incorporates the throttle, prop and mixture</p><p>controls. The throttle and mixture levers are attached to steel push rods with Fafnir REB3N</p><p>bearings attached. The prop control lever is attached to a 66-3425-2328 flexible control.</p><p>The throttle quadrant has a friction adjustment knob on the side to provide the desired</p><p>amount of friction on the levers. There are nylon and steel washers in the quadrant to isolate the</p><p>movement of one lever from the other. The steel washers have a square hole to prevent movement</p><p>on the square shaft. The square shaft should always press fit into the square hole of the</p><p>aluminum housing, and if loose, will cause one lever to cause movement of another.</p><p>OPTIONAL EQUIPMENTOPTIONAL EQUIPMENTOPTIONAL EQUIPMENTOPTIONAL EQUIPMENTOPTIONAL EQUIPMENT</p><p>Optional equipment for the Air Tractor includes a King KX155 NAV/COM unit. The Nav</p><p>Antenna is mounted on the canopy top.</p><p>The Com unit is mounted on the R/H cockpit wall within easy reach of the pilot. The Com</p><p>antenna is mounted on the fuselage top skin just</p><p>with engine running with</p><p>manifold pressure equal to field elevation (See Operation section).</p><p>6. (100) Clean the breaker compartments, distributor rotors and distributor blocks with a</p><p>clean dry cloth.</p><p>7. (100) Timing check: The breaker points on both magnetos should just open, simultane-</p><p>ously when the piston is 25 degrees before top center. Refer to P&W Maintenance</p><p>Manual No. 118611 for breaker point adjustments and further timing instruc-</p><p>Air Tractor, Inc. Inspection Page 3</p><p>AT-401 September 15, 1989</p><p>tions.</p><p>MAIN LANDING GEAR AND BRAKES</p><p>1. (50) Inspect tires for cuts, wear and inflation. (43 psi).</p><p>2. (50) Inspect brakes for lining wear, condition of disc, brake fluid leaks, etc. Check</p><p>torque plate for cracks. Inspect inside and outside edges of wheel for cracks.</p><p>Inspect for security of brake line.</p><p>3. (100) Check master cylinders for leaks, test firmness of brakes and bleed if necessary,</p><p>check for ample fluid in brake reservior.</p><p>4. Annual: Check main gear clamp block for straightness with straight edge. Check attach</p><p>bolts visually. A minor bow to conform to gear spring is acceptable.</p><p>5. (100) Check operation of parking brake and look for leaks.</p><p>6. (100) Check torque on main gear attach bolts: (See page 7 of Maintenance Section.)</p><p>7. (100) Check main gear leg visually for cracks, nicks or corrosion.</p><p>8. As Rqd. Change main gear bolts in accordance with schedule on page 7 through 8 of this</p><p>manual. Change landing gear spring in accordance with Service Letter #104.</p><p>9. (1,000): Hoist aircraft in accordance with hoisting instructions and check for looseness in</p><p>main gear attachments. This would be a good time to change any bolts that are</p><p>nearing end of safe life.</p><p>TAIL GEAR</p><p>1. (50) Inspect tire for wear and inflation (35psi).</p><p>2. (50) Check lock pin operation and condition of centering springs.</p><p>3. (100) Jack tail wheel clear of ground and check for looseness of housing on spring (See</p><p>page 9 of Maintenance Section). Torque bolts to 1,700 inch-pounds torque.</p><p>4. (100) With tale wheel off ground, rotate wheel for signs of dry wheel bearings. Check for</p><p>looseness on axle, check locking pin for free engagement to fork, check fork for</p><p>looseness in housing, check for wear on brass wear plate.</p><p>5. As Rqd. Change tail gear bolts in accordance with schedule on page 7 through 8 of this</p><p>manual. Change tail gear spring as suggested on page 9.</p><p>6. Annual: Remove tail wheel lock pin housing, slide out locking pin, and check for straigh-</p><p>ness and wear. Lubricate, re-install and check alignment as called out on page 7</p><p>of the Maintenance section of this manual.</p><p>7. Annual: Jack under the stabilizer strut fitting and check for looseness of tail spring to the</p><p>fueslage frame. Also change the forward spring attach bolt. Check condition of</p><p>aluminum pad under spring.</p><p>8. (100) Check tail gear spring visually for cracks or nicks.</p><p>9. Annual: Check distance from clamp block to floor for evidence of yielding (See page 7 of</p><p>the Maintenance section). After 1,000 hours make this check every 50 hours.</p><p>Inspection Page 4 Air Tractor, Inc.</p><p>April 1, 1998 AT-401</p><p>FUSELAGE FRAME</p><p>1. (100) Check for cracks in upper and lower aft fuselage structure, especially upper aft</p><p>L/H longeron per S/L #195. Check for cracks around tail spring attach area.</p><p>Check for cracks around main gear attach area.</p><p>2. (100) Inspect engine mount attach bushings and surrounding tubes for cracks. Inspect</p><p>area around wing attach bushings for cracks.</p><p>3. (100) Inspect all other highly stressed areas for cracks such as rear spar fittings, skin</p><p>attach brackets, spray boom attach tubes, flap control attachments, control stop</p><p>brackets, etc.</p><p>4. (100) Check condition of paint and re-finish where necessary.</p><p>FUSELAGE FIXED SKINS</p><p>1.Annual: Tighten all screws attaching the fixed skins. Look for elongated holes in the</p><p>angles if loose screws are found.</p><p>2.Annual: Inspect for cracks or corrosion on all fixed skins. A corroded part should be</p><p>replaced or else stripped and re-painted as called out in the Maintenance section.</p><p>3. (100) Inspect dispersal equipment boots at fuselage skin attachments for wear.</p><p>4. (100) Inspect for skins chafing on other parts, such as the vertical fin, or in the area</p><p>around the tail spring.</p><p>CONTROL SYSTEM</p><p>1. (100) Check rudder cables for wear at pulley locations and at entrance to fuselage.</p><p>2. (100) Check tail wheel lock cable for wear at pulley and at entrance to fuselage. Check</p><p>spring on end of lock cable for wear.</p><p>3. Annual: Check for wear in the aluminum rudder adjust channel.</p><p>4. (2,000) Remove rudder pedal castings and check for cracks around bronze bushings. Also</p><p>check bushings in master cylinder attach strap.</p><p>5. Annual: Check rudder pedal attach brackets and tube for cracks.</p><p>6. (100) Check all aileron push-rods and bellcranks for bearing condition, clearance to</p><p>other parts, loose check nuts, end-play in bellcranks.</p><p>7. (100) Check all elevator push-rods and bellcranks for bearing condition, clearance to</p><p>other parts, loose check nuts, end -play on bellcranks, wobble in idlers.</p><p>8. (100) Check cockpit controls for end-play or slack.</p><p>9. (100) Check for missing neoprene washers at aileron and elevator stops.</p><p>10. (100) Cycle flaps and listen for unusual rubbing noises. Check for wobble in 90o flap</p><p>bellcranks, and torque on the AN6 attach bolts. Check for bent arms on the 90o</p><p>bellcranks, Check that flaps do not exceed markings in down position.</p><p>11. (100) Check rubber coupling in flap motor connection. Check for loose wires around</p><p>flap actuator.</p><p>12. (100) Check elevator tab free play (Not to exceed .20" total travel.)</p><p>13. (100) Read Maintenance section on Rudder Controls, Elevator Controls, Cockpit Con-</p><p>trols, and Trim Tab Controls and perform inspections called out in those sections.</p><p>Air Tractor, Inc. Inspection Page 5</p><p>AT-401 March 30, 2003</p><p>Inspection Page 6 Air Tractor, Inc.</p><p>December 10, 2019 AT-401</p><p>14. (100) Read Maintenance section on Gate Box Controls, Spray Lever Controls and perform inspections</p><p>called out in those sections.</p><p>15. (300) Visually inspect the flap actuator attachment plates on the flap torque tube per SL 347.</p><p>16 (900) Perform a dye penetrant inspection of the flap actuator attachment plates on the flap torque</p><p>tube per SL 347.</p><p>WINGS</p><p>1. Annual: Remove inspection covers and check for cracks in ribs or spar webs.</p><p>2. Annual: Inspect wing skins for cracks, loose rivets, and for corrosion. Keep clean.</p><p>3. Annual: Inspect wing attach angles for signs of wear, cracks, or missing nuts. (See Service Letter #89A)</p><p>4. (1,000) Remove and inspect the rear spar bolt per instructions on page 12 of Maintenance section).</p><p>5. (2,000) Remove hopper and check the wing center splice connection as described on page 12 of the</p><p>Maintenance section of this manual.</p><p>AILERONS</p><p>1. Annual: Check condition of counterweight attachment.</p><p>2. Annual: Check condition of aluminum hinges and attachment to spar, check steel hinges for corrosion</p><p>or cracks.</p><p>3. Annual: Check aileron push-rods for cracks in threads and bearing condition.</p><p>4. Annual: Inspect all skins, spar, and ribs for cracks, loose rivets. Inspect around counterweight support</p><p>structure for cracks.</p><p>5. Annual: Check aileron travel: 20o up, 14o down, +/-1o.</p><p>FLAPS</p><p>1. Annual: Check condition of steel hinges and attachments to spar, per S/L #216.</p><p>2. Annual: Inspect flap push-rods for bearing alignment, dragging on other parts, freedom of movement.</p><p>3. (2,000) Replace the RE4M6 bearing on the aft end of the flap push-rods.</p><p>4. (100) With flaps full down, move ailerons through full travel to check clearance between flap and</p><p>aileron push-rods.</p><p>5. Annual: Inspect all skins, spar, and ribs for cracks, loose rivets or corrosion.</p><p>6. Annual: Check flap travel and rigging. (See Page 18 of Maintenance section).</p><p>EMPENNAGE</p><p>1. (100) Check vertical fin front spar attach bolt torque at fuselage fittings (420 inch-pounds at nut),</p><p>and for installation</p><p>of a steel doubler plate per S/L #155 if required.</p><p>2. (100) Inspect vertical fin rear spar for cracks above top longeron connection.