Answers - Fuel Systems


Fill in the Blanks

1. hard engine starting, slow warm‐up, slow
2. explode, detonate
3. vaporizes, carburetor
4. 30‐40 °F, humid
5. explosion, pressure, temperature
6. lower, higher
7. main, auxiliary, surge
8. rigid removable tanks, bladder tanks, integral fuel
9. sump
10. wiring
11. gate, plug
12. quickly
13. engine driven fuel pump
14. positive, vapor lock
15. vane type
16. crossfeed system, fuel transfer
17. large, fuel system
18. micronic, 10‐25
19. fuel heaters
20. Direct current (DC)
21. Stain, seep, heavy seep, running
22. 1/1/2 inches, 4 inches
23. dried and ventilated, combustible gas indicator
24. cloudy
25. Over the wing, pressure refueling


TRUE or FALSE

1. true
2. false; turbine fuel has a higher flash point than AVGAS
3. true
4. false; higher cylinder head temperature
5. true
6. false; Jet A is the most common
7. false; pump feed system
8. true
9. true
10. false; aircraft equipped with integral fuel tanks have fuel vent systems and fuel jettison systems dump fuel when the take off weight is higher than the landing weight
11. true
12. false; to the engine driven fuel pump
13. false; variable displacement pump
14. false; lowest part of the tank
15. true
16. true
17. false; electronic fuel quantity systems have no moving part which is one of their advantages
18. true
19. false; they measure fuel mass
20. true
21. false; must be repaired before the next flight because vapors in these areas could cause a fire or explosion
22. true
23. false; organisms do not grow in AVGAS, only turbine fuel
24. true
25. true

Knowledge Application

1. If take off weight is higher than the landing weight, in an emergency these aircraft need to reduce the weight to a specified landing weight.
2. Rigid removable cell, bladder‐type cell, integral fuel cell
3. The structure of the cavity that the cell fits into.
4. alerts the flight crew that there may be danger of ice crystals forming in the fuel.
5. To provide an interconnected fuel system so that fuel can be fed from various tanks to any engine.
6. crossfeed, transfer, ON or OFF
7. compare the fuel quantity in the tank with the indication of the electronic fuel quantity system.
8. An underwing or single‐point pressure fueling system.
9. reduces fueling time, eliminates aircraft skin damage, and reduces chances of contamination.
10. The tank is pressurized with up to 1/2 psi air pressure and liquid soap is added to detect leaks.
11. An internal component fuel leak (shutoff valve, selector valve, or crossfeed valve).
12. Sight glass, mechanical, electrical, and electronic.
13. It measures by weight instead of volume.
14. resist surging from changes in the attitude of the aircraft.
15. allow water and sediment to settle to the drain point.
16. drain the water out of the tanks.


Multiple Choices

1. c
The fuel jettisoning system of an aircraft is usually divided into two separate, independent systems, one for each wing, so that lateral stability can be maintained by jettisoning fuel from the "heavy" wing. Each wing contains either a fixed or an extendable dump chute, depending upon system design.

2. a
If an aircraft's landing weight is less than its take-off weight a means must be provided to jettison fuel to achieve a safe landing weight.

3. b
According to FAR 23, both of the statements in the question are true. The fuel jettisoning valve must be designed to allow flight personnel the ability to close it during any phase of the jettisoning operation. In addition, the fuel must discharge clear of any part of the airplane.

4. c
The fuel jettisoning system is usually divided into two separate, independent systems, one for each wing, so that lateral stability can be maintained by jettisoning fuel from the "heavy" wing.

5. b
According to FAR 23, a fuel jettison system is required for transport category and general aviation aircraft if the maximum takeoff weight exceeds the maximum landing weight.

6. b
Systems operation may vary from aircraft to aircraft, but the fuel boost pumps alone, or a combination of boost pumps and gravity will be used to jettison fuel.

7. a
There is a fuel dump limit-valve in each fuel tank that will shut off the flow if the pressure drops below what is needed to supply the engine with adequate fuel. It will also shut off the dump valve when the level in the tank gets down to the preset dump shutoff level.

8. b
On a sweptback wing airplane, defueling procedures usually dictate that the outboard wing tanks be defueled first. If the inboard tanks are defueled first, the weight of the fuel in the outboard tanks can cause a rearward shift of the center of gravity that can cause the aircraft to tip back on to the tail.

9. b
Cross-feed valves are used to allow fuel to either be moved from tank to tank, or from either tank to either or both engines. The pump crossfeed in figure 1 is used to route fuel from either tank to either or both engines.

10. b
Cross-feed valves are used to allow fuel to either be moved from tank to tank, or from either tank to either or both engines.

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