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TPE331 Turboprop Engine Training Manual Honeywell National Flight Services Authorized Service CenterTPE331 Line Maintenance Training Manual FOREWORD 0-1 Ambient Conditions-How They Affect Engine Performance 1-42 CHAPTER 1 - Day Sea Level 1-42 -29°C Outside Air Temperature/Sea Level DESCRIPTION & OPERATION 1-1 (OAT/SL)-Exceed Hp Limit 1-44 OBJECTIVES 1-1 49°C OAT/SL-Temp Limited 1-46 HISTORY 1-2 High Altitude-Temperature Limited 1-48 DESCRIPTION 1-2 Air Density Power 1-50 Two-Stage Centrifugal Compressor 1-4 TROUBLESHOOTING 1-52 Combustion Chamber 1-6 Engine Parameters 1-52 Three-Stage Axial Turbine 1-8 Troubleshooting From the Cockpit Rotor Coupling and Air Seals 1-10 -Normal 1-54 Gas Generator 1-12 Scenario #1 1-56 Gear Reduction Section 1-14 Scenario #2 1-58 Clockwise Propeller Shaft Rotation 1-16 Scenario #3 1-60 Counterclockwise Rotating Prop 1-18 Scenario #4 1-62 AIRFLOW STATIONS 1-20 Scenario #5 1-64 Scenario #6 MODEL NUMBERS 1-22 1-66 Reverse High Check-Normal 1-68 TPE331 RATING VALUES-HORSEPOWER 1-24 Scenario #7 1-70 FLAT RATING 1-26 Scenario #8 1-72 FUEL CONSUMPTION 1-28 PERFORMANCE RATINGS OF TPE331 MODELS 1-30 CHAPTER 2- POWER CONVERSION-FREE 1-32 POWER MANAGEMENT 2-1 POWER CONVERSION-FIXED 1-34 OBJECTIVES 2-1 OPERATION 1-36 OVERVIEW 2-2 Constant Speed Advantage 1-36 CONTROLLING ENGINE OPERATING Constant Speed Theory 1-38 PARAMETERS 2-4 Power Limits 1-40 Cockpit Controls 2-4 Fuel/Prop Controls 2-6 Page 1 ppc prop pitch controlTPE331 Line Maintenance Training Manual BASIC POWER MANAGEMENT 2-8 CHAPTER 4-PROPELLER Engine Power Control 2-10 CONTROL SYSTEM 4-1 Engine RPM Control 2-12 OBJECTIVES 4-1 Prop Governing Mode 2-14 OVERVIEW AND COMPONENTS 4-2 Beta Mode 2-16 SINGLE ACTING PROPELLERS 4-6 Rigging 2-18 Beta Tube 4-6 BETA PRESSURE SWITCH MANIFOLD 4-10 UNFEATHER PUMP 4-12 CHAPTER 3 - 3-1 TYPICAL PROPELLER BLADE ANGLES 4-14 OPERATIONAL SEQUENCE PPC/MFV RELATIONSHIP 4-16 OBJECTIVES 3-1 OPERATING MODES 4-20 PRESTART 3-2 3-4 Propeller Governing Mode 4-20 CRANKING Beta Mode 4-20 LIGHT OFF 3-6 PROPELLER GOVERNOR 4-22 ACCELERATION 3-8 PROP GOVERNING MODE 4-26 CRITICAL SPEED RANGE 3-10 PROPELLER CONTROL SYSTEM 4-28 50/60% RPM 3-12 3-14 Propeller Governing Mode 4-28 ON SPEED PROPELLER PITCH CONTROL 4-32 Required Fuel 3-16 PITCH CONTROL OPERATION 4-34 PROP LOCKS RELEASE 3-18 Ground Idle to Reverse 4-34 TAXI 3-20 Reverse to Flight Idle 4-36 80% RPM 3-22 BETA MODE 4-38 MAX POWER-TAKEOFF 3-24 3-26 BETA Mode Operation 4-40 CRUISE BETA Mode-Full Reverse 4-44 APPROACH 3-28 Flight Idle-Ground 4-46 FLARE ON LANDING 3-30 Flight Operations-Flight Idle 4-50 REVERSE THRUST-BRAKING 3-32 NEGATIVE TORQUE AND NTS SYSTEM 4-54 TAXI 3-34 Torque Sensor Assembly 4-56 SHUTDOWN 3-36 PROPELLER CONTROL SYSTEM 4-58 Page 2TPE331 Line Maintenance Training Manual NTS Operation in Flight 4-58 Underspeed Governor Control 5-20 NTS Ground Check (Setup) 4-62 Manual Fuel Control 5-22 NTS Ground Check (Starter Energized) 4-64 PRESSURIZING VALVE 5-24 OUTPUT GEARBOX HOUSING AND MANUAL/AUTO START FUEL 5-26 PROPELLER SHAFT 4-66 Start Fuel Pressure Regulator -1/-2 5-28 Torque Load Assemblies and Fuel Pressure Regulator Assembly 5-30 NTS Valve 4-68 Start Fuel Pressure Regulator -5/-6 5-32 Preload and NTS Valve Operation 4-70 TORQUE/TEMPERATURE LIMITING NTS OPERATION IN FLIGHT 4-72 SYSTEM 5-34 Negative Torque System 4-76 Torque/Temperature Limiter Assembly NTS Maintenance Ground Check (Bypass Valve) 5-36 Functional Ground Check 4-78 FUEL SHUTOFF (SOLENOID) VALVE Procedure 4-78 WITH MANUAL OVERRIDE 5-38 FLOW DIVIDER 5-42 CHAPTER Primaries Only Solenoid FUEL SYSTEM 5-1 (Flow Divider Reset) 5-44 OBJECTIVES FUEL MANIFOLD AND NOZZLE 5-1 ASSEMBLIES AIRCRAFT FUEL SYSTEM 5-46 5-2 P.C. -6 ENGINES Engine Fuel System Components 5-46 P.C. thru -6 Fuel Manifold and Nozzle Assemblies 5-4 Engine Fuel System Components -10/-11 Engines 5-48 -10 thru -11 Fuel Manifold and Nozzle Assemblies 5-6 