</p><p>3. Annual: Check torque on all bolts connecting rudder and elevators to fixed surfaces and at elevator</p><p>horn connection to pedestal and push-rod. Torque should be 100 inch-pounds at the nut.</p><p>4. Annual: Check stabilizers and vertical fin for skin cracks, loose rivets, cracks in spars, ribs, corrosion.</p><p>Air Trac t or, Inc . Ins pe c t io n Page 7</p><p>AT-4 0 1 Fe bruary 9 , 2 0 1 2</p><p>5 . (10 0) Ch eck t r im ta b a t ta ch m en ts to eleva tors . Ch eck h orn .</p><p>6 . (10 0) In s p ect ru d der ca b les for fra yin g.</p><p>7 . (10 0) Ch eck s ta b ilizer a t ta ch in g pedes ta l for cra ck s p er S/ L # 1 80 A. Wh en th e</p><p>rep la cem en t pedes ta l is in s ta lled , in s pect ion s m a y b e p er form ed on a n a n n u a l</p><p>ba s is .</p><p>8 . (10 0) In s p ect for cor ros ion on in tern a l h or izon ta l s ta b ilizer b ra ces per S/ L #9 8 .</p><p>9 . An n u a l: Rem ove ga p covers from s ta b ilizers a n d ch eck torqu e on b olts a t ta ch in g s t a b ilizers</p><p>to fu s ela ge.</p><p>10 . An n u a l: In s p ect s ta b ilizer s t ru t s a n d fit t in gs for cor ros ion a n d eros ion a s refer en ced in</p><p>S/ L #1 98 . Ch eck bolt torqu e a n d s n u g ch eck n u ts .</p><p>11 . An n u a l: In s p ect a ll eleva tor a n d ru d der h in ges for wea r .</p><p>12 . An n u a l: In s p ect b u s h in gs a n d b olts th rou gh ru d der h orn for wea r .</p><p>13 . An n u a l: Ch eck con t rol s u r fa ce t r a vel: E leva tors 2 8 o u p , 1 6 o d own . Ru d der t ra vel 21 o R. or</p><p>L. All t ra vels +/ -1 o.</p><p>14 . An n u a l: Ch eck eleva tor t r im ta b t ra vel: 11 o u p , 1 0 o down , +/ - 1 1 / 2 o.</p><p>15 . (13 5 0) For p la n es th rou gh s / n 40 1 -0 70 0 rep la ce eyeb olts in s ta b ilizer a t s t ru t fit t in gs per</p><p>S/ L #1 29 .</p><p>COCKPIT</p><p>1 . (10 0) Ch eck con dit ion of s ea t belt a n d s h ou ld er h a r n es s .</p><p>2 . An n u a l: If Am Sa fe Airb a g s ys tem is in s ta lled , p er form in s pect ion a n d fu n ct ion a l tes t of</p><p>s ys tem in a ccord a n ce with Am Sa fe Docu m en t E5 10 5 00 .</p><p>3 . An n u a l: Ch eck in s t ru m en t lin es for lea k s , ch a fin g, s ecu r ity.</p><p>4 . An n u a l: Ch eck win d s h ield a n d ca n opy d oor gla s s for m is s in g s crews , cra ck s , s cra tch es , or</p><p>cra zin g.</p><p>5 . An n u a l: Ch eck con dit ion of m a rk in gs on in s t ru m en ts a n d p la ca rd con dit ion .</p><p>6 . (10 0) Ch eck d oor h in ges a n d la tch es for s n u g. In s p ect wea th ers t r ip p in g a rou n d d oor</p><p>fra m e.</p><p>7 . (10 0) Ch eck con d it ion of s ea t covers .</p><p>8 . (10 0) Ch eck ra d io b ox fa s ten er s .</p><p>9 . (10 0) Per form ra d io opera t ion a l ch eck .</p><p>DISPERSAL EQUIPMENT</p><p>1 . (10 0) Ch eck ga te box s ea l for lea ks , ch eck bot tom loa d fla n ge on ga te b ox for lea ks ,</p><p>ch eck ga te b ox a t ta ch m en t to h opp er for lea ks .</p><p>2 . (10 0) Ch eck con dit ion of h opp er lid ga s k et . Repla ce if requ ired .</p><p>3 . (10 0) Ch eck s pra y p u m p s t ru t over -cen ter la tch es for ten s ion a n d s a fety p os it ion .</p><p>4 . (10 0) Ch eck to s ee if p lu m bin g on d is ch a rge s ide of pu m p is s a fety-wired to top of</p><p>pu m p.</p><p>5 . (10 0) Ch eck bot tom loa d in g p lu m bin g con n ect ion to con t rol va lve a s loos e cla m ps will</p><p>b low off p lu m bin g h ere.</p><p>6 . (10 0) Ch eck boom a t ta ch a rm s for s ecu r ity. Ch eck b oom con n ect ion s to boom “Tee” for</p><p>lea k s .</p><p>7 . (10 0) In s p ect a ll qu ick -cou pler s to s ee if cou p ler a rm s a re s a fety wired togeth er .</p><p>8 . (10 0) Clea n s t ra in er s creen a n d ch eck O-r in g s ea l.</p><p>9 . (10 0) Ch eck con t rol va lve for lea k s or loos e ba ll.</p><p>10 . (10 0) Ch eck a ll h os es for d eter iora t ion . Tigh ten a ll h os e cla m p s .</p><p>11 . (10 0) Ch eck for loos e h ex n ip p les a n d loos e n ozzles in boom s .</p><p>12 . (10 0) Ch eck con dit ion of b oom pres s u re ga u ge, t u b in g, a n d con n ect ion to ga u ge a n d</p><p>boom .</p><p>13 . (10 0) Ch eck fa n bra ke lever for p roper a d ju s tm en t . Rota te fa n with b ra ke off to ch eck</p><p>for d ra g.</p><p>14 . (10 0) Ch eck b ot tom loa d va lve for lea ks . Rem ove s h im s if worn .</p><p>LUBRICATION SCHEDULE:LUBRICATION SCHEDULE:LUBRICATION SCHEDULE:LUBRICATION SCHEDULE:LUBRICATION SCHEDULE:</p><p>Daily: Daily: Daily: Daily: Daily: (Use general purpose grease)</p><p>1. Grease fitting on tail wheel (if in rice operations).</p><p>2. Grease fitting on tail wheel housing (if in rice operations).</p><p>3. Grease fitting on lock pin housing (if in rice operations).</p><p>4. For row-crop work perform the above on a weekly basis.</p><p>Every 100 Hours:Every 100 Hours:Every 100 Hours:Every 100 Hours:Every 100 Hours: (Use general purpose grease)</p><p>1. Jack tail wheel off ground, remove fork from housing, clean and grease bronze bushings</p><p>and wear plate by hand packing.</p><p>2. Remove tail wheel axle bolt, axle, disassemble tail wheel parts and clean and hand-pack</p><p>tail wheel bearings.</p><p>3. Grease fitting on both ends of control torque tube housings on cockpit floor.</p><p>4. Apply touch of grease to striker plate at door handles.</p><p>5. Apply touch of grease to Spray pump brake lever slot.</p><p>6. Apply touch of grease to trim push rods at fairlead locations.</p><p>7. Grease fitting on wobble pump handle.</p><p>8. Remove and pack main wheel bearings if conditions require it.</p><p>9. Apply grease to worm drive of Micro-control on spray lever and micro-adjust worm drive</p><p>on hopper handle.</p><p>Every 100 Hours:Every 100 Hours:Every 100 Hours:Every 100 Hours:Every 100 Hours: (Use general purpose oil)</p><p>1. Door handles.</p><p>2. Clevis ends on throttle lever, prop and mixture levers.</p><p>(Caution: No oil on quadrant.)</p><p>3. Control lock attachments at panel.</p><p>4. Trim tab hinges on elevators.</p><p>5. Trim push-rods at idler and horn connections.</p><p>6. Tail wheel lock cable pulley bearing.</p><p>7. Tail wheel lock cable spring at eyebolt connection.</p><p>8. Centering spring bushing on tail wheel fork cap arm.</p><p>9. Shackle at end of tail wheel lock cable.</p><p>10. Bushing and bolt in ends of rudder horn.</p><p>11. Latch arm on seat belt.</p><p>12. Latch arms and adjust threads on hopper lid latch assy.</p><p>13. Both ends of hopper gate push-rod outside aircraft.</p><p>14. Latch cams on fuel filler caps.</p><p>15. Oil seat rail tubes in damp climates to prevent corrosion.</p><p>16. Micro-switch rollers on arms.</p><p>17. Bronze bushings in rudder pedal to master cylinder strap attach.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Lubrication Page 1Lubrication Page 1Lubrication Page 1Lubrication Page 1Lubrication Page 1</p><p>AT-401AT-401AT-401AT-401AT-401 September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989</p><p>Lubrication Page 2Lubrication Page 2Lubrication Page 2Lubrication Page 2Lubrication Page 2 Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.</p><p>September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989</p><p>Every Annual Inspection:Every Annual Inspection:Every Annual Inspection:Every Annual Inspection:Every Annual Inspection: (Use general purpose grease).</p><p>1. Clean and hand pack the Torrington bearings in the rear elevator idler.</p><p>2. Clean and hand pack the Torrington bearings in the 90° bellcranks attached to the flap</p><p>torque tube.</p><p>Every Annual Inspection:Every Annual Inspection:Every Annual Inspection:Every Annual Inspection:Every Annual Inspection: (Use general purpose oil)</p><p>1. Remove flap actuator at fuselage rear spar tube and oil the bronze bushing and the steel</p><p>spacer bushing.</p><p>2. Remove the trim idler attached to the rear part of the fuselage frame and</p><p>oil the bronze</p><p>bushing and steel spacer bushing.</p><p>3. Remove the spray lever and oil the bronze bushings inside.</p><p>4. Remove the gate push-pull tube outside the fuselage and oil the bronze bushing in the</p><p>forward end and the bearing in the aft end.</p><p>AT-401AT-401AT-401AT-401AT-401</p><p>FUSELAGE FRAME REPAIRSFUSELAGE FRAME REPAIRSFUSELAGE FRAME REPAIRSFUSELAGE FRAME REPAIRSFUSELAGE FRAME REPAIRS</p><p>The most common cause of fuselage frame damage is a landing gear strike during spraying</p><p>operations, or hitting an obstruction during take-off. A severe drag load is placed on the main</p><p>gear leg and due to the leverage that exists,either the tubular structure is damaged or else the</p><p>forward clamp block bolt fails. If the tubular structure is severely damaged it is best to contact</p><p>the factory with photos or sketches of the damaged tubes, and a repair cluster can be constructed</p><p>at the factory which can be spliced in a convenient location with external sleeves.</p><p>It is seldom necessary to place the fuselage frame in the original jig, as shop aids can be</p><p>sent with the repair structure, and with careful measurements, the structure will be back to the</p><p>original configuration. Repair clusters are designed so that gas welding can usually be used to</p><p>install the new cluster. Standard repairs may be made in accordance with AC 43.13-1A.</p><p>FORWARD CLAMP BLOCK BOLT FAILUREFORWARD CLAMP BLOCK BOLT FAILUREFORWARD CLAMP BLOCK BOLT FAILUREFORWARD CLAMP BLOCK BOLT FAILUREFORWARD CLAMP BLOCK BOLT FAILURE</p><p>If the wheel strike has caused the forward clamp block bolt to break, it is likely that the gear</p><p>leg has folded back under the aircraft and broken the large inboard attach bolt and the aft clamp</p><p>bolt. When the large inboard bolt fails, it usually damages the 1 3/8" OD bushing that it was</p><p>attached to, and as the gear folds back the sharp edge of the gear leg damages the 2 1/2"</p><p>diameter tube that the bushing is welded to.