Subject N - Engine Fuel Systems Flashcards
What is the purpose of strainers in a fuel system?
They are used to prevent foreign matter from entering the carburetor.
Why do carburetors in aircraft have a mixture control?
Because air density changes with altitude, which affects the air-fuel mixture. The mixture control provides a means to adjust for the correct mixture at different altitudes.
What two items are adjusted when setting idling conditions on a float carburetor?
The throttle stop for idling RPM, and the idle mixture through the idle needle valve.
What is the purpose of fuel selector valves?
They provide a means of shutting off fuel flow, cross-feed for tank and engine selection and for fuel transfer.
What should be looked for when inspecting an engine driven fuel pump?
Look for fuel leaks and security of mounting.
What is the purpose of the engine driven fuel pump?
The engine driven fuel pump delivers a continuous supply of fuel at the proper pressure at all times during engine operation.
What type of fuel pump is generally used with large reciprocating engines?
A positive-displacement rotary-vane type pump.
What happens to excess fuel not required by the engine in a constant displacement pump?
The pressure relief valve opens and the fuel is routed back to the inlet side of the pump.
What is the most common type of fuel boost pump?
The electrically driven centrifugal type pump.
What are the functions of the boost pump?
First, during starting the boost pump supplies fuel to the engine pump for starting
They are also used to maintain pressure in the fuel lines to prevent the fuel from boiling off at altitude.
Finally boost pumps act as backup in the event the engine driven pump fails.
What is the purpose of they bypass valve in the engine driven fuel pump?
The bypass valve provides a path around the pump vanes for starting the engine, and to allow fuel to bypass the pump in case of pump failure
What is the purpose of using boost pumps in a fuel system?
A main function of the boost pump is to keep the pressure on the suction side of the engine driven pump from becoming low enough to permit the fuel to boil when operating at high altitudes.
Electric boost pumps are used to supply fuel to a pressure carburetor during engine starting and in case of engine driven pump failure.
What are three general causes of vapor lock?
Low fuel pressure, high fuel temperatures, and excessive fuel turbulence.
Turbine engine fuel pumps may be divided into what two distinct system categories
Constant displacement and variable displacement.
What category is a turbine engine driven gear-type pump?
Constant displacement.
