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What factor is not used in the operation of an aircraft gas turbine engine fuel control unit?
Mixture control position
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In order to stabilize cams, springs, and linkages within the fuel control, manufacturers generally recommend that all final turbine engine trim adjustments be made in the
increase direction.
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When trimming a turbine engine, the fuel control is adjusted to
set idle RPM and maximum speed or EPR.
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A supervisory electronic engine control (EEC) is a system that receives engine operating information and
adjusts a standard hydromechanical fuel control unit to obtain the most effective engine operation.
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A full-authority electronic engine control (EEC) is a system that receives all the necessary data for engine operation and
develops the commands to various actuators to control engine parameters.
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In a supervisory EEC system, any fault in the EEC that adversely affects engine operation
causes an immediate reversion to control by the hydromechanical fuel control unit.
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The active clearance control (ACC) portion of an EEC system aids turbine engine efficiency by
ensuring turbine blade to engine case clearances are kept to a minimum by controlling case temperatures.
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What should be checked/changed to ensure the validity of a turbine engine performance check if an alternate fuel is to be used?
Fuel specific gravity setting.
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The generally acceptable way to obtain accurate on-site temperature prior to performing engine trimming is to
hang a thermometer in the shade of the nose wheel-well until the temperature reading stabilizes.
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An aircraft should be facing into the wind when trimming an engine. However, if the velocity of the wind blowing into the intake is excessive, it is likely to cause a
false high compression and turbine discharge pressure, and a subsequent low trim.
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Generally, the practice when trimming an engine is to
turn all accessory bleed air off.
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What method is ordinarily used to make idle speed adjustments on a float-type carburetor?
An adjustable throttle stop or linkage.
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For what primary purpose is a turbine engine fuel control unit trimmed?
To obtain maximum thrust output when desired.
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Which type of fuel control is used on most of today's turbine engines?
Hydromechanical or electronic.
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In turbine engines that utilize a pressurization and dump valve, the dump portion of the valve
drains the engine manifold lines to prevent fuel boiling and subsequent deposits in the lines as a result of residual engine heat (at engine shutdown).
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What effect does high atmospheric humidity have on the operation of a jet engine?
Has little or no effect.
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What are the positions of the pressurization valve and the dump valve in a jet engine fuel system when the engine is shut down?
Pressurization valve closed, dump valve open.
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Which of the following is NOT an input parameter for a turbine engine fuel control unit?
Ambient humidity.
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Which of the following statements concerning a centrifugal-type fuel boost pump located in a fuel supply tank is NOT true?
The centrifugal-type pump is classified as a positive displacement pump.
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Where is the engine fuel shutoff valve usually located?
Aft of the firewall.
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Boost pumps in a fuel system
provide a positive flow of fuel to the engine pump.
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What is the purpose of the fuel transfer ejectors?
To assist in the transfer of fuel from the main tank to the boost pump sump.
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The fuel pump relief valve directs excess fuel to the
inlet side of the fuel pump.
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The primary condition(s) that allow(s) microorganisms to grow in the fuel in aircraft fuel tanks is (are)
the presence of water.
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It is desirable that fuel lines have a gentle slope upward or downward and not have sharp curves or sharp rises and/or falls in order to
prevent vapor lock.
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Where should the main fuel strainer be located in the aircraft fuel system?
At the lowest point in the fuel system.
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Where physical separation of the fuel lines from electrical wiring or conduit is impracticable, locate the fuel line
below the wiring and clamp the line securely to the airframe structure.
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What is a characteristic of a centrifugal-type fuel boost pump?
It separates air and vapor from the fuel.
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A pilot reports that the fuel pressure fluctuates and exceeds the upper limits whenever the throttle is advanced. The most likely cause of the trouble is
a sticking fuel pump relief valve.
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Fuel pump relief valves designed to compensate for atmospheric pressure variations are known as
balanced-type relief valves.
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Fuel lines are kept away from sources of heat, and sharp bends and steep rises are avoided to reduce the possibility of
vapor lock.
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Fuel crossfeed systems are used in aircraft to
maintain aircraft stability.
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Kerosene is used as turbine engine fuel because
kerosene has more heat energy per gallon and lubricates fuel system components.
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What are the principal advantages of the duplex fuel nozzle used in many turbine engines?
Provides better atomization and uniform flow pattern.
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It is necessary to control acceleration and deceleration rates in turbine engines in order to
prevent blowout or die-out.
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Which of the following turbine fuel filters has the greatest filtering action?
Micron.
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What is the purpose of the flow divider in a turbine engine duplex fuel nozzle?
Creates the primary and secondary fuel supplies.
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What causes the fuel divider valve to open in a turbine engine duplex fuel nozzle?
Fuel pressure.
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Frequently, an aircraft's auxiliary power unit (APU) generator
is identical to the engine-driven generators.
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Fuel is normally supplied to an APU from
the airplane's main fuel supply.
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An APU is usually rotated during start by
an electric starter.
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The function of an APU air inlet plenum is to
stabilize the pressure of the air before it enters the compressor.
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When in operation, the speed of an APU
remains at or near rated speed regardless of the load condition.
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Generally, when maximum APU shaft output power is being used in conjunction with pneumatic power
pneumatic loading will be automatically modulated to maintain a safe EGT.
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When necessary, APU engine cooling before shutdown may be accomplished by
closing the bleed air valve.
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Usually, most of the load placed on an APU occurs when
the bleed air valve is opened.
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Fuel scheduling during APU start and under varying pneumatic bleed and electrical loads is maintained
automatically by the APU fuel control system.
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On APU's equipped with a free turbine and load compressor, the primary function of the load compressor is to
provide bleed air for aircraft pneumatic systems.
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