PP Engine Fuel Systems

During what period does the fuel pump bypass valve open and remain open?

When the fuel pump pressure is greater than the demand of the engine.
When the boost pump pressure is greater than fuel pump pressure.
When the fuel pump output is greater than the demand of the carburetor.

Which of the following statements concerning a centrifugal-type fuel boost pump located in a fuel supply tank is NOT true?

Air and fuel vapors do not pass through a centrifugal-type pump.
Fuel can be drawn through the impeller section of the pump when it is not in operation.
The centrifugal-type pump is classified as a positive displacement pump.

Where is the engine fuel shutoff valve usually located?

Aft of the firewall.
Adjacent to the fuel pump.
Downstream of the engine-drive fuel pump.

Boost pumps in a fuel system

operate during takeoff only.
are primarily used for fuel transfer.
provide a positive flow of fuel to the engine pump.

Refer to Figure 7. What is the purpose of the fuel transfer ejectors?

To supply fuel under pressure to the engine-driven pump.
To assist in the transfer of fuel from the main tank to the boost pump sump.
To transfer fuel from the boost pump sump to the wing tank.

What is the purpose of an engine-driven fuel pump bypass valve?

To divert the excess fuel back to the main tank.
To prevent a damaged or inoperative pump from blocking the fuel flow of another pump in series with it.
To divert the excess fuel from the pressure side of the pump to the inlet side of the pump.

Most large aircraft reciprocating engines are equipped with which of the following types of engine-driven fuel pumps?

Rotary vane-type fuel pump.
Centrifugal-type fuel pump.
Gear-type fuel pump.

When an electric primer is used, fuel pressure is built up by the

internal pump in the primer solenoid.
suction at the main discharge nozzle.
booster pump.

The fuel pump relief valve directs excess fuel to the

fuel tank return line.
inlet side of the fuel pump.
inlet side of the fuel strainer.

Which type of pump is commonly used as a fuel pump on reciprocating engines?

Gear.
Impeller.
Vane.

The purpose of the diaphragm in most vane-type fuel pumps is to

maintain fuel pressure below atmospheric pressure.
equalize fuel pressure at all speeds.
compensate fuel pressures to altitude changes.

The primary condition(s) that allow(s) microorganisms to grow in the fuel in aircraft fuel tanks is (are)

warm temperatures.
the presence of water.
the presence of dirt or other particulate contaminants.

It is desirable that fuel lines have a gentle slope upward or downward and not have sharp curves or sharp rises and/or falls in order to

prevent vapor lock.
prevent stagnation or “pooling” of fuel in the fuel lines.
minimize the generation of static electricity by decreasing fluid friction in the lines.

The fuel systems of aircraft certificates in the standard classification must include which of the folloiwng?

An engine-driven fuel pump and at least one auxiliary pump per engine.
A positive means of shutting off the fuel to all engines.
A reserve supply of fuel, available to the engine only after selection by the flight crew, sufficient to operate the engines at least 30 minutes at METO power.

Where is the main fuel strainer located in the aircraft fuel system?

At the highest point in the fuel system.
At the lowest point in the fuel system.
At the inlet chamber of the carburetor.

Where physical separation of the fuel lines from electrical wiring or conduit is impracticable, locate the fuel line

below the wiring and clamp the line securely to the airframe structure.
above the wiring and clamp the line securely to the airframe structure.
inboard of the wiring and clamp both securely to the airframe structure.

What is a characteristic of a centrifugal-type fuel boost pump?

It separates air and vapor from the fuel.
It has positive displacement.
It requires a relief valve.

The Federal Aviation Regulations require the fuel low rate for gravity systems (main and reserve) to be

125 percent of the takeoff fuel consumption of the engine.
125 percent of the maximum, except takeoff, fuel consumption of the engine.
150 percent of the takeoff fuel consumption of the engine.

Fuel boost pumps are operated

to provide a positive flow of fuel to the engine.
a sticking fuel pump relief valve.
an air leak at the fuel pump relief-valve body.

