Fuel System Flashcards
Fuel Tanks
Each wing tank holds 4960lbs. (758gal.)
Total fuel 9920lbs. (1516gal.)
Additional volume allows for 2% thermal expansion.
Fuel Vent System
Tanks
- ensures positive pressure
- vents each tank to the atmosphere via a vent duct and vent float valve to a 100L surge tank where it is directed back to the wing tank
Wing Center Box
- stores no fuel
- vents and drains to the atmosphere to prevent vapor buildup
Engine Shut Down With Electric Pump Running
Both fuel engine electrical pumps push buttons are pressed IN and green RUN lights illuminate. The electrical pumps are energized and begin to supply fuel to engines. The FEED LO PR amber light extinguishes when the pressure is > 4 psi on the line. At the same time, the feeder jet pump is activated by the electrical pump output pressure, to supply and maintain the feeder tank full.
Engine Running / Normal Operation of the Fuel System
After engine starting, the flow from return line of the HMU opens the Motive Flow Valve in order to supply the Engine Feed Jet Pump. The Engine Feed Jet Pump begins to operate by driving fuel from the feeder tank. At the same time, it supplies the Feeder Jet Pump. When the Engine Feed Jet Pump outlet pressure reaches 8.5 PSI, the electrical pump is de-energized after 30s time delay. In normal operation of the fuel system, the engine is only supplied by the Engine Feed Jet Pump and the electrical pump is de-energized.
Conditions to energize the electrical pump
– Cross feed operation
– Engine Feed Jet Pump oulet pressure drops below 5 psi
– Low Level
Cross Feed Procedure
Cross feed valve could be used to supply an engine from the opposite tank. The cross feed is not used to tranfer fuel from one tank to the other tank. With the Xfeed valve push button pressed IN, the valve opens, green flow bar is horizontal. Both electrical pump are energized. By selecting OFF the corresponding PUMP push button, the electrical pump is de-energized and the motive flow valve is supplied to close. The engine is fed through the opposite tank.
Engine Feed Jet Pump Low Pressure
If the jet pump pressure drops below 5psi, the electric pump is automatically activated to supply the engine.
Low Fuel Level
When the low level is triggered on one tank, its electrical pump is automatically activated.
Two cases of low level:
-LO LVL with fuel quantity indicator below 352lbs.
-Feeder tank not full due to a failure of the feeder jet pump. In this condition, the fuel is transfered from the main tank to the feeder tank through the flappers.
FEED LO PRESS light
Delivery pressure below 5psi
Refuel/Defuel System
Maximum refueling pressure is 50psi
Maximum defueling pressure is -11psi
Refueling valves may be manually operated with not electrically powered
Fuel System General
The fuel system includes
- 2 tanks with 1 electric pump and 1 jet pump in each
- the vent system
- the fuel quantity indicating system
- the pressure fueling system
