Aircraft Fuel Systems

Question 1

Why do some aircraft have fuel jettison systems?

Answer 1

To allow the crew to reduce the weight of the aircraft down to or below the maximum allowable landing weight.

Question 2

Is there any reason why a fuel jettison system might be required on a small aircraft?

Answer 2

Yes, if the maximum takeoff weight exceeds the maximum allowable landing weight, a jettison system would be required.

Question 3

What are some other names for a single-point fueling system?

Answer 3

An underwing or pressure fueling system.

Question 4

Why do multi-engine airplanes have fuel crossfeed systems?

Answer 4

To allow any engine to draw fuel from any tank.

Question 5

The fuel selector valve for a multi-engine aircraft must have at least three positions. What are they?

Answer 5

ON, OFF, and Crossfeed.

Question 6

Why do some fuel tanks have internal baffles?

Answer 6

To resist fuel surging or sloshing caused by changes in the attitude of the aircraft.

Question 7

What are the two types of fuel cells?

Answer 7

Integral or wet wing fuel cells, and bladder-type fuel cells.

Question 8

What does the term “wet wing” mean?

Answer 8

It means that sealed portions of the aircraft wing structure form the fuel tank(s).

Question 9

How is the weight of the fuel supported when bladder-type fuel cells are used?

Answer 9

The bladder is supported by the aircraft structure which contains it.

Question 10

Why do turbine-engine aircraft have fuel temperature indicating systems?

Answer 10

To allow the crew to determine if the fuel is cold enough to produce a danger of the formation of ice crystals.

Question 11

Name four types of fuel quantity gauging systems currently in use.

Answer 11

Sight gauges, mechanical, electric, and electronic gauges.

Question 12

Why are electronic (capacitance-type) fuel quantity indicating systems more accurate than other types?

Answer 12

They measure the mass of the fuel instead of the volume.

Question 13

What are drip gauges and sight gauges?

Answer 13

Underwing, bayonet-type fuel gauges.

Question 14

What is the purpose of an in-transit light associated with an electrically operated fuel tank shutoff valve?

Answer 14

To provide an indication that the valve is in motion between one position and another.

Question 15

For what reason is a fuel jettison system usually divided into two separate, independent systems, one for each wing?

Answer 15

To help maintain lateral stability by jettisoning fuel from a heavy wing if necessary.

Question 16

What procedures should be followed regarding gaskets and seals when replacing fuel system components?

Answer 16

All old gaskets and seals should be replaced with new ones.

Question 17

Is it possible for a fuel system to develop a leak that has no visible evidence such as a stain or spot, and if so, how?

Answer 17

An internal component such as a valve could develop a leak.

Question 18

How is a fuel tank checked for leaks following a patch or welded repair?

Answer 18

The tank is slightly pressurized with air and the repaired area is leak-checked with a soap and water solution.

Question 19

Name some advantages of a single-point fueling system.

Answer 19

It reduces fueling time, reduces chances for contamination and fire, and eliminates damage to the aircraft skin.

Question 20

Why should you wait for a period of time after fueling an aircraft before checking the fuel sumps?

Answer 20

To allow time for water and contaminants to settle to the drain point.