Engine Fuel System Components -10, -11, and -12 Engines 5-50 -10/-11 and All -12 5-8 Atomizer Body and Tip 5-52 P2/T2 SENSOR FUEL PUMP ASSEMBLY 5-54 5-10 T2 Pt2 Effects FUEL CONTROL UNIT 5-56 5-12 Tt2 Sensor Effects Metering and Bypass 5-12 5-58 Tt2 Bellows Failure Acceleration Control 5-60 5-16 Fuel Schedule Relationships 5-18 Page 3TPE331 Line Maintenance Training Manual FUEL CONTROL ADJUSTMENT APR SYSTEM USING FUEL LOCATIONS 5-62 ENRICHMENT 6-48 FUEL SYSTEM OPERATION 5-64 CHAPTER 7- CHAPTER 6 TORQUE INDICATION SYSTEM 7-1 TEMPERATURE INDICATION SYSTEM 6-1 OBJECTIVES 7-1 OBJECTIVES 6-1 OVERVIEW 7-2 TEMPERATURE INDICATION MINIMUM ALLOWABLE TAKE-OFF POWER 7-4 SYSTEM OVERVIEW 6-2 TORQUE INDICATOR 7-6 Basic Temperature Indication Circuit 6-8 GEARBOX RATIO 26:1 7-8 MAIN COMPONENTS 6-10 TORQUE SENSOR 7-10 EGT Harness Assembly 6-12 POSITIVE TORQUE INDICATING SYSTEM EGT Limits at Pressure Altitude and OAT 6-14 Positive and Negative Pressures ITT Harness Assembly 6-16 Torque Sensor Pilot Valve Position 7-14 ITT Limits at Pressure Altitude and OAT 6-18 Minimum to Maximum Allowable Temperature Compensator 6-20 Engine Power 7-16 Data Sheet Customer (DSC) 6-26 HYDRAULIC TORQUE SENSING SYSTEM 7-18 SINGLE RED LINE CONTROLLER 6-28 Torque Sensor Calibration 7-20 Maximum EGT Limit with SRL Customer Data Sheet (DSC) 7-22 Controller Off 6-32 Torque Compensator Assembly 7-24 Takeoff/Cruise Temperature Schedules for POSITIVE TORQUE SYSTEM 7-26 Engines 6-34 HYDRO-ELECTRIC TORQUE SENSING Takeoff/Cruise Temperature Schedules for AND LIMITING SYSTEM 7-28 Some TPE331-10 Engines 6-36 HYDRO-ELECTRIC TORQUE WATER METHANOL INJECTION SYSTEM 6-38 INDICATING SYSTEM 7-30 ITT & EGT Engines with Water/Methanol Typical Raw Torque Plot 7-32 Injection 6-44 Hydro-Electric System DSC 7-34 SRL/EGT Engines Variable Temperature Compensating Transducer 7-36 Adder with Water/Methanol Injection 6-46 Page 4TPE331 Line Maintenance Training Manual STRAIN GAGE TORQUE SENSING AND Oil Temperature Bulb 8-26 LIMITING SYSTEM 7-38 Magnetic Chip Detector 8-28 Strain Gage Torque Ring Transducer ACCESSORY MOUNTING PADS AND and Output Gear Reduction 7-40 LUBRICATION 8-30 Torque Ring (Transducer) 7-42 MAINTENANCE ACTIONS 8-32 Strain Gage (Strain Vs. Resistance) 7-44 Routine 8-32 Strain Gage Balanced Bridge 7-46 Corrective Maintenance 8-34 Strain Gage Stress Path 7-48 SOAP PROGRAM 8-36 Strain Gage Unbalanced Bridge 7-50 SOAP Kit 8-38 Strain Gage Sample DSC 7-52 SOAP Normal Increasing Trend 8-40 Strain Gage Torque Signal Conditioner 7-54 Sudden Increase in Metal Concentration 8-42 Bridge Crosscheck 7-58 Accidental Contamination 8-44 Problem Developing Increase 8-46 CHAPTER Filter Content Analysis 8-48 SOAP-PREVENTATIVE MAINTENANCE 8-50 LUBRICATION SYSTEM 8-1 OBJECTIVES 8-1 OVERVIEW/FLOW PATH 8-2 CHAPTER 9 - LUBE SYSTEM COMPONENTS 8-4 IGNITION SYSTEM 9-1 Oil Tank 8-6 OBJECTIVES 9-1 Air/Oil Separator 8-8 IGNITION SYSTEM 9-2 Gerotor Pumps 8-10 Pressure Pump/Main Scavenge Pump 8-12 CHAPTER 10 - Turbine Bearing Lubrication and Scavenge Pump 8-14 PNEUMATIC SYSTEM 10-1 Oil Vent Valve 8-16 OBJECTIVES 10-1 Oil Filter Assembly 8-18 PNEUMATIC SYSTEM OVERVIEW 10-2 Oil Filter Bypass Valve 8-20 ENGINE ANTI-ICE SYSTEM 10-4 Oil Pressure Regulator Valve 8-22 Anti-Ice Valve 10-6 Typical Oil Pressure Limits 8-24 Anti-Ice Operational Check 10-8 Page 5TPE331 Line Maintenance Training Manual BLEED AIR SYSTEM AND FCU 10-10 Fuel Manifold Purge System 10-10 P3 Signal to the Fuel Control 10-10 Airframe Systems 10-12 MAINTENANCE ACTIONS 10-14 CHAPTER 11- PUBLICATIONS 11-1 OBJECTIVES 11-1 PUBLICATION PRIORITY 11-2 ATA-100 FORMAT 11-4 ADDITIONAL LINE MAINTENANCE PUBLICATIONS 11-6 SERVICE MANUAL CONTENTS 11-8 INFORMATIONAL MATERIAL 11-16 CUSTOMER ENGINE MANUALS 11-18 ENGINE LOG BOOK 11-20 ENGINE CYCLE DEFINITION 11-22 ENGINE DATA PLATE 11-24 MICROFICHE FORMAT 11-26 ABBREVIATIONS AND ACRONYMS 12-1 GLOSSARY 12-3 Page 6TPE 331 Line Maintenance -Training Manual FOREWORD Official