</p><p>The broken bolts can be removed from the attach fitting by the conventional practice of</p><p>drilling into the broken off bolt shank and using an “Easy Out” tool to remove the bolt shank. Be</p><p>careful not to damage the threads, but if there appears to be slight thread damage, use a 3/4 - 16</p><p>bottoming tap with a generous amount of cutting oil to re-work the threads, making sure that the</p><p>tap is started exactly with the original threads.</p><p>The damage to the 1 3/8"OD bushing is usually confined to the rear lower side, where the</p><p>1.0" bolt has bent before failing. The factory practice is to use a heli-arc welding machine and</p><p>with weld rod build back the area on the inside of the bushing as shown on the enclosed drawing.</p><p>Also, the damage to the 2 1/2" diameter tube can be filled with welding rod, and the diamond</p><p>shaped plate of .125 4130N can be welded in place as shown. Since the 2 1/2" tube is 1/4" thick</p><p>and the bushing is also heavy wall, conventional arc-welding is permissible if the operator is</p><p>skilled, and a high-test rod is used. Gas welding is possible, but due to the very thick parts</p><p>involved, a large torch at high flame settings will be required.</p><p>After welding, clean, sand, etch, prime and finish coat as described under “Painting Steel</p><p>Parts” in the maintenance section.</p><p>THREADS STRIPPED OUT IN FORWARD CLAMP BLOCK ATTACH FITTINGTHREADS STRIPPED OUT IN FORWARD CLAMP BLOCK ATTACH FITTINGTHREADS STRIPPED OUT IN FORWARD CLAMP BLOCK ATTACH FITTINGTHREADS STRIPPED OUT IN FORWARD CLAMP BLOCK ATTACH FITTINGTHREADS STRIPPED OUT IN FORWARD CLAMP BLOCK ATTACH FITTING</p><p>If the wheel strike has caused the threads to fail instead of the bolt in the forward gear</p><p>attach bolt location, it is necessary to drill out the old threads, cut new ones, and install a</p><p>helicoil. This requires certain tools and coils which are listed below:</p><p>1 ea. 49/64" drill bit with 1/2" shank</p><p>1 ea. CTF-12RUP-00 rough tap (Tridair Industries)</p><p>1 ea. CTF-12SRP-H3 finish tap (Tridair Industries)</p><p>1 ea. CIF-12 winding tool (Tridair Industries)</p><p>1 or more TNF-12C-0750 helicoils (Tridair Industries)</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Repairs Page 1Repairs Page 1Repairs Page 1Repairs Page 1Repairs Page 1</p><p>AT-401AT-401AT-401AT-401AT-401 May 2, 1994May 2, 1994May 2, 1994May 2, 1994May 2, 1994</p><p>These tools are in stock at the factory and with Air Tractor dealers. In addition, it is</p><p>necessary to have a new p/n 40148-1 attach block since the old block will bend as the bolt is</p><p>being stripped out. Also, new set of main gear bolts is necessary.</p><p>The procedure for installing the helicoil is as follows:</p><p>1. Take the new 40148-1 block to the drill press and enlarge one of the 3/4" holes to</p><p>49/64. The reason is that the block will be used for a drill guide for drilling out the old</p><p>threads in the fuselage frame.</p><p>2. Hoist the aircraft as described in “Hoisting” in the maintenance section and install</p><p>barrels with boards under each wing tie-down fitting to steady the aircraft. Attach the 3/4"</p><p>hole in the 40148-1 block to the rear of the fuselage fitting so that the 49/64" hole is</p><p>opposite the damaged thread that are to be drilled out.</p><p>3. A slow turning powerful 1/2" electric drill motor is required. Before drilling is com-</p><p>menced, center the 49/64" hole in the clamp block exactly over the damaged threads and</p><p>use a large “C” clamp to hold the block solidly in place. Torque the aft bolt to help hold the</p><p>block and prevent it from moving.</p><p>4. Use generous amounts of cutting oil on the drill bit tip (have someone apply it with a</p><p>brush every few seconds during drilling). The drill will try to “grab” every few revolutions</p><p>and it is best to trigger the switch on and off as you go to prevent the bit from being broken</p><p>as this can very easily happen and you will be out of business until another bit can be</p><p>obtained.</p><p>5. Insert the 49/64" drill bit into the clamp block being used as a drill guide, position the</p><p>drill motor with your body to provide a straight hole, and cautiously start the drilling</p><p>operations as described above. It is not necessary to drill through the lower longeron tube,</p><p>so when the drill reaches that point, pull it out.</p><p>6. Now you have the 49/64" hole through the forward end of the fuselage fitting. Remove</p><p>the clamp block and start the rough tap by hand into the hole, using plenty of thread</p><p>cutting oil applied with a small hand pump can. The rough tap will center itself with the</p><p>hole, but it is adviseable to start it as straight as possible.</p><p>7. After the rough tapping operation is complete, blow out any shavings and start the finish</p><p>tap, picking up the exact threads and again using plenty of thread cutting oil. Back out the</p><p>tap every few turns, removing shavings and applying cutting oil. When the finish tap is</p><p>removed, blow out all cuttings and inspect the hole.</p><p>8. Determine how far the helicoil is to be inserted into the fitting. The insertion depth can</p><p>be determined by placing the 40148-1 block against the fuselage fitting with all of the</p><p>shims to be used between the two parts. Then apply the MS20002C12 washer under the</p><p>bolt head of the NAS152DH40 bolt and place the bolt on the side of the block and fuselage</p><p>fitting to determine the point inside the fuselage fitting the threads on the bolt will be</p><p>located. It is adviseable to have the helicoil located two or three threads deeper inside the</p><p>fitting so there is no chance the helicoil will bottom out on the bolt shank before the bolt is</p><p>fully torqued. Mark this position on the outside of the fitting which represents the start of</p><p>the helicoil when it is installed. Since the helicoil is 3/4" long when installed, measured</p><p>another 3/4" past your mark to determine the deepest position of the helicoil. Now measure</p><p>from the deepest mark to the surface of the fitting and install the helicoil on the winding</p><p>tool and adjust the top on the winding tool to correspond with that measurement.</p><p>Repairs Page 2Repairs Page 2Repairs Page 2Repairs Page 2Repairs Page 2 Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air</p><p>Tractor, Inc.Air Tractor, Inc.</p><p>April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998 AT-401AT-401AT-401AT-401AT-401</p><p>Proceed to install the helicoil with the winding tool and if the setting is correct the</p><p>winding tool will place the helicoil in the correct location when the stop is reached. Remove</p><p>the winding tool and re-check the helicoil position. Test the position by installing the bolt,</p><p>shims, block and applying full torque to the bolt (3,000 inch-pounds). The helicoil is held in</p><p>place by spring tension and will not back out.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Repairs Page 3Repairs Page 3Repairs Page 3Repairs Page 3Repairs Page 3</p><p>AT-401AT-401AT-401AT-401AT-401 September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 1</p><p>February 9, 2012</p><p>Figures Page 2</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 3</p><p>February 9, 2012</p><p>Figures Page 4</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 5</p><p>February 9, 2012</p><p>Figures Page 6</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 7</p><p>February 9, 2012</p><p>Figures Page 8</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 9</p><p>February 9, 2012</p><p>Figures Page 10</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 11</p><p>February 9, 2012</p><p>Figures Page 12</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 13</p><p>February 9, 2012</p><p>Figures Page 14</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 15</p><p>February 9, 2012</p><p>Figures Page 16</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 17</p><p>February 9, 2012</p><p>Figures Page 18</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 19</p><p>February 9, 2012</p><p>Figures Page 20</p><p>February 9, 2012</p><p>Air Tractor Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 21</p><p>February 9, 2012</p><p>Figures Page 22</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>Figures Page 23</p><p>February 9, 2012</p><p>Figures Page 24</p><p>February 9, 2012</p><p>Air Tractor, Inc.</p><p>AT-401</p><p>AT-401_OM-0-Introduction</p><p>AT-401_OM-1-Description</p><p>AT-401_OM-2-Operation</p><p>AT-401_OM-3-Maintenance</p><p>AT-401_OM-4-Schematics</p><p>AT-401_OM-5-Inspection</p><p>AT-401_OM-6-Lubrication</p><p>AT-401_OM-7-Repairs</p><p>AT-401_OM-8-Figures-1</p><p>AT-401_OM-9-Radial_Engine_Tune-Up</p><p>aft of the canopy shell. Jacks for the Com unit</p><p>are located on the R/H cockpit wall.</p><p>A night lighting system is also optional for the Air Tractor. This system consists of Whelen</p><p>strobe/position lights on the wing tips and a position light mounted on the rudder trailing edge.</p><p>For cockpit lighting, Grimes eyebrow lights are mounted over the instruments, with post lights for</p><p>switches. A dome light is located on the upper R/H side of the windshield. All instrument lights</p><p>and the dome light are connected to a rheostat to control light intensity.</p><p>For international flights a King KR 87 ADF may be conveniently located on the R/H side of</p><p>the cockpit wall. A King Transponder may also be packaged with the ADF. Glide slope is optional.</p><p>For working at night two 600 watt retractable lights are used for the forward lighting. Turn</p><p>lights are two 250 watt plug-in lights that can be adjusted as the pilot desires. These lights are</p><p>located on the rear spar of the wing at the wing tip. Servicing of all lights is done by removing the</p><p>fiberglass wingtip.