Questions and Answers
What happens to the flow of a positive displacement swash plate pump when the swash plate is perpendicular to the axis of the pump?
What moves the swash plate away from the minimum stroke position in a fuel pump?
At what condition is the burner fuel flow at maximum?
How is servo pressure, used to control fuel pump 'Swash Plate' angle, obtained?
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What would be the effect on the engine if the B.P.C half ball valve in the servo line sticks open?
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What is the purpose of an A.C.U fitted to a gas turbine engine?
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What happens to the pump output if fuel pump servo pressure is reduced?
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What is the function of the swash plate in a fuel pump?
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What is the purpose of the Barometric Pressure Controller in a gas turbine engine fuel system?
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What must be done after the fuel control unit has been replaced on an aircraft gas turbine engine?
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What is the function of a kinetic valve in a gas turbine engine fuel system?
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What is the effect of increasing air intake pressure on fuel flow to the burners?
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What is the purpose of the attenuator in a gas turbine engine fuel system?
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Why is a hydromechanical governor fitted to a gas turbine engine fuel pump?
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What is the normal fuel-to-air ratio for successful combustion in a gas turbine engine?
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What influences the operation of an automatic fuel control unit on a turbojet engine?
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What happens to specific fuel consumption at altitude?
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During stabilized running conditions, the spill or half-ball valve is typically?
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What is the purpose of the L.P. pump?
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How are the fuel pump plungers lubricated?
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Which forces control the maximum RPM governor in a non-hydromechanical swashplate type of pump?
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Why do the holes in the body of the duple burner provide air to the shroud around the burner head?
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What does a fuel heater prevent?
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What is the main purpose of the Barometric Pressure Control?
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What is the function of the E.E.C. on a FADEC engine?
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During normal running conditions, is combustion?
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What occurs when the swash plate of a positive displacement swash plate pump is perpendicular to the axis of the pump?
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What is the primary cause of surge in a jet engine?
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What happens when the channel reset is activated on a FADEC engine?
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How is servo pressure obtained in a jet engine fuel system?
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What happens to the maximum RPM of a turbine engine when the fuel specific gravity decreases and the engine is fitted with an uncompensated fuel governor?
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What is the primary function of the fuel control unit in a jet engine?
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What limits the maximum RPM of a turbine engine?
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Why is it necessary to control fuel supply during rapid acceleration?
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What type of fuel control unit is most commonly used in modern jet engines?
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What is the purpose of the kinetic valve in a fuel pump?
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What is the position of the swash plate in a fuel pump when static?
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During stabilized running conditions, the spill or half ball valve is?
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What is the primary function of the high-pressure fuel pump in a gas turbine engine aircraft?
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What is the position of the pressurization valve and the dump valve in a jet engine fuel system when the engine is shut down?
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Which of the following air mixtures weighs the most?
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What does a mixture ratio of 11:1 normally refer to?
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What is the primary purpose of trimming a turbine engine fuel control unit?
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What type of fuel control is used on most of today's turbine engines?
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When is the trimming of a turbine engine most accurate?
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What signal does an H.M.U receive?
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When trimming a turbine engine, the fuel control is adjusted to:
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What is the function of a supervisory electronic engine control (E.E.C)?
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What causes the fuel divider valve to open in a turbine engine duplex fuel nozzle?
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What is the safety backup available for the engine fuel flow if the valve on a vane type fuel flow measuring device becomes stuck?
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What is the primary advantage of the duplex fuel nozzle used in many turbine engines?
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What is the purpose of the flow divider in a turbine engine duplex fuel nozzle?
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Which of the following turbine fuel filters has the greatest filtering action?
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Where is the engine fuel shutoff valve usually located?
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If a FADEC loses its ADC input, what will it do in the short term?
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The primary purpose of an E.E.C is to:
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When both FADEC channels are healthy, what happens?
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What is the purpose of the LP fuel pump?
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What is the primary function of a FADEC system?
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What type of filter is typically used on the inlet side of a fuel pump?
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What happens to the pressure drop across the Fuel Control Unit throttle orifice when the throttle is selected to increase power?
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What action does the E.E.C take when it senses a fault on the engine?
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What does the E.E.C control in-flight?
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What does a FADEC system not have?
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What prevents fuel from spilling out of fuel tank vents during aerobatic maneuvers?
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What is the purpose of the low-pressure fuel pump in a FADEC system?
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Where would you disconnect the system to carry out flow checks after a bag tank replacement?
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What happens when Channel A fails to receive information from a sensor in a FADEC system?
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What is the purpose of a silver strip on a fuel filter?
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How is fuel flow controlled in a FADEC engine with a hydromechanical fuel system?
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What should the RPM be set to on approach for maximum acceleration?
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What is the primary purpose of cross-feeding fuel from one tank to another?
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What type of pressure controls the swash plate in the fuel pump of an axial flow gas turbine engine?
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What happens if the air data inputs to the FADEC E.C.U fail?
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Why are the end fittings on a fuel non-return valve normally of different sizes?
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What components make up a FADEC system?