publications pertaining to operating proce- dures, limits, and capabilities of engines or their Training study guides are provided by AlliedSignal components are the responsibility of the airframe Aerospace Engines for the limited purpose of pre- manufacturer. The airframe manufacturer installs senting illustrations, and general the engine in its airframe, designs and/or selects information to students in support of a specific instruments, and flight tests the aircraft. The air- training course only. frame manufacturer determines how -- and under what limitations engines will be operated for all Information contained herein is intended only as a modes of taxi and flight. general description of operation to permit intelli- gent maintenance and systematic troubleshooting As an engine and engine component manufacturer of the subject system or components described support company, AlliedSignal Aerospace Engines herein. has the responsibility to alert airframe manufactur- ers that their aircraft manuals not permit operation It is not the intent of AlliedSignal Aerospace that beyond the limits of an engine's capabilities. Allied- any training publication be used as a supplement Signal may suggest and advise -- but not dictate to, or in lieu of, any official publication. Contents operational and maintenance practices it feels best herein are subject to change without notice. for the engine. Some aircraft manufacturers will The reader of this manual is reminded that all val- assimilate AlliedSignal manuals into their own ues of pressure, temperature, speed, power, etc. are publications while other manufacturers may simply chosen for their illustrative meaning only and are refer the owner/operator to AlliedSignal published manuals. not necessarily representative of true values. For actual values, the applicable maintenance manual must be consulted. Page 0-1TPE 331 Line Maintenance -Training Manual Official publications which apply to all engines and systems are listed below (with the highest ranking manual first): 1. Aircraft Flight Manual 2. Aircraft Maintenance Manual 3. Engine Maintenance Manual and Service Bulle- tins 4. Engine Overhaul Manual and Service Bulletins 5. Component Overhaul Manual and Service Bul- letins It was not accidental that this training manual is not included in the above list of publications: IN ALL INSTANCES, INFORMATION CON- TAINED IN OFFICIAL PUBLICATIONS SHALL GOVERN. COURSE GOAL To provide aircraft engine maintenance technicians the training required to service, inspect, operate, adjust and maintain the TPE331 engine. Page 0-2TPE331 Line Maintenance - Training Manual CHAPTER 1 DESCRIPTION & OPERATION OBJECTIVES After completing classroom discussion and related exer- cises, you should be able to: - Describe engine construction includinggas generator, gearbox, and accessory sections Identify engine airflow path and station numbering system Explain the interaction between engine power and gear reduction sections Identify engine models and performance ratings - Locate and identify external engine components - Discuss operational theory and engine instrumen- tation - Identify system malfunctions from given instrument indications Page 1-1TPE331 Line Maintenance - Training Manual HISTORY The first Garrett TPE331, rated at 575 shaft horsepower, was certified in January of 1965. The engine dry weight, minus propeller, of 335 pounds resulted in a horse- power to weight ratio of approximately 1.7 to new models were introduced with higher horsepower rat- ings, the basic frame size of the engine remained the same. With only a small weight increase, current engines have a horsepower to weight ratio of approximately 2.7 to 1. Depending upon the engine model and installation, shaft horsepower ratings vary from 575 to 1100. Since it's introduction in 1965, the TPE331 engine has been installed on more than 85 different aircraft models. Over 12 thousand engines have been shipped