</p><p>For drag reduction and a smoother airflow around the empennage a fiberglass ring cowl is</p><p>installed around the engine cylinders.</p><p>Other options include Cleveland 29 x 11 high-flotation tires and wheels with dual 3-piston</p><p>brakes, a windshield washer, and a ferry fuel system that allows the hopper to be used as a fuel</p><p>tank. A 3-piece windshield with wiper and a hopper rinse tank are also optional.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Description Page 7Description Page 7Description Page 7Description Page 7Description Page 7</p><p>AT-401AT-401AT-401AT-401AT-401 April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998</p><p>PROPELLER AND GOVERNORPROPELLER AND GOVERNORPROPELLER AND GOVERNORPROPELLER AND GOVERNORPROPELLER AND GOVERNOR</p><p>The propeller used is a Hamilton Standard 12D40 hub with 6101A-12 blades. The oil seal</p><p>used in the hub is a “Little Giant” p/n 40-103.</p><p>The propeller is a constant-speed type and is controlled with a Hamilton Standard p/n</p><p>1M12-G governor. This governor is attached to the nose case of the engine and has a p/n 128290</p><p>gasket between nose case and governor mounting face.</p><p>Governor adjustment should allow 2250 RPM on take-off.</p><p>Optional propeller is the Hamilton Standard 22D40-507 hub with AG200-2 blades. This</p><p>propeller requires Hamilton Standard p/n 4G10-21 governor. Since the optional propeller is the</p><p>Hydromatic type, all parts are fully enclosed and protected from dirt. Aircraft performance is the</p><p>same with either propeller.</p><p>To be able to install the optional hydromatic propeller, the engine crankshaft must have</p><p>been modified previously. Evidence of this modification may be seen by examining the end of the</p><p>crankshaft.</p><p>If the crankshaft is threaded on the inside as well as outside, it is in the hydromatic</p><p>configuration. If it is not threaded, it will be necessary to wait until engine overhaul time and</p><p>have the crankshaft modified for hydromatic configuration at that time.</p><p>ELECTRICAL SYSTEMELECTRICAL SYSTEMELECTRICAL SYSTEMELECTRICAL SYSTEMELECTRICAL SYSTEM</p><p>The AT-401 is equipped with either the Skytronics p/n 7555T 30 amp alternator or the</p><p>Skytronics p/n 7655T 60 amp alternator. The 30 amp alternator is installed on engines arriving</p><p>at the factory that have a 1 1/2 to 1 generator drive ratio. The 60 amp alternator is installed on</p><p>engines that have a 2 to 1 generator drive ratio. Both alternators use the same Skytronics p/n</p><p>J12M24SP voltage controls. Wiring is identical for the two alternators. Both alternators are 28</p><p>volt and have a voltage adjustment screw. The 30 amp alternator will handle all normal electrical</p><p>loads except for the night working lights. When work lights are installed the 60 amp alternator</p><p>must be used. If the engine is not equipped with the required 2 to 1 generator drive, this drive</p><p>assembly, along with a different starter jaw can be obtained from most R1340 engine overhaul</p><p>shops.</p><p>For cooling, both use a 2-inch diameter blast tube.</p><p>The starter solenoid is mounted on the firewall and is a Cutler Hammer p/n 6041H202A.</p><p>This relay is sealed around the perimeter of the barrel with PRC-1422 A-2 sealer, and three No.</p><p>50 drain holes are drilled in the plastic cap before installation. This will protect the relay during</p><p>engine wash-downs.</p><p>The master relay is mounted on the battery platform and is also a Cutler Hammer p/n</p><p>6041H202A, but without the drain holes and sealed only on the top and sides of the barrel. Any</p><p>Cutler Hammer relay that is replaced should be sealed and drilled as described above. Alternate</p><p>relay is the Kissling p/n 29.314.12.903 which is sealed.</p><p>The battery is a Teledyne Gill p/n GE-51C. The starter is a Jack & Heintz JH3-L. The wire</p><p>bundle through the firewall is secured with silicone sealer to prevent vibration from chafing the</p><p>wires.</p><p>A wiring schematic is provided.</p><p>Description Page 8Description Page 8Description Page 8Description Page 8Description Page 8 Air Tractor, IncAir Tractor, IncAir Tractor, IncAir Tractor, IncAir Tractor, Inc</p><p>April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998 AT-401AT-401AT-401AT-401AT-401</p><p>Air Tractor, Inc. Description Page 9</p><p>AT-401 January 12, 2009</p><p>COCKPIT</p><p>The AT-401 has exceptional visibility on the ground as well as in the air. A large one-piece</p><p>plexiglass windshield is used, and cockpit entry is made through either of two large canopy doors.</p><p>A wire deflector is installed on the centerline of the aircraft in front of the windshield.</p><p>The rudder pedals may be adjusted on the ground by removing the “T” pin and sliding the</p><p>rudder pedals in the aluminum channel to the desired position and reinserting the “T” pin. The</p><p>seat is fixed in one position at the factory. However, the operator may lower the seat if desired by</p><p>removing the two pins and drilling new holes through the seat rail. The seat structure is of welded</p><p>413ON tubing, oiled internally, sand blasted, primed and painted. The covers are removable and</p><p>may be changed as required. The covers are of a coarse mesh nylon material for comfort during</p><p>hot weather. At the bottom extreme of the seat a tube structure supports a thick Ensonite pad to</p><p>protect the pilot should the nylon covering fail in a severe crash.</p><p>A three-inch wide nylon safety belt is attached to the seat structure. The shoulder harness is</p><p>attached to the primary fuselage structure behind the cockpit. A control lock is located under the</p><p>panel and hinges up to secure the control stick. If the aircraft is equipped with AmSafe Airbags,</p><p>these airbags are built into the shoulder harnesses. The airbag system is equipped with its own</p><p>internal battery, so it is always active. There is no pilot action necessary to arm or operate the</p><p>system. The airbag system requires the use of the installed crotch strap for proper pilot</p><p>protection</p><p>The instrument panel is slanted forward for better visibility. Instruments provided with the</p><p>basic AT-401 include a sensitive altimeter, airspeed indicator, oil temperature, oil pressure, fuel</p><p>pressure gauge, tachometer, manifold pressure gauge, compass, boom pressure gauge, fuel gauge</p><p>and voltmeter. A stall warning horn is provided and the lift detector on the wing is set to activate</p><p>the horn at approximately 5 to 8 miles per hour above stall. A hopper quantity gauge is installed</p><p>in the upper panel on the right-hand side. This gauge is marked to read in U.S. gallons with the</p><p>aircraft in the ground attitude.</p><p>A large window is installed on the rear hopper wall so that the pilot can see the last bit of</p><p>chemical as it leaves the hopper. The hopper window is supported with an aluminum frame and is</p><p>sealed with silicone sealer which is impervious to most chemicals and readily available at most</p><p>industrial stores.</p><p>The cockpit has aluminum enclosure skins and control push-rod boots which isolate the</p><p>cockpit from the rest of the aircraft and prevent the entry of most chemicals. If the</p><p>aircraft is</p><p>used for dusting however, the operator should install boots around the rudder cables where they</p><p>pass through the cockpit wall and re-seal small cracks and seams with silicone sealer.</p><p>CONTROL SYSTEM</p><p>Push-pull tubes are used in both the aileron and elevator control system. Rod-end bearings</p><p>are installed in each push-rod to minimize control system friction. The torque tube, which is</p><p>mounted on the cockpit floor is supported at each end with bronze bushings. These bushings</p><p>have a grease fitting installed so that grease may be applied as necessary. As these bronze</p><p>bushings wear, fore and aft slack may develop which can be removed by the addition of shims</p><p>made of .010 thick steel. These shims are added on the forward end of the torque tube. The stops</p><p>for the elevator control system are located on each side of the elevator horn. The aileron control</p><p>stops are welded to the floor structure at the forward end of the torque tube.</p><p>Description Page 10 Air Tractor, Inc</p><p>April 1, 1998 AT-401</p><p>Both the aileron stops and the elevator down stop employ neoprene washers which act as shock</p><p>absorbers for the system. The rudder stops are located at the rudder horn. The rudder controls</p><p>consist of large stainless cables. There is a spring interconnect between the rudder and the aileron</p><p>system which allows banking the aircraft with rudder application alone.</p><p>BRAKE SYSTEM</p><p>The brake master cylinders are Cleveland p/n 10-23F. Brake fluid is the conventional red</p><p>petroleum-base Mil-H-5606A fluid. The brake fluid reservoir is a Volkswagen p/n 113611301L</p><p>and is mounted beneath the instrument panel with the cap protruding through the top of the</p><p>panel for easy access. The parking brake valve is a Scott p/n 4500A-2. Stratoflex hoses are used</p><p>from the pressure side of the master cylinder to the parking brake valve and stainless steel lines</p><p>are routed from the valve to the bulkhead fitting next to the main landing gear. A high-pressure</p><p>Stratoflex hose connects the bulkhead fitting to the wheel cylinders.</p><p>DISPERSAL SYSTEM</p><p>The standard spray system includes two-inch stainless plumbing and streamlined extruded</p><p>aluminum booms. Thirty-eight nozzles are incorporated although the boom is drilled and tapped</p><p>for an additional 36 nozzles if desired. Quick-couplers are used in order to remove the booms and</p><p>pump from the aircraft in minutes. The spray pump is an Agrinautics p/n 65219 two-inch</p><p>capacity pump. The fan is a Micronair p/n AT-4300 five blade adjustable fan. The control valve is</p><p>a Transland p/n 20384 and the strainer is an Air Tractor p/n 80392-10. The bottom-load valve is</p><p>a Transland two and a half inch p/n 20395.