Aircraft Fuel Systems Flashcards
What are two reasons Prist is added to the fuel that is used in a turbojet aircraft?
Prist is a biocidal agent that (1) kills the scum-forming bacteria in the fuel tank, and (2) acts as an antifreeze agent, lowering the freezing point of the entrained water that is released from the fuel.
What are two types of fuel cells that are used in modern aircraft?
Integral fuel cells (cells that are a sealed-off portion of the structure) and bladder-type cells.
Why are fuel tanks divided into compartments or have baffles installed in them?
Keep the fuel from surging back and forth as the aircraft changes its attitude in flight.
What is meant by an integral fuel cell?
A part of the structure in which all of the seams and joints are sealed so they will be fuel tight. The structure itself then becomes the fuel tank.
Where are fuel system strainers located?
One strainer is located in the outlet to the tank, and the main strainer is located in the fuel line between the outlet of the fuel tank and the inlet to the fuel metering device.
What are three uses of a centrifugal booster pump that is installed in an aircraft fuel tank?
Booster pumps are used to produce fuel pressure for starting the engine, to keep the fuel from vapor locking at high altitude, and to transfer fuel from one tank to another.
What is meant by a compensated engine-driven fuel pump?
It varies its outlet fuel pressure so it will stay a constant amount higher than the pressure of the air that is entering the carburetor.
Why do engine-driven fuel pumps have a bypass valve in them?
It allows fuel from the booster pump to flow around the engine-driven pump mechanism for starting the engine and to supply the engine with fuel if the engine-driven pump should fail.
Why must an aircraft fuel valve have a detent in its operating mechanism?
It gives the pilot a positive indication by feel when the selector valve is in the full ON and full OFF position.
What characteristic of the fuel is measured with the mass-flow fuel flowmeter that is used with turbine engine aircraft?
The density of the fuel.
What is used as a flowmeter for a fuel-injected, horizontally opposed aircraft engine?
A pressure gage that measures the pressure drop across the injector nozzles in the engine.
What is meant by a cross-feed system in an aircraft fuel system?
A cross-feed system allows fuel from any tank to flow to any engine.
Why do some aircraft have provisions for jettisoning fuel in flight?
Aircraft that are certificated with a higher takeoff weight than their allowable landing weight must have provision for jettisoning fuel. This allows enough fuel to be dumped to bring the weight down to that allowed for landing in case an emergency occurs before this amount of fuel can be burned off.
What must be done to a welded fuel tank before it can be repaired by welding?
All of the fuel vapors must be purged by flowing live steam through the tank, by soaking it in boiling water, or by chemically neutralizing the fumes.
What safety precautions must be taken before a person enters the fuel cell of a large aircraft?
The cell must be thoroughly purged of all fumes, the person entering the cell must wear proper safety equipment, and there must be a person standing by on the outside of the cell.