and the total accumulated fleet hours is well in excess of 80 mil- lion. DESCRIPTION The TPE331 turboprop engine uses: A two stage centrifugal compressor An annular combustion chamber A three stage axial turbine - Gearbox with integral compressor inle: Page 1-2Fixed - - 2 3 generator 12000 Page 1-5TPE331 Line Maintenance - Training Manual TWO-STAGE CENTRIFUGAL of approximately 7.6 pounds per second at approxi- COMPRESSOR mately 130 PSI on a standard day. The centrifugal com- pressor provides rugged and reliable construction characteristics making it less susceptible to foreign IDENTIFICATION AND LOCATION object damage (FOD) and erosion than axial flow com- The two-stage centrifugal (radial flow) compressor is pressors. located at the rear of the air inlet area. Each stage of compression consists of: MAINTENANCE TIP: - an impeller First stage impeller leading edges are all that can be - a diffuser accessed through the air inlet. Consult maintenance manual for repair limits of dents and nicks via blending. - a face shroud PURPOSE AND INTERFACE The compressor converts mechanical energy into pneu- matic energy. Inlet air is brought up to a higher pressure for use in combustion. OPERATION The centrifugal compressor develops pneumatic energy by drawing in ambient air at the hub of the first impeller and discharging it at a high velocity through a diffuser. The divergent vanes of the diffuser assembly convert the high velocity air to pressure by decreasing the velocity. The air is then directed to the second stage impeller where the process is repeated. FUNCTIONAL DESCRIPTION The two stages of compression in the TPE331 result in a nominal 10 to 1 compression ratio with a total air flow Page 1-4Impeller and Diffuser 1. : PageTPE331 Line Maintenance - Training Manual COMBUSTION CHAMBER slots at the outer edges to provide for some secondary air flow between the walls for In addition, later IDENTIFICATION AND LOCATION engine model combustor inner walls and curved aft shell of outer transition liners have TBC (thermal barrier coat- The combustion section of the TPE331 is a single annu- lar (ring-like) reverse flow chamber. It is located down- ing). This sprayed on (approximately .020 thick) stream of the second compressor, forming a ring around ceramic-based material will keep wall temperatures approximately 120°C cooler. the three-stage turbine in the plenum case. PURPOSE AND Within the combustion chamber, air is mixed with fuel and ignited, increasing the thermal energy of the airflow. OPERATION Air exiting the second stage diffuser is directed into the plenum chamber. From here, air is directed into the combustor itself where the pneumatic energy (air) is mixed with chemical energy (fuel) and ignited, convert- ing the pneumatic/chemical mixture to thermal energy. FUNCTIONAL DESCRIPTION Approximately 30% of the total amount of compressor discharge air (primary) is used for atomization of fuel and combustion. Some of the other 70% of the airflow (secondary) is directed through holes and louvers in the combustion chamber walls to center the flame cone and provide a cooling layer of air between the flame and the chamber itself. This high velocity thermal energy is then directed to the turbine section by the transition liners. The outer transition liner is double walled with holes or Page 1-63 Stage Axial Turbine Pressure Turbine Note PageTPE331 Line Maintenance - Training Manual Labyrinth seals are located between each compressor and turbine stage of the engine. When the engine is operating, centrifugal force plus heat causes rotating or "knife" seal growth. With this growth the knife edges operate in close tolerance to the stationary seal. The sta- tionary seal material will depend on engine model and Service Bulletin incorporation. Early models use a "felt metal spray" abradable material, while the newer seals are a honeycomb design. This close tolerance controls the leakage rate between stages