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M15 > 15.11 Fuel System > Flashcards

15.11 Fuel System Flashcards

1
Q

Fuel systems must be able to respond to rapid acceleration demands. But if fuel flow increases too rapidly what can happen?

A

Rich blowout or compressor stall.

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2
Q

What are the 3 types of fuel controller systems?

A

Hydro mechanical.
Hydro mechanical/electronic.
FADEC.

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3
Q

What does FADEC fuel control system use?

A

Electronic sensors.

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4
Q

What are the 2 sections of the hydro mechanical fuel control system?

A

Computing and metering.

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5
Q

Does hydro mechanical fuel control system have an electronic interface?

A

No

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6
Q

What are the negatives of the hydro mechanical fuel control system?

A

Very complicated.
Fuel metering is not as accurate as electronic type.

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7
Q

What does a hydro mechanical/electronic fuel control system use?

A

Remotely located Electronic Engine Control (EEC)

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8
Q

What are the 3 functions of the engine fuel system?

A

Pressurise fuel.
Meter fuel.
Deliver atomised fuel.

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9
Q

What are the 2 sections of a hydro mechanical/electronic fuel control asssmbly?

A

Fuel shut off.
Fuel metering.

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10
Q

What is the purpose of the vane fuel pump assembly in a hydro mechanical/electronic system?

A

To provide high pressure fuel.

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11
Q

What does the filter bypass have to provide excessive differential pressure?

A

An integral differential pressure indicator.

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12
Q

What provide the fuel metering function of the EFCU in a hydro mechanical/electronic system?

A

Hydraulically Metering Unit.

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13
Q

What does the hydro mechanical/electronic EEC system consist off?

A

Hydro mechanical fuel control/ HMU.
EFCU
Power Lever Angle (PLA) potentiometer.

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14
Q

What transmits electronic signals to the EFCU in a hydro mechanical/electronic system?

A

PLA potentiometer.

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15
Q

Where is the EFCU located?

A

Remotely located mounted on the aircraft.

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16
Q

What does the EEC do in a FADEC fuel control system?

A

Calculates the amount of fuel by adjusting the Fuel Metering Valve.

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17
Q

In a FADEC system, the EEC houses 2 electronic channels ( A + B ). What can be said about them?

A

Separated internally.

Cooled by convection.

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18
Q

What supplies EEC in the FADEC system?

A

Throttle Lever Angle resolver.

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19
Q

In a FADEC system, how do the 2 electronic channels compare their data?

A

Crosstalk logic.

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20
Q

What system has a Fuel Metering Unit( FMU)?

A

FADEC system only.

21
Q

Where is the FMU mounted?

A

Mounted on gearbox front face, and attached to fuel pump front.

22
Q

In a FADEC system, How does the EEC receive position feedback?

A

RVDT.
LVDT.
Thermocouples.

23
Q

What is the difference between the primary and secondary fuel system?

A

Primary= stored fuel.
Secondary = supplies fuel.

24
Q

What is the pressure of fuel at the LP fuel valve?

A

40 psi.

25
Q

What is the pressure of fuel at the LP fuel pump?

A

175psi.

The LP fuel pump increases pressure.

26
Q

What can the oil cooler also be known as ?

A

Fuel heater.

27
Q

What can be said about the Fuel Control Unit?

A

It gets more fuel than necessary to be ready for acceleration.

28
Q

What returns excess fuel from the FCU?

A

Bypass return line.

29
Q

What is the pressure of fuel after the Pressure Relief Valve?

A

900 psi.

30
Q

What does the Fuel Recirculation Valve do?

A

It mixes cold fuel from tank with hot fuel then returns it to the tank

31
Q

What does the Fuel Flow Transmitter do?

A

Measures fuel flow.

32
Q

What is the purpose of a servo fuel heater?

A

Secondary heating if ice is still present in fuel.

33
Q

Why must the Engine Driven fuel pump be capable of maximum flow?

A

For satisfactory nozzle spray and accurate fuel regulation.

34
Q

What are the 2 types of EDPs?

A

Constant displacement.

Non- constant displacement/ centrifugal.

35
Q

How is the fuel pump lubricated?

A

By fuel passing through the pump.

36
Q

Where is the LP filter located?

A

Between supply tank and engine fuel system.
(Before LP pump)

37
Q

Where is the HP filter located?

A

Between the fuel pump and fuel control.
(After HP pump)

38
Q

What are the 3 types of filters?

A

Micron,
Wafer screen,
Plain screen.

39
Q

What filter offers the greatest filtering action?

A

Micron filter.
10-25 microns.

40
Q

What is the most used filter?

A

200 and 35 mesh micron filter.

41
Q

On what engines are single fuel manifolds used?

A

Modern GTE.

42
Q

What is the purpose of shrouds?

A

To catch fuel leaks and drain them to the engine drain mast.

43
Q

What are the 2 methods to protect fluid line connections?

A

Shrouded lines.
Double sealed lines.

44
Q

How many lines and manifolds do old GTEs have?

A

2 fuel supply lines and 2 manifolds.

45
Q

What manifolds do duplex and simplex nozzles require?

A

Duplex= dual.
Simplex= single.

46
Q

What’s the negative of simplex nozzles?

A

Only give good atomisation in a small fuel flow range.

47
Q

When 2 sets of simplex nozzles are used, what’s the difference between the 2?

A

Primary = small discharge orifice for engine start up.

Secondary = larger discharge orifice for acceleration up to max power.

48
Q

What does the check valve prevent as well as backflow?

A

Carbon formation

49
Q

How does a dual flow nozzle differ from 2 single flow nozzle?

A

It combines 2 nozzles into 1 component instead of 2.

M15 (18 decks)

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