</p><p>All hoses used in the spray system have a special lining which is impervious to nearly all</p><p>chemicals. The hoses are double clamped at all connections with stainless worm-drive clamps. All</p><p>plumbing parts have beaded ends to provide secure hose attachments.</p><p>However, high line pressures and water-hammer effects can blow fittings loose and it is a</p><p>good practice to wire all Quick-couplers together with a loop or two of safety wire. In addition,</p><p>stainless wire is used to safety the plumbing on the discharge side of the pump to the top of the</p><p>pump.</p><p>Spray nozzles used are Spraying Systems Inc. p/n 4666 diaphram check valve, p/n 1/8</p><p>QJJ-VI Quick Coupling Body, p/n QU-4010 spray tip. The aircraft is equipped with -4010 spray</p><p>tips which is for medium volume applications. For high volume spraying QU-4025 tips should be</p><p>installed. If this still does not provide the required flow rates the fan should be changed to an</p><p>Agrinautics p/n 66450 six-blade adjustable-pitch fan. With this fan set in low pitch and with 81</p><p>nozzles installed with QU-4025 tips, flow rates on the order of 165 gallons per minute are possible</p><p>at pressures of approximately 40 psi.</p><p>The boom pressure gauge is glycerin-filled for long gauge life and to prevent needle</p><p>fluctuations. Copper tubing is used to connect the boom pressure gauge to a bulkhead fitting in</p><p>the lower fuselage skin. From the bulkhead fitting to the center boom assembly a Stratoflex hose</p><p>is used.</p><p>Fan brake lever is an industrial over-center type lever which has considerable leverage so</p><p>that the fan can be stopped instantly. The brake cable tension can be adjusted in the cockpit by</p><p>rotating the brake lever handle.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Description Page 11Description Page 11Description Page 11Description Page 11Description Page 11</p><p>AT-401AT-401AT-401AT-401AT-401 April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998</p><p>Description Page 12 Air Tractor, Inc</p><p>April 1, 1998 AT-401</p><p>Micronair rotary atomizers may be installed if desired. The factory supplies a special boom</p><p>for 8 atomizers.</p><p>For dry materials a Transland p/n 22358 extra high volume spreader is used. When the</p><p>spreader is installed the strainer should be rotated as required for clearance. For rapid</p><p>changeover from spray to dry materials remove only the pump and booms. For extended fertilizer</p><p>application it is suggested that the center boom assembly and control valve be removed to</p><p>prevent fertilizer from getting into the valve assembly. This can be accomplished in only a few</p><p>minutes by removing the stainless “T” pins which support the center boom assembly and</p><p>removing the two bolts that attach the valve to the stainless bracket.</p><p>The Air Tractor features a near leak-proof hopper lid which allows full liquid loads to be</p><p>carried. The leak-proof feature is made possible by a sturdy over-center latch assembly and a</p><p>curved hopper top which allows the hopper lid to be pulled solidly into space. Medium density</p><p>nitrile 3/8 x 1' wide is used for a hopper lid gasket.</p><p>The hopper vent tube is welded 3" diameter stainless tubing inside the hopper. A 3" stainless</p><p>ball is used to seal off the overboard vent when the liquid level reaches the top of the hopper. The</p><p>vent tube protruding from the lower fuselage skin is made of aluminum and can be rotated to</p><p>point forward to provide positive pressure in the hopper for dry material application. This slight</p><p>pressurization in the hopper requires a little less gate opening for a given poundage which reduces</p><p>the blockage effects of the door opening into the slipstream. When the vent tube is rotated to point</p><p>aft, a slight negative pressure is created inside the hopper which prevents any fumes from</p><p>escaping around the hopper lid gasket.</p><p>Optional dispersal equipment includes a 3-inch spray system which utilizes the Agrinautics</p><p>p/n 65715-1 3-inch pump, 3-inch plumbing to the pump, and 2 1/2-inch plumbing to the booms.</p><p>An optional spreader is the Transland 54401 NorCal Swathmaster which requires the p/n</p><p>24274 adapter box and the 25-inch gate box.</p><p>HOPPER RINSE SYSTEM</p><p>A hopper rinse tank is located in the fuselage and may be filled with tap water for hopper</p><p>rinse. To rinse the hopper after spray chemicals are expended turn the rinse switch ON for a</p><p>sufficient time for water to clean the hopper walls, then OFF.</p><p>The pump will empty the 18 gal. tank in approximately 1 1/2 minutes. Be sure to open the</p><p>drain valves during cold weather so that the system is not damaged by freezing. The drain valves</p><p>are located at the pump and at the check valve.</p><p>AIR TRACTOR, INC.AIR TRACTOR, INC.AIR TRACTOR, INC.AIR TRACTOR, INC.AIR TRACTOR, INC.</p><p>Olney, TexasOlney, TexasOlney, TexasOlney, TexasOlney, Texas</p><p>AT-401AT-401AT-401AT-401AT-401</p><p>TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS</p><p>OPERATION SECTIONOPERATION SECTIONOPERATION SECTIONOPERATION SECTIONOPERATION SECTION</p><p>Page No.Page No.Page No.Page No.Page No.</p><p>Preflight, Walk-Around Inspection 1</p><p>Safety Precautions Before Starting 2</p><p>Starting 2</p><p>Warm-up 3</p><p>Taxi 4</p><p>Before Take-Off 4</p><p>Take-Off (Normal) 4</p><p>Take-Off (Full Hopper Load and Short Strip) 5</p><p>Cruise</p><p>5</p><p>Agricultural Flying 5</p><p>Survey of field 5</p><p>Entering Field 6</p><p>Swath (Spraying) 6</p><p>Pull-Ups 6</p><p>Turns 6</p><p>Approach and Landing (Normal) 7</p><p>Landing (Cross-Wind) 7</p><p>Stopping the Engine 7</p><p>Loading the AT-401 7</p><p>Living With the Lines 8</p><p>PREFLIGHT, WALK-AROUND INSPECTIONPREFLIGHT, WALK-AROUND INSPECTIONPREFLIGHT, WALK-AROUND INSPECTIONPREFLIGHT, WALK-AROUND INSPECTIONPREFLIGHT, WALK-AROUND INSPECTION</p><p>Visual inspection of the exterior of your Air Tractor should become an important routine</p><p>procedure. A suggested path would be to start at the baggage door location and walk clockwise</p><p>around the aircraft.</p><p>The following items should be checked:</p><p>1. See that the baggage door is closed and fastened.</p><p>2. Check boom and fittings for leaks.</p><p>Check mounting brackets.</p><p>3. Lift up on trailing edge of flap to see that it is secure.</p><p>4. Move left-hand aileron briskly up and down to check for looseness of hinges.</p><p>Check for security of counterweight.</p><p>5. Inspect tip and leading edge for damage.</p><p>6. Inspect fuel vent tube.</p><p>7. Lift cover from pitot tube and inspect.</p><p>8. Remove left-hand fuel cap and visually check fuel level.</p><p>9. Drain left wing fuel sump, drain header tank sump, drain wobble pump sump.</p><p>10. Check spray plumbing and valve for leaks or loose connections.</p><p>11. Inspect left-hand gear leg connection at fuselage.</p><p>12. Inspect prop blades for nicks or cracks.</p><p>13. Inspect governor for security of controls and oil leaks around base.</p><p>14. Check cowling for security or any unfastened Camlocs.</p><p>15. Inspect cylinders for leaks around head and barrel connections, and for cracks around</p><p>spark plug bushings.</p><p>16. Inspect exhaust manifold for cracks or chafing on heat muff.</p><p>17. Inspect right-hand gear leg at fuselage connection.</p><p>Inspect both wheels and brakes and check tire inflation.</p><p>18. Remove right-hand fuel cap and visually check fuel level.</p><p>19. Drain right-hand wing fuel sump.</p><p>20. Inspect right-wing leading edge and tip for damage.</p><p>21. Inspect right-wing wing tank vent.</p><p>22. Inspect right-hand aileron same as left hand.</p><p>23. Check right-hand boom for leaks and security.</p><p>24. Check right-hand flap by lifting up on trailing edge.</p><p>25. Inspect fuselage skins for any unfastened Camlocs.</p><p>26. Inspect right-hand stabilizer and struts.</p><p>Test for security by lifting up on stabilizer leading edge.</p><p>27. Check forward end of tail spring for security.</p><p>28. Inspect right-hand elevator and move up and down to check security.</p><p>29. Check right-hand and left-hand elevator trim tabs for security and check linkage.</p><p>30. Inspect rudder on both sides and move from stop to stop to check security and cable</p><p>attachment.</p><p>31. Inspect tail spring attachment to fuselage.</p><p>Inspect tail wheel fork housing and attachment to spring.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Operations Page 1Operations Page 1Operations Page 1Operations Page 1Operations Page 1</p><p>AT-401AT-401AT-401AT-401AT-401 September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989</p><p>Check for proper tail wheel inflation.</p><p>Check for broken centering springs.</p><p>Check tail wheel lock by lifting plunger by hand.</p><p>32. Check left-hand elevator by moving up and down to test for security.</p><p>33. Inspect left-hand stabilizer and strut and check for security by lifting up on stabilizer</p><p>leading edge.</p><p>34. Inspect for loose skins or unfastened Camlocs on left-hand side of aircraft.</p><p>35. Open hopper lid, check inside hopper and check lid gasket.</p><p>Close hopper lid and secure latch.</p><p>36. Open oil tank access door and check oil level. Must be at least 5 gal. (See item 40).</p><p>37. Make sure switch is off, throttle and mixture levers full back, parking brake is on. Then</p><p>pull prop through by hand several revolutions to be sure all oil that may have collected in</p><p>lower cylinders is removed. Use caution while pulling the prop through.