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M15 > M15.11 > Flashcards

M15.11 Flashcards

1
Q

What is the job of a primary fuel system?

A

It is the system of storing fuel

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2
Q

What is the job of a secondary fuel system?

A

It is the fuel system that goes to the engine

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3
Q

The engine fuel system can be split into two subsystems, what are these?

A

Fuel distribution and fuel control

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4
Q

The engine fuel distribution system has three main tasks, what are they?

A
  • to safely supply fuel
  • to pressurise the fuel to be vaporised
  • to heat the fuel
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5
Q

What is the job of the low pressure fuel pump?

A

To increase the fuel pressure that comes from the tanks

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6
Q

What is the job of the high pressure fuel pump?

A

Increase the pressure to the high level needed for vaporisation in the combustion chamber

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7
Q

What is the job of a pressure relief valve?

A

To protect the pump from over pressurisation by releasing pressure

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8
Q

What is the job of a fuel control unit?

A

To regulate the amount of fuel needed in the combustion chamber. There is also a shut off valve to the fuel nozzles in emergency’s

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9
Q

What is can be added to be absolutely free of ice in the servo fuel?

A

Servo fuel heater

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10
Q

Why is a fuel flow transmitter used?

A

It measures the actual fuel flow and sends signals to the cockpit

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11
Q

What is the advantage of having the oil cooler downstream of the high pressure pump?

A

Less external fuel lines

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12
Q

What pressure does a low pressure fuel pump go up to?

A

175psi

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13
Q

Why is the low pressure fuel pump pressurised?

A

So the high pressure stage doesn’t need to suck fuel through and to prevent cavitation

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14
Q

What is the pressure at the high pressure fuel pump at max engine speed?

A

900psi

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15
Q

At what pressure does the overpressure relief valve open?

A

1250psi

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16
Q

What can the bypass fuel be used for?

A

To cool the IDG oil (cold fuel may be need to cool the now hot fuel down to prevent thermo shock)

17
Q

Where can the fuel control unit of an engine be found?

A

Usually mounted to the engine fuel pump on the accessory gearbox

18
Q

What type of component is the fuel control unit?

A

Hydrochemical (all control functions are done by fluid pressures and mechanical components)

19
Q

What are the two types of fuel control units?

A
  • speed governed fuel control units (old)

- constant thrust fuel control units (new)

20
Q

What does a speed governed fuel control units use for steady state fuel metering?

A

N2 speed

21
Q

What does a constant thrust fuel control unit use for steady state fuel metering?

A

N1 speed, ambient pressure and temperature

22
Q

How is the thrust lever signal out putted?

A

Rack and pinion or by rods and levers

23
Q

How is the N2 speed feedback signal transmitted?

A

Via a mechanical drive shaft from the main fuel pump

24
Q

How is the N1 speed feedback signal transmitted?

A

Comes from a hydrochemical N1 speed sensor

25
Q

Where do temperature signals like CIT or fan inlet temperatures come from?

A

Hydro mechanical temperature sensors

26
Q

What does FADEC stand for?

A

Full authority digital engine control

27
Q

What is the computer called in a FADEC system?

A

Electronic control unit or the electronic engine control

28
Q

What is the second main component of the FADEC system?

A

Fuel metering unit

29
Q

What is the fuel metering unit also known as?

A

Hydro mechanical unit

30
Q

The fuel metering unit and the hydro mechanical unit don’t have control in them, whys this?

A

Because they only receive from the electronic control unit not control

31
Q

Where is the electronic control unit located?

A

On a fan stator case of the engine

32
Q

What is needed for correct operation of the electronic control unit?

A

A demand signal from the thrust lever in the cockpit

M15 (15 decks)

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