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CAA Module 15 > Module 15.11 Fuel systems > Flashcards

Module 15.11 Fuel systems Flashcards

1
Q

Quantity of fuel supplied must be automatically adjust for what?

A

Changes in ambient temperature or pressure

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2
Q

What are the 3 GTE fuel control systems?

A
  • Hydromechanical
  • Hydromechanical/electronic
  • FADEC
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3
Q

If fuel flow increases too, rapidly an over rich mixture can occur, this can cause what?

A
  • Rich blowout
  • Compressor stall
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4
Q

In the dual mode of the hydromechanically/electronic metering system, fuel flow is set by what?

A

Servo motors

Input + output are electronic

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5
Q

The fuel metering system must be able to do what?

A

Increase and decrease power

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6
Q

To provide the correct fuel for the engine, hydromechanical fuel controls have what two sections?

A

Computing and metering

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7
Q

A pure hydromechanical control system has no what? and is driven by what?

A
  • Electronic interface
    — accessory gearbox
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8
Q

What is the function of the engine fuel system?

A
  • Pressurise the fuel
  • Meter the fuel flow
  • Deliver atomised fuel to the combustion chamber
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9
Q

Fuel flow is controlled by what in hydromechanic control?

A

Hydromechanical fuel control assembly

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10
Q

The Hydromechanical fuel control assembly contains what two parts?

A
  • Fuel shut off section
  • Fuel metering section
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11
Q

The total engine fuel and control system contains what components?

A
  • Vane fuel pump
  • Filter bypass valve
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12
Q

What is the mechanical indication of bypass valve opening?

A

Pin extended

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13
Q

What does the EFCU stand for?

A

Electronic Fuel Control Unit

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14
Q

What does the EEC system consist of? (Hydromechanical)

A
  • Hydromechanical fuel control
  • EFCU
  • Aircraft mounted power lever angle (PLA) pentiometer
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15
Q

What are the engine generator control signals? (Hydromechanical)

A
  • Fan spool speed
  • Gas generator spool speed
  • Inner turbine temperature
  • Fan discharge temperature
  • Compressor discharge pressure
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16
Q

Where is the EFCU mounted?

A

Airframe

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17
Q

What does the PLA pentiometer transmit?

A

Electric signal of throttle lever position to the EFCU

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18
Q

The FADEC system uses electronic sensors to provide what?

A

Information to the EEC

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19
Q

What does the EEC do with the FADEC information?

A

Calculates amount of fuel flow by adjusting the fuel metering valve

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20
Q

What can be said about the two electronic channels in the EEC?

A
  • Physically separate
  • Cooled by convection
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21
Q

What provides the throttle lever position to the EEC in the FADEC system?

A

Throttle lever angle resolver

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22
Q

What does the cross talk logic do?

A

Compares data from channel A and B

23
Q

What does the primary EEC channel control?

A

All the output drivers

24
Q

Where is the fuel metering unit mounted in the FADEC system?

A

Front face of the gearbox and to the front of the fuel pump

25
Q

The EEC provides position feedback for engine compartments by using what?

A
  • RVDT
  • LVDT
  • Thermocouples
26
Q

What does the programming plug do in FADEC?

A

Selects the proper software in the EEC for the engine thrust rating

27
Q

What is the primary and secondary fuel system?

A

Primary - Stores fuel
Secondary - Supplies fuel to engine

28
Q

A non-constant displacement pump (Centrifugal) is used at inlet of the EDP to provide what?

A

Provide positive flow to the second stage of the pump (HP pump)

29
Q

How is the fuel pump lubricated?

A

Fuel passing through the pump

30
Q

Where is the LP filter?

A

Before the pump

31
Q

Where is the HP filter?

A

After the pump

32
Q

What are the 3 most common types of filter?

A
  • Micron filter
  • Wafer screen filter
  • Plain screen mesh filter
33
Q

What filter has the best filtering action?

A

Micron filter, 10-25 microns

34
Q

What is the most common filter?

A

200 mesh and 35 mesh micron filters

35
Q

GTE fuel systems are very susceptible to what?

A

Ice in the fuel filters

36
Q

What does the fuel manifold do?

A

Distributes the fuel to the individual fuel nozzles

37
Q

What manifold are most common on GTE’s?

A

Single-fuel

38
Q

Where is leaked fuel caught by the shroud drained to?

A

Engine drain mast

39
Q

What are the methods of leak protection?

A
  • Shrouded connection
  • Double sealed connection
40
Q

On older aircraft they have how many supply lines and manifolds?

A

Two

41
Q

What does the secondary manifold supply fuel to?

A

Secondary fuel nozzles

42
Q

What are the two nozzle types?

A
  • Simplex
  • Duplex
43
Q

Duplex nozzles require what?

A

A duplex manifold

44
Q

How can nozzles be mounted?

A

Internally or externally

45
Q

What is the drawback of simplex nozzles?

A

Only good atomisation in a small fuel flow range

46
Q

Using simplex, what is required for good atomisation across a wide fuel range?

A
  • One set with a small discharge orifice (start to idle)
  • Secondary set with large discharge orifice (idle to max)

(Old technology)

47
Q

Duplex nozzles combine what?

A

Two nozzles in one component

48
Q

Why is a check valve used in the fuel nozzle?

A

Prevent carbon formation

49
Q

Fuel that is not required returns to the fuel pump via what line?

A

Bypass return line

50
Q

Where is the fuel flow indicator located?

A

In between the Fuel control unit and the nozzles

51
Q

Fuel to the LP pump is what psi?

A

40 psi

52
Q

Fuel after the LP pump is what psi?

A

175 psi

53
Q

Fuel after the HP pump is what psi?

A

1250 psi

54
Q

Why is bypass return fuel mixed with LP pump outlet fuel in the recirculating valve before entering the engine?

A

To cool it down

CAA Module 15 (18 decks)

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