</p><p>38. Be sure tie-down ropes have been untied and wheel chocks removed.</p><p>39. Check ground under propeller for loose rocks or material that could damage propeller</p><p>blades when starting. Check behind aircraft to see that path is clear.</p><p>40. Before top-off with oil, start engine and run for a few minutes to allow oil to be pumped</p><p>back into tank.</p><p>SAFETY PRECAUTIONS BEFORE STARTINGSAFETY PRECAUTIONS BEFORE STARTINGSAFETY PRECAUTIONS BEFORE STARTINGSAFETY PRECAUTIONS BEFORE STARTINGSAFETY PRECAUTIONS BEFORE STARTING</p><p>1. Test toe brakes and set parking brake.</p><p>2. Fasten seat belt and harness.</p><p>3. Set altimeter.</p><p>4. Check rudder pedal position for a comfortable setting.</p><p>5. Position trim lever in green arc.</p><p>6. Move all flight controls through the normal operating range and check for unusual noises.</p><p>7. Turn on master switch.</p><p>Check fuel quantity in each tank on fuel receiver.</p><p>8. Actuate flaps to full range of travel. With flaps in fully lowered position the flap markings</p><p>should align perfectly with tail trailing edge. If flap down travel has exceeded this mark do</p><p>not fly the aircraft as the flap actuator down micro-switch could be malfunctioning.</p><p>During flap cycle listen for any unusual rubbing noises.</p><p>9. Check voltage on voltmeter. Turn off master switch and close right-hand canopy door.</p><p>STARTINGSTARTINGSTARTINGSTARTINGSTARTING</p><p>Before the engine is started, the propeller should be pulled through by hand at least 2</p><p>revolutions with the ignition switch off and the throttle and mixture levers full back, to prevent oil</p><p>in the lower cylinders from causing a hydraulic lock. Use caution when pulling prop through.</p><p>1. Turn fuel valve to ON position.</p><p>2. Place mixture control in the FULL RICH position (full forward).</p><p>Place the propeller control in LOW RPM (full aft). This prevents momentary loss of oil</p><p>pressure in filling propeller cylinder.</p><p>Operations Page 2Operations Page 2Operations Page 2Operations Page 2Operations Page 2 Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.</p><p>September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989 AT-401AT-401AT-401AT-401AT-401</p><p>3. Place carburetor heat in OFF position.</p><p>4. Set the brakes.</p><p>5. When the engine is cold, prime six to eight quick strokes while stroking the wobble pump</p><p>with the left hand. This is required to fill the primer.</p><p>6. Move throttle through full range of travel and back once or twice while stroking wobble</p><p>pump. Then position throttle 1/4 to 1/2 inch from aft stop.</p><p>7. Turn battery switch and alternator switch to ON.</p><p>8. Shout “CLEAR PROP” and wait for answer if anyone is present.</p><p>9. Place left hand on throttle lever and with right hand turn ignition switch to START. As</p><p>soon as engine starts, turn switch back to BOTH.</p><p>10. Position throttle to provide about 600 RPM and monitor oil pressure and fuel pressure. Oil</p><p>pressure should not exceed 100 psi and if engine is cold, reduce RPM as required to keep</p><p>oil pressure down. Fuel pressure should be 3 to 6 psi. If no oil pressure is observed within</p><p>15 seconds stop engine.</p><p>11. After starting move prop lever to full forward position.</p><p>12. If engine does not start immediately, do not keep starter engaged for more than 20</p><p>seconds at a time. Allow at least 3 minutes between starts. If engine has been overprimed,</p><p>open throttle completely and when engine starts, retard throttle rapidly to idle position. If</p><p>priming has not been sufficient, repeat starting procedure.</p><p>13. If battery is dead a 24 volt battery cart should be used with heavy duty jumper cables</p><p>attached to the correct battery terminals. After starting, leave the jumper cables attached</p><p>long enough for the battery to receive sufficient charge to close the solenoid on the battery</p><p>plate.</p><p>14. If battery is dead and no battery cart is available, the engine can be started by hand</p><p>swinging the propeller rapidly, providing the person is experienced with this method. If</p><p>hand swinging the propeller, the propeller should be pulled through with practice swings</p><p>several revolutions with the switch OFF. When “Contact” has been called by the person</p><p>doing the</p><p>swinging, and answered by the pilot, the pilot turns the ignition switch to BOTH</p><p>and the prop is pulled through rapidly, using extreme care to stay clear of the propeller</p><p>arc. If the prop stops in a position that is not desirable for anther attempt at swinging, the</p><p>person doing the swinging should call “OFF”, and only when answered by the pilot after</p><p>turning the ignition to “OFF”, should the prop be touched again.</p><p>WARM UPWARM UPWARM UPWARM UPWARM UP</p><p>The warm-up period is especially critical for the R1340 as the blower turns ten times the</p><p>crankshaft speed and the blower bearings will not be properly lubricated if engine RPM is</p><p>increased before the oil has a chance to warm up and reach a viscosity that will allow it to reach</p><p>the close fit of the blower bearings.</p><p>1. Allow engine to idle at 600 RPM or less for at least one full minute, and until oil pressure</p><p>is no more than 100 psi.</p><p>2. If oil pressure will stay below 100 psi, advance throttle to 700 RPM and run for one or</p><p>more minutes, depending on OAT.</p><p>3. Continue warm-up by advancing throttle in small stages up to 900 RPM, keeping oil</p><p>pressure below 100 psi.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Operations Page 3Operations Page 3Operations Page 3Operations Page 3Operations Page 3</p><p>AT-401AT-401AT-401AT-401AT-401 May 2, 1994May 2, 1994May 2, 1994May 2, 1994May 2, 1994</p><p>4. When oil temperature has reached 107°F (start of green arc) and pressure is 100 psi or</p><p>less, you are ready to taxi.</p><p>5. In all periods of warm-up, select an RPM that is smooth, so that loads on the ring cowl</p><p>attach lugs due to the engine shake are minimized.</p><p>TAXITAXITAXITAXITAXI</p><p>Whenever possible leave the tail wheel locked during taxi as this will minimize the need for</p><p>brakes. Small changes in direction can be made with the use of rudder and power. For sharp</p><p>turns on the ground unlock the tail wheel by pushing the stick full forward and use a little brake</p><p>along with powers. Since the brake forces on the AT-401 are light and effective be careful not to</p><p>ride the brakes during taxi since this will overheat the brake disc and cause excessive wear.</p><p>BEFORE TAKE-OFFBEFORE TAKE-OFFBEFORE TAKE-OFFBEFORE TAKE-OFFBEFORE TAKE-OFF</p><p>1. Recheck free and correct movements of flight controls.</p><p>2. If spray equipment is installed, fan brake control should be in “ON” position.</p><p>3. Re-check engine instruments and fuel quantity gauge.</p><p>4. Check trim lever for proper position. With empty aircraft, trim lever should be in the green</p><p>band. With a full hopper load, the trim lever should be slightly aft of the green band.</p><p>5. Close canopy door and check latches.</p><p>6. Be sure aircraft is positioned on a spot that is clear of small rocks that will damage</p><p>propeller.</p><p>7. Check mags by advancing throttle until manifold pressure is equal to field barometric</p><p>pressure. Normal mag drop is 50 to 70 RPM and should not exceed 100 RPM.</p><p>8. At 1900 RPM move the propeller control to High Pitch (Low RPM). A substantial drop in</p><p>RPM indicates satisfactory governor operation. Return prop control to full fwd. position</p><p>(High RPM).</p><p>9. Check the carburetor heat at 1900 RPM. A noticeable momentary drop in RPM with heat</p><p>full on indicates satisfactory operation.</p><p>10. If the engine accelerates smoothly and the oil pressure remains steady between 70 and 90</p><p>psi and the oil temperature is at least 107°F, the engine is warm enough for take-off.</p><p>TAKE-OFF (NORMAL)TAKE-OFF (NORMAL)TAKE-OFF (NORMAL)TAKE-OFF (NORMAL)TAKE-OFF (NORMAL)</p><p>1. Taxi forward with stick back until tail wheel lock pin is felt to engage.</p><p>2. Flap should be in retracted position, mixture FULL RICH, prop HIGH RPM.</p><p>3. With brakes set and stick full back advance throttle to approximately 1400 RPM.</p><p>4. Release brakes and as aircraft moves forward gradually advance throttle to provide a</p><p>smooth and continuous acceleration of the engine.</p><p>5. Allow the tail to come up and make a conventional take-off. As throttle is advanced make</p><p>sure manifold and RPM limits are not exceeded (36 inches and 2250 RPM for 5 minutes).</p><p>6. Best rate of climb speed for empty AT-401 is between 85 and 90 mph. For a heavy load</p><p>best rate of climb speed is between 95 and 100 mph.</p><p>7. Adjust trim lever for climb and set power at max. continuous rating (2200 RPM, 34.0"</p><p>Operations Page 4Operations Page 4Operations Page 4Operations Page 4Operations Page 4 Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.</p><p>May 2, 1994May 2, 1994May 2, 1994May 2, 1994May 2, 1994 AT-401AT-401AT-401AT-401AT-401</p><p>manifold pressure) or less if desired. For an empty AT-401, a good climb setting is 2100</p><p>RPM and 30 inches M.P.</p><p>TAKE-OFF (FULL HOPPER LOAD AND SHORT STRIP)TAKE-OFF (FULL HOPPER LOAD AND SHORT STRIP)TAKE-OFF (FULL HOPPER LOAD AND SHORT STRIP)TAKE-OFF (FULL HOPPER LOAD AND SHORT STRIP)TAKE-OFF (FULL HOPPER LOAD AND SHORT STRIP)</p><p>Use same procedure as for normal take-off except as follows:</p><p>1. Lower flaps to 10° position (first mark).</p><p>2. With a full hopper load apply full power before the brakes are released.</p><p>3. After breaking ground do not retract the flaps until at least 100 mph is reached.