to an acceptable value by providing a less desirable path for air to flow. This will directly affect engine operating efficiency. PageRTAF Gas Generator 41,730 RPM PageTPE331 Line Maintenance - Training Manual GEAR REDUCTION SECTION IDENTIFICATION AND LOCATION The gear reduction and shaft section, which contains the gearing to drive the propeller and engine driven accessories, is located in the nose (output), intermediate (diaphragm), and accessory cases at the forward end of the engine. PURPOSE AND INTERFACE The gearbox converts the high speed relatively low torque from the gas generator, to a lower speed with a higher torque value at the propeller (output) shaft. Accessories are driven through a series of parallel axis gears at the rear of the accessory case. OPERATION The gas generator is connected to the high speed pinion (within the gear section), which drives the bull gear/sun gear assembly. The sun-planet gear system then drives the ring gear and propeller shaft. A system of spur gears drives the accessories such as the propeller starter/generator, and hydraulic pump. The lubrication pumps, fuel pump, and fuel control assembly are driven by the gas generator through a separate gear train. The compressor inlet is integral with the accessory gearbox case. Page 1-14Son Gear Reduction Section coupling (ATAF). 21, High Speed EA) Pinion Gear Planetary Gear Assembly Sun/Bull Gear Assembly Propshaft Prop Accessory Gears Sun go throug FCU Ring Gear Output/Nose - Fuel Case Diaphragm Accessory Assembly Case Fuel Pomp 3 Ring R Gear Sun Fuel Governor. over speed Pump Take RPM Low RPM Page 1-15 Gear Cow HiTPE331 Line Maintenance - -Training Manual CLOCKWISE PROPELLER SHAFT ROTATION For clockwise propeller shaft rotation, the gearbox incorporates a fixed planetary gear carrier assem- bly. The bull gear/sun gear assembly drives the planet gears, which drives the rotating ring gear. The ring gear is attached to the propeller shaft with a splined hub. With the ring and propeller shaft rotating as one assembly this produces Clockwise rotation. The gearbox ratio is 20.865 to 1, with a 2000 RPM propeller speed at 100% engine speed. These "fast turn" models -6, and -10 conversions) usually drive a smaller, lighter weight three blade propeller. Page 1-16RTAF ok Clockwise Rotating Prop PLANETARY GEAR SUN GEAR PROP DIAPHRAGM SHAFT RING GEAR Page 1-17TPE331 Line Maintenance - Training Manual COUNTERCLOCKWISE ROTATING PROP Counter-clockwise propeller installations utilize a fixed ring gear. The bull gear/sun gear assembly drives the planet gears, which drives the rotating planet carrier and gear assembly. The planetary gears carrier assembly is attached to the propeller shaft with a splined coupling. With the planetary gear carrier assembly and the propel- ler shaft rotating as one assembly this produces Counter- clockwise rotation. The gearbox ratio is 26.229 to 1, with a 1591 RPM propeller speed at 100% engine speed. These "slow models usually drive a larger, heavier, 4-bladed propeller. Page 1-18Counterclockwise Rotating Prop Ring Gear Sun Gear Planetary Gear Diaphragm Prop Shaft Page 1-19TPE331 Line Maintenance - Training Manual AIRFLOW STATIONS Pressure and Temperature values can be further identi- fied as static (s) or total (t). For example: For ease of identifying locations within the engine where pressure and temperature changes occur, aircraft Tt4 is Temperature total at station 4 engine manufacturers utilize a station number identifica- Pt2 is Pressure total at station 2 tion system: Ps5 is Pressure static at station 5 Station 1 is the ambient air conditions surrounding the engine. Station 2 is the inlet to the first stage compressor. Station 3 is compressor discharge air. This is the area of highest pressure within the engine. - Station 4 is the inlet to the first stage turbine. This is the area of highest temperature within the engine. Station 5 is the turbine discharge or exhaust. These