15_FUEL SYSTEM Flashcards
(22 cards)
Which tank is the primary source of fuel? Secondary?
Both engines are normally pressure fed from the CENTER tank until the center tank qty decreases to near 0 - THEN the respective MAIN tanks.
How many fuel pumps are in each tank? What are their power source?
2 AC powered fuel pumps
How are the AC powered fuel pumps cooled and lubricated?
2 AC fuel pumps are cooled and lubricated by fuel passing through the pump.
Which fuel pumps provide the highest pressure?
Center tank pumps - higher than main pumps (ensures center tank is used before mains)
What could cause a fuel pump LOW PRESSURE light to flicker?
when tank qty is low and airplane in a climb, descent or on ground with nose-down attitude.
When would the CENTER tank LOW PRESS lights possibly flicker?
When tank qty is low and airplane is in CRUISE.
- one pump may indicated low pressure before the other (normal)
- low pressure indication may occure AFTER center tank qty reads 0
How long could it take for the CENTER tank pump LOW PRESS light to flicker before the MASTER C and annunciator light illuminate?
flickering can continue for as long as 5 minutes before.
If the MAIN tank pump pressure is low, how do the engines get fuel?
they can suction feed which bypasses the pumps.
What are the concerns with suction feeding the engines vs positive pressure?
as airplane climbs, dissolved air is released from the fuel (due to decrease in air pressure) which may collect in fuel line and restrict fuel flow)
at high altitude this may cause thrust deterioration or engine flameout
This condition will go away eventually at top of cruise.
Can you suction DEFUEL?
Yes - the main tanks are capable of suction defueling.
What powers the Fuel crossfeed valve and from where?
the valve is a DC motor - BATT BUS
What does the fuel crossfeed valve do?
It allows fuel pressure from 1 tank to go to 2 engines. (will lead to fuel imbalance)
How many types of fuel SHUTOFF valves are there, where are they and what are they called?
2 types
Spar fuel so valve
Engine fuel so valve
both are DC motors
Spar - Hot Batt Bus
Eng Fuel - Batt Bus
What controls the fuel shutoff valves?
Both are controlled by the eng fire switch and the start lever. (which close)
When does the CENTER tank fuel scavenge jet pump operate and what does it do?
it operates automatically to transfer any remaining center tank fuel to MAIN TANK #1.
Fuel transfer BEGINS when main tank #1 qty is about 1/2 full AND the #1 main tank FWD switch must be ON.
Once the center tank fuel scavenge process begins, how do you stop it?
Once it begins it continues for the remainder of the flight and cannot be stopped.
Which tank is fuel temperature read from?
a sensor in the #1 MAIN tank (i.e. Left wing tank)
What is the power source of the fuel temperature gauge?
AC
When the AC fuel pumps are operating, where does the APU get its fuel?
If the pumps are NOT operating, how does the APU get fuel?
When AC pumps are operating - the APU gets fuel from the LEFT side of the fuel manifold. (ie Left tank OR left center tank pump)
If AC pumps are NOT operating, fuel is SUCTION fed from the #1 MAIN tank.
How many locations can you refuel / defuel? What type - gravity / pressure or both? Where is it located?
Single point - pressure refueling - right wing.
Where is the manual DEFUELING valve located?
located OUTBOARD of engine #2
What are the approx fuel qty in each tank and total?
Main - 9144#
Center - 28,973 #
Total - 47,261 #