</p><p>CRUISECRUISECRUISECRUISECRUISE</p><p>Any amount of power up to maximum continuous ratings may be used for cruise. However,</p><p>avoid low RPM and high manifold pressure settings.</p><p>For an empty AT-401 with the pump removed for long ferry flights, an economy cruise</p><p>setting of 1900 RPM and 23.0 inches will provide an indicated air speed approximately 117 mph</p><p>at 8,000 ft. Fuel consumption at this setting is approximately 28 gallons per hour.</p><p>Other power settings that would be acceptable are as follows:</p><p>RPMRPMRPMRPMRPM Manifold PressureManifold PressureManifold PressureManifold PressureManifold Pressure Indicated AirspeedIndicated AirspeedIndicated AirspeedIndicated AirspeedIndicated Airspeed AltitudeAltitudeAltitudeAltitudeAltitude</p><p>1900 24.0 inches 120 mph 8,000 ft.</p><p>1900 25.0 inches 124 mph 8,000 ft.</p><p>2000 26.0 inches 130 mph 8,000 ft.</p><p>With the spray pump installed, a reduction in airspeed of approximately 2 mph will be</p><p>noted.</p><p>The R1340 engine on the AT-401 can be leaned at any altitude without detrimental effects</p><p>due to the lack of tightly enclosed cowling. Leaning will usually improve engine performance and</p><p>is recommended except when take-off power is used.</p><p>AGRICULTURAL FLYINGAGRICULTURAL FLYINGAGRICULTURAL FLYINGAGRICULTURAL FLYINGAGRICULTURAL FLYING</p><p>Since agricultural flying is extremely varied, it is not practical to recommend operating</p><p>procedures which in many cases would not fit a particular operation. However the procedures</p><p>outlined in this section are general and may be followed if they apply.</p><p>Survey of field: (Also see LIVING WITH THE LINES)Survey of field: (Also see LIVING WITH THE LINES)Survey of field: (Also see LIVING WITH THE LINES)Survey of field: (Also see LIVING WITH THE LINES)Survey of field: (Also see LIVING WITH THE LINES)</p><p>1. Before entering the field to be treated, fly around the entire perimeter at least once to</p><p>firmly establish the location of wires, standpipes, or other obstacles.</p><p>2. Determine direction field will be flown and check position of flagmen if used.</p><p>3. Check surrounding area on downwind side for possible drift damage.</p><p>4. Make note of houses or areas to avoid during turning.</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Operations Page 5Operations Page 5Operations Page 5Operations Page 5Operations Page 5</p><p>AT-401AT-401AT-401AT-401AT-401 September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989</p><p>Entering Field:Entering Field:Entering Field:Entering Field:Entering Field:</p><p>1. If practical, make first pass into the wind so that two passes will be made before the first</p><p>downwind turn is required. Avoid making first pass into the sun, however.</p><p>2. If obstructions border the field reduce speed slightly and make a high approach. When</p><p>obstruction is near enough, nose down smoothly to angle which will</p><p>clear obstruction and</p><p>apply power to prevent high-speed stall on roundout. Avoid flying just above obstruction</p><p>height and abruptly pitching over.</p><p>Swath (Spraying):Swath (Spraying):Swath (Spraying):Swath (Spraying):Swath (Spraying):</p><p>1. For a full load on a hot day set prop at 2150 RPM and manifold pressure at 30" or less,</p><p>depending on how well the aircraft is performing.</p><p>2. Spray runs may be made at 130 to 135 mph when the aircraft is heavy, which will provide</p><p>good penetration as well as adequate speed for pull-ups and turns.</p><p>3. As load diminishes, reduce RPM by 50 RPM increments so that as hopper nears empty,</p><p>RPM is 2,000. From 2,000 to 2150 RPM is the smoothest setting for the AT-401 due to the</p><p>engine mount design and engine vibration characteristics and therefore this should be the</p><p>normal working range.</p><p>4. Reduce manifold pressure as load diminishes to avoid excessive speed over the crop,</p><p>which reduces penetration. Spray speeds of 120 to 125 mph are normal as the hopper</p><p>nears empty.</p><p>5. The operator should select a speed which feels comfortable and best fits his particular</p><p>operation. In gusty air always use 5 to 10 mph more speed.</p><p>Pull-Ups:Pull-Ups:Pull-Ups:Pull-Ups:Pull-Ups:</p><p>1. Prior to pull-up apply additional power smoothly.</p><p>2. Abrupt pull-ups should be avoided since excessive speed is lost which reduces turn</p><p>performance.</p><p>3. When making pull-ups over wires avoid starting bank too soon.</p><p>Turns:Turns:Turns:Turns:Turns:</p><p>1. The previous training and experience will influence the operator flying the AT-401B. All</p><p>conventional types of turns may be performed in the AT-401B.</p><p>2. Flaps may be used as a turning aid providing small deflections are used (5 to 8 degrees).</p><p>The usual method for using flaps is to make the pull-up and initial bank with flaps</p><p>retracted. As the aircraft is being banked to turn back into the field touch the flap switch</p><p>briefly and let off a little back pressure on the stick, as the flaps cause a slight pitch up</p><p>tendency. Continue the turn, and as you line up for your pass, retract the flaps.</p><p>3. Make coordinated turns. Use the slip indicator as a means of determining whether or not</p><p>you are carrying bottom rudder. The AT-401B has excellent stall characteristics and if the</p><p>aircraft is inadvertently placed in an impending stall situation, it is only necessary to relax</p><p>some back pressure on the stick to make recovery, and little altitude is lost, providing the</p><p>turn is coordinated. A stall from a skidding turn will result in the nose dropping sharply</p><p>Operations Page 6Operations Page 6Operations Page 6Operations Page 6Operations Page 6 Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.</p><p>April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998 AT-401AT-401AT-401AT-401AT-401</p><p>with a significant loss of altitude.</p><p>4. In addition to being hazardous, a skidding turn can transfer fuel from one tank to</p><p>another, which will result in engine stoppage if one tank runs dry. Monitor the fuel level</p><p>in each tank when the fuel level reaches 1/2 tank, and leave the selector switch on the</p><p>low tank. Fuel transfer can occur when flying a racetrack pattern if the turns are not</p><p>coordinated.</p><p>APPROACH AND LANDING (NORMAL)APPROACH AND LANDING (NORMAL)APPROACH AND LANDING (NORMAL)APPROACH AND LANDING (NORMAL)APPROACH AND LANDING (NORMAL)</p><p>1. Set mixture control FULL RICH.</p><p>2. Reduce power slightly and move prop control full forward (High RPM).</p><p>3. Pull Carb. heat control full on if icing conditions exist.</p><p>4. Close throttle and establish glide at 85-90 mph (flaps up) or 75-80 mph (flaps down).</p><p>These figures for empty aircraft. The engine should be cleared occasionally by opening</p><p>throttle.</p><p>5. During landing roll, steer the aircraft with rudder. Brakes are for stopping or turning off</p><p>the runway. Avoid heavy braking. The AT-401 is a slow landing aircraft and it is poor pilot</p><p>technique to land so close to your loading rig that heavy braking is required.</p><p>LANDING (CROSS-WIND)LANDING (CROSS-WIND)LANDING (CROSS-WIND)LANDING (CROSS-WIND)LANDING (CROSS-WIND)</p><p>1. Establish proper crab angle to line up with runway.</p><p>2. Leave flaps retracted unless strip is very short and cross-wind does not exceed 15 mph.</p><p>3. During final stages of flare-out apply necessary rudder to straighten aircraft with runway.</p><p>In strong crosswinds, it will be necessary to lower the up-wind wing.</p><p>4. Touch down should be in tail-low attitude and on up-wind wheel. Allow downwind wheel</p><p>to touch, then tail wheel.</p><p>5. Remain alert during roll-out. Steer with rudder and use brakes only if necessary.</p><p>STOPPING THE ENGINE:STOPPING THE ENGINE:STOPPING THE ENGINE:STOPPING THE ENGINE:STOPPING THE ENGINE:</p><p>1. Idle for at least one minute to cool engine.</p><p>2. Run up engine to 1500 RPM and shift propeller into high pitch (Low RPM) and reduce</p><p>speed to idle. (Not required on aircraft with Hydromatic propeller.)</p><p>3. Move mixture control to FULL LEAN position and when engine cuts, move throttle forward</p><p>slowly.</p><p>4. Continue opening the throttle slowly after the engine starts to cut. When engine stops,</p><p>turn off ignition switch, battery switch, alternator switch.</p><p>5. Set brakes and control lock.</p><p>LOADING THE AT-401:LOADING THE AT-401:LOADING THE AT-401:LOADING THE AT-401:LOADING THE AT-401:</p><p>Under the provisions of CAM8.10-4 (b) “Maximum capacities should be selected by the</p><p>applicant and demonstrated in the flight check in accordance with section 8.10-3 (e). (1.) These</p><p>maximum capacities for hoppers or tanks should be listed on placards on or adjacent to the</p><p>appropriate filler covers.”</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Operations Page 7Operations Page 7Operations Page 7Operations Page 7Operations Page 7</p><p>AT-401AT-401AT-401AT-401AT-401 April 1, 1998April 1, 1998April 1, 1998April 1, 1998April 1, 1998</p><p>LIVING WITH THE LINESLIVING WITH THE LINESLIVING WITH THE LINESLIVING WITH THE LINESLIVING WITH THE LINES</p><p>By J.J. Snyder</p><p>(Re-print by permission of ON THE DECK magazine)</p><p>A Little BackgroundA Little BackgroundA Little BackgroundA Little BackgroundA Little Background</p><p>Over the past years I have seen several sets of statistics dealing with wirestrikes by agricul-</p><p>tural aircraft, and without exception these columns of numbers, while no doubt serving some</p><p>useful purpose, are altogether lacking in specific information or practical recommendations to</p><p>pilots for the avoidance of these hazardous objects which are so much a part of their working</p><p>environment.