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Cat B- Mod 11 Aircraft Systems > 11.10 Fuel Systems > Flashcards

11.10 Fuel Systems Flashcards

1
Q

What does a fuel system usually consist of?

A

Tanks, pumps, filters, valves, lines and metering and monitoring devices.

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2
Q

What are rigid fuel lines made of?

A

Steel or aluminium alloy

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3
Q

What are the two basic types of fuel?

A

Reciprocating fuel (avgas)
Turbine fuel (Jet fuel)

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4
Q

How is AVGAS made?

A

Hydrocarbon compound refined from crude oil by a process called fractional distillation.

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5
Q

How is AVGAS different to jet fuel?

A

It is really volatile and extremely flammable with a low flash point.

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6
Q

What types of jet fuel are there?

A

Jet A1
Jet A
Jet B

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7
Q

What is the flashpoint of Jet A and A1?

A

43 to 65 degrees c

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8
Q

Which is better at the lower temp, A1 or A?

A

A1

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9
Q

What is the density of A1 and A at 15 degrees c?

A

0.81kg/litre

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10
Q

What three types of fuel tank are there?

A

Rigid removable
Bladder
Integral

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11
Q

What were many early fuel tanks made of?

A

Terneplate, a thin sheet of steel coated in lead or tin alloy.

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12
Q

What is a wet wing?

A

Integral tank design

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13
Q

What does NGS stand for?

A

Nitrogen generating system

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14
Q

What does the NGS do?

A

Designed to improve safety by reducing the risk of fuel tank explosions in aircraft. It does this by replacing oxygen in the fuel tanks with nitrogen

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15
Q

How does the NGS get nitrogen?

A

Extracted from the bleed air.

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16
Q

What four classifications of fuel leak are there?

A

Leak
Seep
Heavy seep
Running leak

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17
Q

How long is needed to monitor a leak?

A

30 mins

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18
Q

What area is classed as a stain?

A

19mm diameter

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19
Q

What area is classified as a seep?

A

19-38mm diameter

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20
Q

What area is a heavy seep?

A

38-101mm

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21
Q

What is SFAR 88?

A

Manages the safety, inspection and procedures of the fuel system and its components.

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22
Q

What is CDCCL?

A

Critical design control configuration limitations.

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23
Q

What does CDCCL control?

A

Refers to a feature of the fuel system design, for which integrity must be maintained to ensure that unsafe conditions do not develop.

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24
Q

What kind of components may you find as part of CDCCL?

A

Bonding leads
Harnesses and probes
Pumps
Access panels

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25
Q

Are CDCCL’s mandatory and how can they be changed?

A

Yes, only with approval from the NAA

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26
Q

What must the concentration of fuel vapours be kept below?

A

The lower explosive limit.

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27
Q

What is FQIS?

A

Fuel Quantity Indicating System

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28
Q

What four options does the selector valve have in a gravity feed system?

A

Shut off to the engine
Feed from the right wing
Feed from the left wing
Feed from both wings

29
Q

What are large aircraft fuel systems split into?

A

Storage
Vent
Distribution
Feed
Indicating

30
Q

What is a wobble pump?

A

Old school hand operated pump that delivers fuel backing up the engine driven pump.

31
Q

What is the disadvantage of a wobble pump?

A

It requires fuel lines to be run through the flight deck.

32
Q

How do vane type pumps regulate flow?

A

Adjustable pressure relief component

33
Q

Centrifugal pumps are normally in the tank, what do they need if they are outside the tank?

A

Removal valve so that the pump can be removed without draining the fuel.

34
Q

Depending on aircraft design what is the centrifugal boost pump used for?

A

EDP

35
Q

What are fuel pumps cooled by?

A

The fuel flow

36
Q

What do flapper valves allow?

A

Allow fuel to flow inboard to the pump.

37
Q

What does an ejector pump do?

A

Ensure the pump always has liquid fuel at the inlet.

38
Q

What is installed between the supply tanks and the engine fuel system to protect the engine-driven fuel pump and various control devices?

A

Low pressure filter

39
Q

What are the three most common types of fuel filter?

A

Micron
Wafer screen
Plain screen

40
Q

What size particles can a micron filter remove?

A

10-25 microns

41
Q

What is the downside of micron filters?

A

They are easily clogged therefore a bypass is required.

42
Q

What are the two weight limits that must not be exceeded?

A

Max take off
Max structural landing weight

43
Q

What are fuel vent systems designed to do?

A

Relieve pressure in the fuel tanks and to allow proper flow of fuel.

44
Q

What does the vent system maintain the pressure at?

A

Atmospheric

45
Q

What can under pressurisation of the fuel tanks cause?

A

Component malfunction and engine fuel starvation.

46
Q

What does not happen in an inflight fuel transfer?

A

Fuel is not moved from one tank to another, instead it is used to feed the engine until the levels are corrected.

47
Q

For a ground fuel transfer what must the engineer do?

A

-Open the x feed valves
-Switch on boost pumps in tank which fuel is leaving
-Open defuel valve
-Open refuel valve for tank that is receiving

48
Q

In a ground fuel transfer what does opening the defuel valve achieve?

A

Connects the engine feed manifold to the refuel manifold.

49
Q

Fuel cross feed valves are motor actuated, what main parts do they have?

A

Valve body
Adapter and shaft
Actuator

50
Q

What is the actuator in the fuel x feed valve?

A

28V DC

51
Q

How many fuel flow indicators are there?

A

One per engine

52
Q

Where is the temp sensor usually located?

A

Main fuel tank

53
Q

Where are low pressure sensors located?

A

Boost pump inlet lines

54
Q

What is a ratiometer type fuel quantity sensor?

A

The most common, uses a DC loop which utilises variable resistance to drive the indicator.

55
Q

How do capacitance type fuel quantity sensors work?

A

Wired in parallel, as the level changes so does the capacitance of each one. A computer then sums the individual capcitances.

56
Q

What is used to match the capacitance output with the pre calibrated indicator?

A

A trimmer

57
Q

The amount of electricity stored in a capacitor depends on what 3 things?

A

Area of the plates
Distance between the plates
Dielectric constant

58
Q

What is meant by the ullage?

A

Emptiness of the tank

59
Q

What calculations does an ultrasonic fuel quantity system use?

A

Fillage = Total height - ullage

60
Q

Valve in transit lights have what lighting states to indicate position?

A

Abnormal condition- Dim
Transit- bright
Normal- off

61
Q

What two methods of refuelling are there?

A

Gravity overwing
Pressure

62
Q

What are the main components of a typical refuelling system?

A

Couplings
Valves
Manifold
Diffusers

63
Q

What three modes of pressure refuelling are there?

A

Manual
Automatic
Override

64
Q

What is key before refuelling in manual mode?

A

Calculate the distribution

65
Q

What pressure is pressure defuelling?

A

25 psi to 50psi

66
Q

When will the FCMC start an aft transfer?

A

Landing gear and slats retracted
Trim tank not full
Inner tank above 6250kg

67
Q

When will the aircraft do an automatic fuel transfer forward?

A

CG equals target
Inner tank less than 4000kg

68
Q
A

Cat B- Mod 11 Aircraft Systems (28 decks)

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