station numbers are then combined with a "P" for pressure or "T" for temperature. For example P3 identi- fies compressor discharge pressure. T4 identifies turbine inlet temperature. Intermediate locations between sta- tions are identified with a decimal point. For example, the inlet to the second stage stator where interstage tur- bine temperature (ITT) probes are located is identified as Station 4.1. Page 1-20Location for pressure And temperature changed Airflow Stations Pressure of engine 1 2 4 4.1 5 EGT (or T4 C Sample = P3 = Pressure T4 = Temperature (High Tem) Page 1-21TPE331 Line Maintenance - Training Manual MODEL NUMBERS To fully understand the the breakdown of the model number must be understood. Over the years AlliedSignal has produced many variations of the TPE331. In this example, the TPE331-10UGR-511H will be used: TPE means turboprop engine 331 is the series number assigned by AlliedSignal -10 identifies the FAA power class certification U,G, and R are all modifiers to -10 to indicate unique installations "U" means the air inlet is up "G" indicates the engine is equipped with the strain gage torque system "R" signifies the engine has automatic performance reserve (APR) "511" indicates the engine configuration in that specific components may be identified The suffix "H" identifies the aircraft manufacturer, British Aerospace Page 1-22Identification Typical Model Number TPE331-10UGR-511H TPE - Turboprop Engine 331 - Engine MFR Series Indicator Honey well -10 - Power Class (Certification) U - Inlet Up G - Strain Gage R - Automatic Performance Reserve -511 - Configuration ( Type of H - Application -Aircraft Mfg. Page 1-23TPE331 Line Maintenance -Training Manual TPE331 RATING HORSEPOWER Terms used to describe the performance ratings of the TPE331 engine are as follows: - "Shaft horsepower" (SHP) defines the power available to the propeller. This is the power above that required to turn the compressor. - "Thermodynamic shaft horsepower" is the maxi- mum horsepower capability of an engine. This is the horsepower produced when an engine is operated to its maximum permitted turbine inlet temperature (T4) on a standard sea level day. Page 1-24TPE331 Rating Values - Horsepower Shaft Horsepower = Power available to prop Thermodynamic SHP = HP capability of the engine's power section when operated at maximum permitted turbine inlet temperature at standard sea level conditions P-72-00-012 Page 1-25TPE331 Line Maintenance -Training Manual FLAT RATING "Flat rating" is used by aircraft manufacturers when they select an engine that has a capability greater than the requirements of the aircraft. They then limit the power output of the engine. There are three distinct benefits derived from flat rating: 1. The engine will have the ability to make takeoff power at lower turbine temperatures over a wide range of outside air temperatures and pressure altitudes 2. Performance at altitude will be greatly enhanced 3. Longer engine life Page 1-26Flat Rating Engines having a greater thermodynamic power capability than required for design aircraft performance are often selected. These "oversized" engines are then certified to the flat rated value in their specific installation. Benefits from using flat rated engines: Lower turbine temperatures at takeoff Improved altitude performance Longer engine life Page 1-27TPE331 Line Maintenance -Training Manual FUEL CONSUMPTION When comparing engine performance, one of the most important considerations is how efficiently the power is produced. The amount of fuel consumed to produce a given horsepower is known as "specific fuel consumption" or SFC. A typical aircraft fuel system measures the volume of fuel consumed. This is displayed in pounds per hour (lbs./hr). To calculate fuel flow, specific fuel consumption found on the customer data sheet, is multiplied by the horsepower at which the SFC was calculated. Page 1-28Fuel Consumption SFC = Specific Fuel Consumption