Powerplant fuel metering oral q

What is used to keep water, sediment, and foreign matter out of the carburetor?

The main fuel strainer.

Under what conditions is a reciprocating engine pre-oiled?

Prior to starting a new engine or one that has been serviced for storage. This ensures adequate lubrication on initial startup.

What are some of the sources used to heat the fuel in a turbine engine fuel system?

Bleed air and engine lubricating oil.

What purpose do turbine engine fuel control units serve?

They automatically meter fuel to the engine.

What are the two basic types of turbine engine fuel control units?

Hydro-mechanical and electronic.

What are the engine variables detected by the fuel control unit?

Power lever position, engine RPM, compressor inlet temperature, compressor inlet pressure, compressor discharge pressure, and burner pressure.

What are the two major components of a Supervisory Electronic Engine Control (EEC)?

The Electronic Control Unit (computer) and the hydro-mechanical fuel control.

What are the different engine indications used for trimming a turbine engine?

Either EPR (Engine Pressure Ratio) or RPM is used, depending on the particular engine.

What maintenance adjustments are normally allowed on an installed hydro-mechanical fuel control?

Specific gravity for fuel, idle RPM, and maximum RPM.

What is the purpose of a duplex fuel nozzle?

A duplex fuel nozzle discharges two different spray patterns (wider during startup/acceleration, narrower at higher speeds).

What are the functions of the pressurizing and dump valve?

The pressurizing portion provides primary and secondary fuel flow to dual-line duplex fuel nozzles, and the dump portion allows fuel to drain from the manifold after engine shutdown.

What type of pump can vary the amount of fuel discharge regardless of speed?

A variable displacement pump.

What is the purpose of a pressure relief valve in a constant displacement pump?

It returns excess fuel that is not required by the engine to the inlet side of the pump.

What type of engine-driven fuel pump is widely used other than gear or piston pumps?

A rotary vane type.

What function do fuel boost pumps perform?

They supply pressurized fuel to the engine-driven fuel pump, which helps prevent vapor lock and cavitation.

What is a commonly used type of fuel boost pump?

The centrifugal type.

What causes vapor lock and why is it a concern?

Vapor lock is caused by insufficient fuel pressure, high fuel temperatures, and excessive fuel turbulence, which may completely block fuel flow resulting in engine failure.

What function does the engine-driven pump on a turbine engine perform?

It provides a continuous supply of fuel at the proper pressure while the engine is running.

Name the two types of turbine engine pumps.

Constant and variable displacement.

What category is a gear-type pump classified in?

Constant displacement.

What is the purpose of a sheer section of the driveshaft in a dual element constant displacement pump?

If one element seizes, a portion of the drive shaft shears, allowing the other element to continue to operate.

What purpose do fuel selector valves serve?

They allow tank and engine selection and provide a means for shutting off fuel flow.