AMTE 135 Quiz 2

What do all aircraft other than those with gravity-feed systems have?

At least one fuel pump to deliver clean fuel under pressure to the fuel metering device for each engine.

What are engine-driven pumps?

The primary delivery device for fuel in most aircraft.

What are auxiliary pumps also known as?

Booster pumps or boost pumps.

When are auxiliary pumps used?

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.

Why are auxiliary pumps used during takeoff and at high altitude?

To guard against vapor lock.

What are hand-operated fuel pumps used for?

To back up the engine-driven pump and to transfer fuel from tank to tank.

What are hand-operated pumps also known as?

Wobble pumps.

What type of pump is a wobble pump?

A double-acting pump that delivers fuel with each stroke of the pump handle.

How do simple hand primers on modern light aircraft work?

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.

What is the most common type of auxiliary fuel pump on large and high-performance aircraft?

The centrifugal pump.

How does a centrifugal boost pump work?

It takes in fuel at the center of an impeller and expels it to the outside as the impeller turns.

What prevents fuel from flowing back through a centrifugal pump?

An outlet check valve.

What are centrifugal pumps used for?

To supply and back up the engine-driven pump and to transfer fuel from tank to tank.

What does a centrifugal pump prevent?

Vapor lock, by ensuring positive pressure throughout the fuel system.

What do ejector pumps ensure?

That liquid fuel is always at the inlet of the pump.

How do ejector pumps work?

Fuel is circulated back into the tank section through a venturi, creating low pressure that draws in fuel from outside the tank pump area.

What helps ejector pumps maintain a positive head of fuel?

Baffle check valves.

Where are pulsating electric pumps commonly used?

In general aviation aircraft.

How does a pulsating electric pump operate?

A solenoid moves a plunger back and forth, drawing in and pushing out fuel in a pulsating motion.

When is a pulsating electric pump used?

During starting, takeoff, and at high altitudes to prevent vapor lock.

What is the most common type of fuel pump found on reciprocating-engine aircraft?

Vane-type fuel pump.

What kind of displacement pump is a vane-type?

Constant displacement pump that moves a constant volume of fuel with each revolution.

How is a vane pump driven?

Electrically when used as an auxiliary pump, or by the accessory gear box when engine-driven.

What is the basic mechanism of a vane pump?

An eccentric rotor with sliding vanes that create and reduce volume to move fuel.

What are the two main types of fuel cleaning devices?

Fuel strainers and fuel filters.

What do strainers trap?

Large pieces of debris.

What do filters trap?

Fine sediment and water.

Where is the first fuel cleaning device located?

At the outlet of the fuel tank.

What is the purpose of the sump in a fuel tank?

To collect debris in the lowest part of the tank for draining before flight.

Where is the main strainer usually located?

Between the fuel tank and the engine-driven fuel pump at the low point in the system.

What is the purpose of a finger screen?

To trap debris while allowing fuel to flow from the tank outlet.

Where is the main fuel strainer mounted on most aircraft?

At a low point on the engine firewall with an accessible drain.

What is trapped in the bottom of a strainer bowl?

Water and large debris.

What type of filter construction do larger aircraft use?

Double-screen construction with a fine mesh and a cone-shaped inner screen.