A pilot reports that the fuel pressure fluctuates and exceeds the upper limits whenever the throttle is advanced. The most likely cause of the trouble is

a ruptured fuel pump relief valve diaphragm.
a sticking fuel pump relief valve.
an air leak at the fuel pump relief-valve body.

A fuel strainer or filter must be located between the

boost pump and tank outlet.
tank outlet and the fuel metering device.
boost pump and engine-driven fuel pump.

Fuel pump relief valves designed to compensate for atmospheric pressure variations are known as

compensated-flow valves.
pressurized-relief valves.
balanced-type relief valves.

Fuel lines are kept away from sources of heat, and sharp bends and steep rises are avoided to reduce the possibility of

liquid lock.
vapor lock.
positive lock.

Fuel cross-feed systems are used in aircraft to

purge the fuel tanks.
jettison fuel in an emergency.
maintain aircraft stability.

If an engine equipped with a float-type carburetor backfires or misses when the throttle is advanced, a likely cause is that the

float level is too high.
main air bleed is clogged.
accelerating pump is not operating properly.

A fuel pressure relief valve is required on

engine-driven diaphragm-type fuel pumps.
engine-driven vane-type fuel pumps.
centrifugal fuel boost pumps.

A rotary-vane pump is best described as a

positive-displacement pump.
variable-displacement pump.
boost pump.

Fuel pressure produced by the engine-driven fuel pump is adjusted by the

bypass valve adjusting screw.
relief valve adjusting screw.
engine-driven fuel pump adjusting screw.

Kerosene is used as turbine engine fuel because

kerosene has very high volatility which aids in ignition and lubrication.
kerosene has more heat energy per gallon and lubricates fuel system components.
kerosene does not contain any water.

What are the principal advantages of the duplex fuel nozzle used in many turbine engines?

Restricts the amount of fuel flow to a level where more efficient and complete burning of the fuel is achieved.
Provides better atomization and uniform flow pattern.
Allows a wider range of fuels and filters to be used.

It is necessary to control acceleration and deceleration rates in turbine engines in order to

prevent blowout or die-out.
prevent overtemperature.
prevent friction between turbine wheels and the case due to expansion and contraction.

Which of the following turbine fuel filters has the greatest filtering action of any present-day filter type?

Micron filter.
Plain screen mesh filter.
Water screen filter.

What is the purpose of the flow divider in a turbine engine duplex fuel nozzle?

Allows an alternate flow of fuel if the primary flow clogs or is restricted.
Creates the primary and secondary fuel supplies.
Provides a flow path for bleed air which aids in the atomization of fuel.

What causes the fuel divider valve to open in a turbine engine duplex fuel nozzle?

Fuel pressure.
Bleed air after the engine reaches idle RPM.
An electronically operated solenoid.

How often should float carburetors be overhauled?

At engine overhaul.
Annually.
At engine change.

What is the final authority for the details of carburetor overhaul?

The local FAA safety inspector.
The Type Certificate Data Sheets for the engine.
The manufacturer’s recommendations.

Which statement is true regarding proper throttle rigging of an airplane?

The throttle stop on the carburetor must be contacted before the stop in the cockpit.
The stop in the cockpit must be contacted before the stop on the carburetor.
The throttle control is properly adjusted when neither stop makes contact.

What precaution should be taken when putting thread lubricant on a tapered pipe plug in a carburetor float bowl?

Put the thread lubricant only on the first thread.
Do not use thread lubricant on any carburetor fitting.
Engage the first thread of the plug, then put a small amount of lubricant on the second thread and screw the plug in.

Maximum power is normally considered to be developed in a reciprocating engine with a fuel/air mixture ratio of approximately

8:1.
12:1.
15:1

Excessively rich or lean idle mixtures result in

too rapid completion of combustion.
incomplete combustion.
incomplete cylinder scavenging.

PP Engine Fuel Systems

Jon K

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