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What does a fuel heater prevent in a FADEC system?
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What type of sensors does the E.E.C receive signals from?
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When re-light is required in flight on a FADEC engine, what happens to the igniter selection?
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When does the E.E.C channel change over occur?
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Where is the fuel heater located in the fuel system?
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What is the combined output of all the scavenge pumps in a lubrication system compared to the pressure pump output?
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What is the primary power source for the E.E.C?
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What happens when the knife-edge blade in a kinetic valve is fully in?
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What is the purpose of the kinetic valve in a gas turbine engine fuel system?
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What is the purpose of the acceleration control unit?
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In a FADEC system, what does the E.E.C measure along with RPM?
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What is the purpose of trimming in a gas turbine engine?
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How are the power supply windings for channel A and Channel B wound in a FADEC system?
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What happens if an Engine FADEC system loses air-data permanently?
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What is the main purpose of the fuel boost pumps in a gas turbine engine?
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What is the function of baffles in a rigid fuel tank?
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What is the forward idle setting of the thrust lever resolver angle?
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How are fuel pumps cooled?
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What happens to the fuel flow governor when the engine is at altitude?
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Study Notes
Swash Plate Pump
- If the swash plate is perpendicular to the axis of the pump, the flow will be zero
- The swash plate angle is controlled by servo pressure, which is obtained from pump delivery pressure through variable restrictions
- A spring moves the swash plate away from the minimum stroke position
Fuel System
- The burner fuel flow is at maximum at sea level (ISA)
- Fuel flow responds to mass airflow rate through the engine during aircraft acceleration
- Fuel flow is increased at a controlled rate during acceleration to prevent surge and the risk of flame-out
- The barometric pressure controller (BPC) controls fuel pump output in relation to the pressure variation at the intake
Fuel Pump
- The high-pressure fuel pump is fitted in a gas turbine engine aircraft to provide the majority of the fuel pressure to the engine
- The low-pressure pump prevents cavitation of the high-pressure fuel pump
- The fuel pump plungers are lubricated by the fuel itself
Governor
- The hydromechanical governor is fitted to a gas turbine engine fuel pump to enable the engine to operate over a wide range of fuel specific gravities
- The governor controls the maximum RPM of the engine by reducing the fuel pump stroke when maximum RPM is reached
Fuel Control Unit (FCU)
- The FCU is trimmed to obtain maximum thrust output when desired
- The FCU is adjusted to set idle RPM and maximum speed or EPR
- Trimming is most accurate in no wind and low moisture conditions
Electronic Engine Control (EEC)
- The EEC receives engine operating information and adjusts a standard hydromechanical fuel control unit to obtain the most effective engine operation
- The EEC is a system that controls engine operation according to ambient temperature, pressure, and humidity
FADEC System
- FADEC (Full Authority Digital Engine Control) system has electronic control of the hydro-mechanical fuel control unit in all modes
- Active control switchover occurs on engine start-up only
- Channel reset selects standby, which becomes active on the next start
Fuel Nozzle
- The duplex fuel nozzle provides better atomization and uniform flow pattern
- The flow divider in a turbine engine duplex fuel nozzle creates the primary and secondary fuel supplies
- The valve on a vane type fuel flow measuring device becomes stuck, and a differential pressure bypass valve is the safety backup available for the engine fuel flow### Engine Fuel Shutoff Valve
- Located downstream of the engine driven fuel pump
FADEC System
- Consists of H.M.U, sensors, and an E.E.C
- Primary purpose is to save fuel, reduce crew workload, and reduce maintenance costs
- Receives primary power from a separate permanent magnet alternator
- E.E.C measures pressure and temperature along with RPM
- Can change digital inputs into analogue format to provide glass cockpit information and reduce flight crew workload
- Has an automatic starting capability
- Does not have automatic control of engine fire bottles
Throttle and Fuel Control
- Throttle position is controlled by the crew or autothrottle
- Fuel flow is controlled by the E.E.C in flight
- Trimming is adjusting idle speed and maximum thrust
- Fuel trimmer unit is adjusted automatically at altitude
FADEC Channels
- Both channels are operating, but either one can be in command if they are both healthy
- If a channel fails to receive information from a sensor, it will take the information from the other channel
- If all air data input fails, the E.C.U reverts to an alternate (Fail-safe) mode
Engine Performance
- Optimized performance is the reason FADEC was introduced
- FADEC ensures efficiency is always maximum
Fuel System
- Engine fuel pump has a wire mesh filter
- Pressure drop across the Fuel Control Unit throttle orifice drops then increases due to increasing pump output
- Fuel boost pumps are cooled using fuel
- Main purpose of the fuel boost pumps is to provide fuel pressure to both engine pumps
Sensors and Valves
- Silver strip on a fuel filter detects sulphur in fuel
- Baffles in a rigid fuel tank prevent surge
- End fittings on a fuel non-return valve are different sizes to prevent incorrect installation
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Description
Test your knowledge of positive displacement pumps and burners, including swash plate pumps and fuel flow. This quiz covers key concepts and principles related to these mechanical systems.