Measured as lbs (fuel) per H.P. per Hour SFC (lb/HP/Hr) X HP = P.P.H (lbs per Hour) Page 1-29TPE331 Line Maintenance - Training Manual PERFORMANCE RATINGS OF TPE331 MODELS Compare the performance ratings for -1 through -12 engines. Notice the modifiers on the and -10 engines. These temperatures represent the effects of flat rating engines. Each engine will make takeoff power below their turbine temperature limits up to the ambi- ent temperatures indicated. Engines that are not flat rated, such as the -3 or would be unable to make takeoff power below their tur- bine temperature limits when operating in conditions above 59°F outside air temperatures. Page 1-30Performance Ratings - TPE331 Models Model -1 -2 -3 -5 -6 -8 -9 -10 -11 -12 Certification 665 715 840 776 715 715 865 900 1000 1050 (SHP) (1) (2) (3) (4) (5) Thermo 715 715 840 840 840 865 865 1000 1000 1100 Dynamic (SHP) SFC 0.605 0.558 0.590 0.590 0.590 0.568 0.568 0.558 0.558 0.547 (1) TO 75°F (2) TO 86°F (3) TO 92°F (4) TO 97°F (5) TO 91°F Page 1-31TPE331 Line Maintenance -Training Manual POWER CONVERSION-FREE Disadvantages of this type of conversion include a delayed "response rate" and less fuel efficiency The gas generator produced no useful work until it when compared to fixed shaft conversion type was coupled to the propeller to provide thrust. engines. One method is known as the "free turbine". An addi- tional turbine wheel is inserted into the exhaust gas path from the gas generator. This free or "power turbine" is then connected to the propeller through shafting and a gearbox assembly. Thermal energy that is in excess of the gas generator requirements is then directed to the power turbine where the required work is extracted and transmitted to the propeller. This type of power conversion offers several advan- tages: The aerodynamic or "fluidic" connection between the gas generator and power turbine is highly adapted to use in helicopters in that clutching problems are greatly reduced. This connection also provides very low propeller speeds, while maintaining relatively high gas generator speeds, which greatly reduces ler noise while taxiing. Page 1-32Power Conversion - Free FUEL (FREE) POWER TURBINE COMBUSTOR REDUCTION COMPRESSOR GAS GENERATOR GEARS TURBINE GAS GENERATOR Page 1-33TPE331 Line Maintenance - Training Manual POWER CONVERSION - FIXED Another method of power conversion is to add a third turbine wheel to the gas generator which is directly shafted to the propeller through the gearbox. This third turbine wheel extracts the required work needed above the requirements of the compressor section. This is the "fixed shaft" type. This type of power conversion also provides several dis- tinct advantages. One of these advantages is response rate. This means that because the gas generator is directly geared to the propeller, by increasing the heat energy to the turbine, an increase in output horsepower is caused, which is instantly sensed by the propeller and converted to useful thrust. In fact the response is only limited by the time required by the propeller to react. This is referred to as "instant response rate'. Another distinct advantage of fixed shaft type power conversion is lower specific fuel consumption. By elimi- nating the "fluidic coupling" a fixed shaft turboprop engine consumes less fuel per horsepower produced than a multiple spool engine. Page 1-34Power Conversion - Fixed Fuel Reduction Gears Combustor Compressor Turbine Page 1-35TPE331 Line Maintenance - Training Manual OPERATION CONSTANT SPEED ADVANTAGE The TPE331 is a fixed shaft type and is generally known as a "constant speed" engine. Though many different speeds may be selected for specific operations, the engine is designed to operate most efficienly at a con- stant speed (defined is 100% RPM). During flight opera- tion, 100% RPM is used for takeoff and landing with 96% as minimum cruise, and the engine is therefore being operated at or very