Fuel System Flashcards
Describe the boost pump
DC electric, centrifugal-type boost pump. Send fuel to:
- respective engine-driven pump
- transfer ejector pump
- fuel transfer balancing system to opposite sump
How much total usable fuel?
3,960 lbs or 586 gallons. (293 gallons per wing)
4710 (CJ3)
How many ejector pumps and how do they work?
2
- powered by motive flow from engine-driven pump (Venturi principle)
- transfer ejector pump takes fuel from lowest point of the tank.
What does the fuel transfer switch control?
Fuel transfer valve
How is fuel heated?
Engine oil
When are the fuel firewall shutoff valves closed?
Engine fire or testing.
When is the motive flow shutoff valve closed?
During start below 45% N2. Otherwise open
Which position of the boost pump switch will cause the boost pump to operate automatically?
NORM position
-ON will make it operate continuously and OFF will shut it off
How is fuel quantity sensed?
14 capacitance probes (seven per tank)
What does L or R F/W SHUTOFF annunciator indicate?
Both fuel and hydraulic firewall shutoff valves are closed. (When L or R engine fire switch is pushed)
When does L or R FUEL LOW PRESS annunciator come on?
When fuel pressure goes below 5 psi or above 7 psi
When does L or R FUEL LOW LEVEL annunciator come on?
When float switch senses only 200lbs left (+/-10lbs) (also, turn boost pump on)
When does L or R FUEL GUAGE annunciator come in?
If fuel quantity signal conditioner detects a fault
When does L or R FUEL FLTR BYPASS annunciator come on?
Fuel is bypassing the filter. Land as soon as practical.
What five parameters are sensed by FCU (hydromechanical fuel control unit)?
- P3 or compressor discharge pressure
- Pa or ambient pressure Tt2
- compressor inlet temperature
- N2 rpm
- throttle position
