AMTE 135 Quiz 2
FUEL PUMPS
Q: What do all aircraft other than those with gravity-feed systems have?
A: All aircraft have at least one fuel pump to deliver clean fuel under pressure to the fuel metering device for each engine.
Q: What are engine-driven pumps?
A: The primary delivery device for fuel in most aircraft.
Q: What are auxiliary pumps also known as?
A: Booster pumps or boost pumps.
Q: When are auxiliary pumps used?
A: To provide fuel under positive pressure to the engine-driven pump and during starting when the engine-driven pump is not yet up to speed for sufficient fuel delivery.
Q: Why are auxiliary pumps used during takeoff and at high altitude?
A: To guard against vapor lock.
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HAND-OPERATED FUEL PUMPS
Q: What are hand-operated fuel pumps used for?
A: To back up the engine-driven pump and to transfer fuel from tank to tank.
Q: What are hand-operated pumps also known as?
A: Wobble pumps.
Q: What type of pump is a wobble pump?
A: A double-acting pump that delivers fuel with each stroke of the pump handle.
Q: How do simple hand primers on modern light aircraft work?
A: They are single-acting piston pumps that pull fuel in when the knob is pulled aft and push fuel to the cylinders when pushed forward.
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CENTRIFUGAL BOOST PUMPS
Q: What is the most common type of auxiliary fuel pump on large and high-performance aircraft?
A: The centrifugal pump.
Q: How does a centrifugal boost pump work?
A: It takes in fuel at the center of an impeller and expels it to the outside as the impeller turns.
Q: What prevents fuel from flowing back through a centrifugal pump?
A: An outlet check valve.
Q: What are centrifugal pumps used for?
A: To supply and back up the engine-driven pump and to transfer fuel from tank to tank.
Q: What does a centrifugal pump prevent?
A: Vapor lock, by ensuring positive pressure throughout the fuel system.
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EJECTOR PUMPS
Q: What do ejector pumps ensure?
A: That liquid fuel is always at the inlet of the pump.
Q: How do ejector pumps work?
A: Fuel is circulated back into the tank section through a venturi, creating low pressure that draws in fuel from outside the tank pump area.
Q: What helps ejector pumps maintain a positive head of fuel?
A: Baffle check valves.
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PULSATING ELECTRIC PUMPS
Q: Where are pulsating electric pumps commonly used?
A: In general aviation aircraft.
Q: How does a pulsating electric pump operate?
A: A solenoid moves a plunger back and forth, drawing in and pushing out fuel in a pulsating motion.
Q: When is a pulsating electric pump used?
A: During starting, takeoff, and at high altitudes to prevent vapor lock.
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VANE TYPE FUEL PUMPS
Q: What is the most common type of fuel pump found on reciprocating-engine aircraft?
A: Vane-type fuel pump.
Q: What kind of displacement pump is a vane-type?
A: Constant displacement pump that moves a constant volume of fuel with each revolution.
Q: How is a vane pump driven?
A: Electrically when used as an auxiliary pump, or by the accessory gear box when engine-driven.
Q: What is the basic mechanism of a vane pump?
A: An eccentric rotor with sliding vanes that create and reduce volume to move fuel.
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FUEL FILTERS
Q: What are the two main types of fuel cleaning devices?
A: Fuel strainers and fuel filters.
Q: What do strainers trap?
A: Large pieces of debris.
Q: What do filters trap?
A: Fine sediment and water.
Q: Where is the first fuel cleaning device located?
A: At the outlet of the fuel tank.
Q: What is the purpose of the sump in a fuel tank?
A: To collect debris in the lowest part of the tank for draining before flight.
Q: Where is the main strainer usually located?
A: Between the fuel tank and the engine-driven fuel pump at the low point in the system.
Q: What is the purpose of a finger screen?
A: To trap debris while allowing fuel to flow from the tank outlet.
Q: Where is the main fuel strainer mounted on most aircraft?
A: At a low point on the engine firewall with an accessible drain.
Q: What is trapped in the bottom of a strainer bowl?
A: Water and large debris.
Q: What type of filter construction do larger aircraft use?
A: Double-screen construction with a fine mesh and a cone-shaped inner screen.