M15.11

Question 1

What are the 2 subsystems of the fuel system?

Answer 1

Fuel distribution
Fuel control

Question 2

What are the 3 main tasks of the fuel distribution system?

Answer 2

Supply fuel to combustion chamber
Pressurise fuel
Heat fuel

Question 3

What is the purpose of the LP pumps?

Answer 3

Ensures the HP pump doesn’t draw fuel from tanks by suction and prevents cavitation

Question 4

How much pressure does the HP pumps provide?

Answer 4

900PSI

Question 5

At what pressure do the over pressure relief valves operate at?

Answer 5

1250psi

Question 6

Bypass oils is used for what?

Answer 6

To cool the IDG oil cooler

Question 7

Why is cold fuel added to the hot bypass fuel?

Answer 7

So the fuel that enters the tank isn’t too hot

Question 8

What is the hydro mechanical fuel control unit mounted to?

Answer 8

Engine fuel pump

Question 9

How is control achieved in a hydro mechanical control unit?

Answer 9

By fluid pressure and mechanical components

Question 10

What are the 2 types of fuel control unit?

Answer 10

Speed governed control unit (on old a/c)
Constant thrust control unit (modern a/c)

Question 11

What does the speed generated control unit receive signals from?

Answer 11

N2 demand signal
N2 feedback signal

Question 12

What does the constant thrust control unit receive signals from?

Answer 12

N2 demand signal
N2 feedback signal
N1 speed
Ambient pressure
Temp

Question 13

What is the N2 speed signal transmitted by?

Answer 13

Via a mechanical drive shaft from the main fuel pump

Question 14

What does the N1 signal come from?

Answer 14

The N1 speed sensor

Question 15

What do temp signals come from?

Answer 15

Hydro mechanical temp sensor

Question 16

FCU?

Answer 16

Fuel Control Unit

Question 17

What are the 4 signals for the FCU?

Answer 17

Throttle demand signals
Speed feedback signals
Temp signals
Pressure signals

Question 18

What are the 2 major sections of the FCU?

Answer 18

Fuel metering section
Computing section

Question 19

What is the computing section of the FCU split into?

Answer 19

Governing section
Limiting section

Question 20

What is the purpose of the metering section?

Answer 20

Ensures all the necessary fuel gets to the fuel nozzles

Question 21

What is the purpose of the governing section?

Answer 21

Ensures selected power is controlled

Question 22

What is the purpose of the limiting section?

Answer 22

Monitors the governing section and ensures engine operates within its safe limits

Question 23

FADEC?

Answer 23

Full Authority Digital Engine Control

Question 24

What is the FADEC?

Answer 24

A digital computer that has authority of engine control functions

Question 25

What is the FADEC usually called?

Answer 25

ECU

Question 26

FMU?

Answer 26

Fuel Metering Unit

Question 27

Where is the FMU usually located?

Answer 27

In the fan case

Question 28

What does the ECU do regarding thrust control?

Answer 28

Gives optimum thrust for all operating conditions

Question 29

EIU?

Answer 29

Engine Interface Unit