M15.11 Flashcards
What are the 2 subsystems of the fuel system?
Fuel distribution
Fuel control
What are the 3 main tasks of the fuel distribution system?
Supply fuel to combustion chamber
Pressurise fuel
Heat fuel
What is the purpose of the LP pumps?
Ensures the HP pump doesn’t draw fuel from tanks by suction and prevents cavitation
How much pressure does the HP pumps provide?
900PSI
At what pressure do the over pressure relief valves operate at?
1250psi
Bypass oils is used for what?
To cool the IDG oil cooler
Why is cold fuel added to the hot bypass fuel?
So the fuel that enters the tank isn’t too hot
What is the hydro mechanical fuel control unit mounted to?
Engine fuel pump
How is control achieved in a hydro mechanical control unit?
By fluid pressure and mechanical components
What are the 2 types of fuel control unit?
Speed governed control unit (on old a/c)
Constant thrust control unit (modern a/c)
What does the speed generated control unit receive signals from?
N2 demand signal
N2 feedback signal
What does the constant thrust control unit receive signals from?
N2 demand signal
N2 feedback signal
N1 speed
Ambient pressure
Temp
What is the N2 speed signal transmitted by?
Via a mechanical drive shaft from the main fuel pump
What does the N1 signal come from?
The N1 speed sensor
What do temp signals come from?
Hydro mechanical temp sensor
FCU?
Fuel Control Unit
What are the 4 signals for the FCU?
Throttle demand signals
Speed feedback signals
Temp signals
Pressure signals
What are the 2 major sections of the FCU?
Fuel metering section
Computing section
What is the computing section of the FCU split into?
Governing section
Limiting section
What is the purpose of the metering section?
Ensures all the necessary fuel gets to the fuel nozzles
What is the purpose of the governing section?
Ensures selected power is controlled
What is the purpose of the limiting section?
Monitors the governing section and ensures engine operates within its safe limits
FADEC?
Full Authority Digital Engine Control
What is the FADEC?
A digital computer that has authority of engine control functions
What is the FADEC usually called?
ECU
FMU?
Fuel Metering Unit
Where is the FMU usually located?
In the fan case
What does the ECU do regarding thrust control?
Gives optimum thrust for all operating conditions
EIU?
Engine Interface Unit