</p><p>As an agricultural pilot for twenty years, I have some experience in avoiding powerlines, and</p><p>somewhat more experience than I would wish in striking them. I have learned a great deal about</p><p>airplanes and wires over the past seasons, and the acquisition of this knowledge has sometimes</p><p>been accompanied by destruction of property and hazards to other persons, while helping to</p><p>furnish those moments of sheer terror which relieve the hours of boredom in the cockpit.</p><p>There is some verbal exchange among pilots on wirestrike hazards, but because each one</p><p>usually assumes the other is in possession of the same knowledge as himself, and since there is a</p><p>certain reluctance on everyone’s part to lecture, some of those who need it the most either never</p><p>get the word or receive it too late.</p><p>Because of the lack of written data on this subject, I feel compelled to put on paper some of</p><p>the ideas and procedures which I have found to be helpful in the avoidance of these obstacles to</p><p>flight, in the hope that they may benefit others.</p><p>The more time one spends in any occupation, the more one learns about it, and I realize</p><p>that many seasoned pilots will already have this information. (They may quite possibly be aware</p><p>of more and better ways of staying out of trouble, and I sincerely hope that those who have such</p><p>knowledge will also make it available.) As for this text, it is mainly directed at those aviators with</p><p>rather limited experience who, somewhere in their training, may</p><p>have missed a vital bit of</p><p>information which could be quite important to their future.</p><p>Check Fields YourselfCheck Fields YourselfCheck Fields YourselfCheck Fields YourselfCheck Fields Yourself</p><p>When assigned a field to treat, a pilot should inspect the field thoroughly from the air, even</p><p>if it is familiar to him from previous jobs. The responsibility for being aware of all obstructions</p><p>rests entirely with him, and should not be delegated to any ground personnel. There is a case on</p><p>record of a pilot trusting in a flagger’s word that a line was clear to go under, and subsequently</p><p>flying through a one-inch coaxial cable strung beneath the wires.</p><p>Pacific Gas & Electric has lately initiated a program using high visibility plastic markers,</p><p>which are distributed to operators in the hope that they will place these devices beneath power</p><p>lines as reminders to pilots of the existence of hazards. This utility’s aim to reduce the number of</p><p>accidents is commendable, but these objects are not being used by the majority of applicators</p><p>because of possible legal problems arising from their use, and since they require extra time and</p><p>labor to set up and move, their use is not compatible with a high acre-per-hour production rate.</p><p>Before undertaking to fly a field, one should circle it several times and note the position of</p><p>all wires, poles and other obstacles. If a pilot takes enough time to make a complete inspection,</p><p>Operations Page 8Operations Page 8Operations Page 8Operations Page 8Operations Page 8 Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.</p><p>September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989 AT-401AT-401AT-401AT-401AT-401</p><p>he is not as likely to forget the placement of the wires as he might in a quick once-over flyby. If he</p><p>has treated the field previously he should look for changes in the position of the lines around</p><p>and/or across it, and the possible addition of horizontal guywires or telephone lines beneath the</p><p>electrical cables. He should also be alert for wires which are partially concealed by foliage in the</p><p>background, and poles which may be hidden in clumps of trees or bushes. Poles which are lower</p><p>or wider apart than usual should be noted, and their presence recalled on each pass.</p><p>Since electrical lines themselves are not highly visible objects under most conditions, the</p><p>placement of poles and their crossarms are very important clues in determining wire presence</p><p>and direction. Wires are always strung at a ninety degree angle to their crossarms. If a crossarm</p><p>is fastened to the pole at a thirty or forty-five degree angle to the field boundary, it is safe to</p><p>assume that its wire will cross at an angle more or less than ninety degrees to the path of flight,</p><p>and the pullup must be started earlier than usual if electing to fly over it. These angled wires in</p><p>corners of fields can be quite hard to detect, and although they do not exist in great numbers in</p><p>most areas, their potential for harm makes it imperative that they be located and avoided.</p><p>A pilot must remember that wherever a pole line ends, it is always anchored by a guy wire,</p><p>which is a steel or aluminum cable stretched from pole top to ground at approximately a forty-five</p><p>degree angle, its purpose being to keep the lines taut and the poles erect. These cables are most</p><p>dangerous to aircraft while a first or last pass parallel to the pole line is being made, and the guy</p><p>wire from an adjoining pole line at an angle to the first juts out into the flight path. They can be</p><p>spotted rather easily from the air in most cases, but their location must be kept constantly in</p><p>mind. In some fields, their point of anchorage in the ground will show as a clump of plants or</p><p>high weeds where the cultivator made a detour to miss the cable.</p><p>Plan Your RunsPlan Your RunsPlan Your RunsPlan Your RunsPlan Your Runs</p><p>When the field inspection has been made, and all obstructions identified and committed to</p><p>memory, the pilot must decide whether to make his passes over or under the wires surrounding</p><p>the treatment area and/or running through it. His decision should be the product of a reasoned</p><p>judgement, based on experience and the nature of the lines.</p><p>As previously mentioned, wires themselves are not sufficiently visible under all conditions to</p><p>be useful in gauging one’s distance from them, and if he elects to enter or leave the field over the</p><p>lines, the pilot should determine his obstacle clearance altitude by the pole height alone, not start</p><p>letdowns or pullups by reference to the wires between them. A measure of extra altitude over the</p><p>poles on entry and an earlier pullup at the end of the pass is recommended if the poles are higher</p><p>than usual or there is a lack of good visibility around the field. The practice of leaving the ends of</p><p>the field unsprayed and later covering them with several headland passes is encouraged, as it</p><p>gives a margin of safety in climbs and letdowns while assuring full coverage of the crop. No turns</p><p>should be initiated during the pullup out of the field until a safe height above the poles is</p><p>reached.</p><p>As a general rule, subject to individual choice, when the poles are tall and the wires stretch</p><p>along their upper portion with negligible droop, there are no lower lines strung beneath, they are</p><p>not located along a busy highway, and no other obstructions such as fences, irrigation pipes or</p><p>farm machinery exist beneath the lines, it is quite safe to enter and/or leave the field flying under</p><p>the wires. In some ways this method is less hazardous than going over the lines, which then</p><p>disappear under the nose and are lost to view at a time when it is quite desirable for them to be</p><p>Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc.Air Tractor, Inc. Operations Page 9Operations Page 9Operations Page 9Operations Page 9Operations Page 9</p><p>AT-401AT-401AT-401AT-401AT-401 September 15, 1989September 15, 1989September 15, 1989September 15, 1989September 15, 1989</p><p>in sight. It also does away with the flareout in the field after descent over the wires, which can be</p><p>an occasion of some danger when coupled with a heavy load, high temperatures, or a tall, dense</p><p>crop.</p><p>The pass under the lines should begin at a far enough distance away from the field</p><p>boundary to be able to glance up quickly at the approaching bay of wires so as to determine that</p><p>there are no lower lines present, and if crossing a road or highway, that no traffic exists for one</p><p>quarter mile or more on either side of the pass. If this view is obstructed, it is wise to approach</p><p>over the wires rather than take a chance of collision with a ground vehicle. Under the lines, the</p><p>aircraft should be in level flight, since the chance of wire contact increases in a climb, dive, or</p><p>bank.</p><p>Flaggers must be instructed to move as soon as the airplane is lined up, and if they have</p><p>correctly, the pilot should not have to be concerned about their position, or need to take evasive</p><p>action to avoid hitting them. Flaggers who are consistently slow to move and respond to direc-</p><p>tions should be discharged for their own safety.</p><p>Never Assume AnythingNever Assume AnythingNever Assume AnythingNever Assume AnythingNever Assume Anything</p><p>When flying under wires, a pilot should not assume that, simply because one space between</p><p>poles is clear of low lines, they all are. On the last pass before going on to the next bay, he should</p><p>quickly glance up and down the pole for signs of lower lines or the very hazardous horizontal guy</p><p>wires, also known as deadmen. These are one half to three quarter inch steel or aluminum cable</p><p>stretched between two poles, and upon striking one an aircraft can easily be brought to a sudden</p><p>stop and dismantled.</p><p>Wire crossing the field inside its perimeter can be flown in a similar manner to those on the</p><p>boundaries, although one should keep their position in mind as they sometimes slip the memory</p><p>more easily than the outer lines. Pullups and letdowns</p>