5. Fuel System Flashcards
How are the fuel gauges calibrated?
To indicate usable fuel
Which fuel tank supplies which engine?
FWD tank supplies fuel to right and the AFT tank supplies fuel to the left engine
If AC power is lost, what will fuel gauges indicate?
Needles will continue indicating amount they indicated at the time of the AC power loss
What fuel pressure output must a boost pump fall below to cause a caution light to illuminate?
2 psi
When should fuel be dipped?
At least 15 minutes after shut down with aircraft level and boost pumps off
What must be available for shutoff valves to function?
DC power
What does each tank consist of and how many probes?
1 collector and 3 feeder cells. One capacitance probe per cell
How are fuel tank vents set up?
Each cell has two vents, left and right, all connected together to single left/right wing vents
What is the maximum fuel imbalance?
No limit. Only C of G is applicable
What is the boost pump nominal output?
450lbs per hour at a nominal pressure of 22 psi
What is the secondary function of the boost pumps and how is it accomplished?
To transfer fuel from feeder cells to their respective collector cell.
Excess boost pump output is routed through a venturi, known as an ejector. After going through this ejector the fuel is returned to the collector cell. The created venturi effect draws fuel from the feeder cells into the common manifold along with the motive flow fuel. The combined fuel then flows into the collector cell.
What happens when fuel selector switch is moved to BOTH ON FWD position?
(1) crossfeed valve opens, which allows either tank to feed both engines.
(2) number 2 pump in forward tank turns on and number 1 pump in aft tank turns off (pressure output from forward tank only)
Why must boost pumps be turned on prior to and kept running while draining fuel from the fuel filter?
To prevent air from entering the system
If boost pump 1 fails, boost pump 2 automatically activates. Why must boost pump 2 not be manually switched ON?
It could result in having 3 pumps running at the same time.
With crossfeed valve open both engines take whatever pressure output is higher. With pressure from both tanks present there is no way of knowing what side has the highest pressure output, so a situation could arise where you think you are drawing fuel from one tank when you may be drawing fuel from other.
What does fuel quantity gauge indicate when TEST is selected?
Falls to 0, then back to actual quantity when released.
What is the usable capacity of the AFT tank?
197.8 US GAL (1338.2lb JET A1)
What is the usable capacity of the FORWARD tank?
181.2 US GAL (1232.2lb JET A1)
What happens when the boost pump TEST is actuated?
Failure of boost pump 1 is simulated. The BOOST PUMP 1 PRESS light should illuminate and boost pump 2 should begin to operate.
What does it mean if both boost pump lights for the same tank illuminate? What action should be taken?
Two possible problems:
Failure of the number 1 pump along with a failure of the changeover system or it could be a double pump failure. The two lights that are illuminated are telling you that there is <2psi at either pump.
Select STBY BOOST PUMP EMER switch ON. If no.2 caution light extinguishes the no.2 pump has manually energized (changeover system failed).
If no.2 light does not extinguish this confirms failure of both pumps.
What does a BOOST PUMP 1 CAUTION LIGHT mean?
Boost pump 1 has failed. Boost pump 2 in the same fuel tank will switch on automatically. The number 2 caution light will come on momentarily but will go out once number 2 fuel boost pump pressure switch senses the rising pressure.