near it's most efficient design point. This concept is important to understand and remember because it forms the basis for the power management theory and will make understanding of the propeller and fuel systems much All of these systems will be dis- cussed in detail in later sections. Page 1-36Constant Speed Advantage Compressors - Diffusers - Stators - Turbines Most Efficient At Or Near RPM Design Point Page 1-37TPE331 Line Maintenance - Training Manual CONSTANT SPEEDTHEORY To hold speed or RPM constant, turbine power must equal propeller load. Power produced is relative to the amount of fuel added to create the necessary heat energy. engine propeller governing A typical propeller governing system is used to regulate selected RPM by changing propeller load, By increasing fuel to the engine the propeller governing system will increase propeller load, or blade angle, and thrust will also increase. Even though propeller thrust is being changed, engine speed will remain constant. If fuel is decreased the propeller governing system will decrease propeller load to maintain 100% RPM. Page 1-38Constant Speed Load Power + To Hold Speed Constant, Excess Turbine Power Must Equal Propeller Load Page 1-39TPE331 Line Maintenance - Training Manual POWER LIMITS Maximum power output is limited by one of two factors, torque (horsepower) or turbine temperature. Maximum torque limits are a function of the airframe manufacturer to fulfill aircraft design performance and maintain structural integrity. Maximum temperature limits are a function of the engine and depend upon material types and critical speeds. Even on aircraft equipped with auto- matic torque and temperature limiting functions, the pilot must be aware of these limits. The power lever should be advanced to the torque or temperature limit - WHICHEVER COME Disregarding these limits may result in shorter engine increased maintenance and operating costs. Page 1-40Power Limits Maximum power taken from the TPE331 is limited by: Torque (HP) = Determined by aircraft design performance and structural integrity Turbine Temperature = Determined by engine design - Whichever Limit Is Reached First - Page 1-41TPE331 Line Maintenance - Training Manual AMBIENT CONDITIONS - HOW THEY AFFECT ENGINE PERFORMANCE The following examples will show that increased ambi- ent temperature or altitude causes a decrease in avail- able power, because ambient conditions (air density) directly affects which limit, torque or temperature, will be reached first. The examples assume a TPE 331-10 is operating at 100% RPM and the power lever has been advanced to the maximum turbine inlet temperature or thermodynamic limit. THERMODYNAMIC - STANDARD DAY SEA LEVEL On a standard sea level day the compressor is flowing approximately 7.6 pounds per second. This temperature is achieved by adding 558 pounds per hour of fuel, and 1000 shaft horsepower is being produced at 1100°C tur- bine inlet temperature (TIT). Notice that the thermody- namic shaft horsepower and temperature limits are reached simultaneously. Page 1-42Thermodynamic - STD Sea Level Airflow At 100% RPM = 7.6 Ib/sec T/G HP 1000 % = (°C) TIT 1100 Fuel 558 PPH Limit (PPH) C Page 1-43TPE331 Line Maintenance - Training Manual -29°C OUTSIDE AIR TEMPERATURE/SEA LEVEL (OAT/SL) - EXCEED HP LIMIT With cold or more dense air, advancing the power lever to the thermodynamic temperature limit gives us approximately 9.2 pounds per second air flow with 710 pounds per hour fuel flow. The higher fuel flow is due to the increase in air density. Under these conditions the engine is producing 1395 shaft horsepower. This is obviously an overtorque condition and illustrates the requirement for a torque limit as well as a tempera- ture limit. Page 1-44-29°C OAT/SL - Exceed HP Limit Airflow At 100% RPM = 9.2 Ib/sec Change Airflow Fuel TIT HP From Std . 21% Inc 27% Inc = Limit Result 40% Inc T/G HP 1395 TIT 1100 Fuel 710 Limit (PPH) C Page 1-45