Fuel System Flashcards
If low fuel is detected in the left engine fuel feed line, which boost pump activates
Left and Right both come on.
How do you manually transfer fuel?
Select the MAN XFLOW AUTO OVERRIDE and then select the L or R XFLOW switchlight for the low side.
“press the light on the light side” The GRAVITY FLOW could also be pressed to allow fuel to freely move between tanks.
What is the maximum fuel imbalance allowed for takeoff and in flight, respectively?
300 lbs/800 lbs
What maintains fuel balance between the main tanks?
It is automatically controlled by a bi-directional crossflow pump.
The bi-directional XFLOW pump turns on and auto XFLOW begins when the fuel imbalance reached how many pounds?
200 pounds
How does center tank fuel arrive at the engine/APU
Transfer ejectors send it to the main tanks. Scavenge ejectors send it to the collector tanks. Main ejectors or boost pumps send it to the engines/APU.
All fuel tanks can be serviced by utilizing the overwing filler caps.
FALSE.
Powered crossflow can be used for takeoff if desired, but gravity crossflow cannot
False. Neither can be on for takeoff.
When will the main tank fuel quantity indications on ED2 and the fuel synoptic page turn amber?
Either main tank is less than 600 lbs.
Total fuel is less than 1200 lbs.
Fuel imbalance exceeds 800 lbs.
If the bi-directional XFLOW pump fails to turn on when the fuel imbalance reaches 200 lbs, the pilot must select gravity XFLOW to remedy the situation.
FALSE. Can use MAN XFLOW as well.
If there is a failure of motive flow, there is no way to get fuel into the collector tanks
FALSE. Gravity feed lines will keep the collector tanks full.
The minimum fuel temperature at the engine prior to takeoff is _______. The minimum bulk fuel and freezing temp for Jet A is
+5 deg C
-30 or -40 deg C.
How are the fuel tanks vented?
The tanks are vented to atmosphere by two NACA scoop vents on the underside of the wings. and climb vents. The tanks are positively pressurized.
What is used to back up the main ejectors to supply fuel to the engines?
Two electric boost pumps
If a significant (more than 800 lb) imbalance condition exists between the main tanks, what message will appear on the EICAS?
FUEL IMBALANCE
FUEL CAPACITIES
Pressure Fueling
7492/4610/7492. 19594 TOTAL
OVERWING 7290/7290. 700 7405/7405. 900 (BONUS...Why more in 900?)
Describe the fuel quantity gauging system?
A DC type capitance system indicates usable fuel.
Used for ground and in flight with a computer that compensates for pitch and roll.
Is there a manual way to check fuel?
yes 5 magnetic level indicators can be check on the exterior of the aircraft two under each wing and one under the fuselage.
Is dispatch authorized with the fuel quantity gauging computer inoperative?
no
Fuel quantities and pressures
see limitations slide deck
Where is the bulk fuel temperature sensor?
in the right wing tank
Where does the APU get fuel from?
A dedicated boost pump in the left collector tank
If the APU boost pump fails will the APU keep running?
Yes however it will not start unless the pump is operating
Will the main engines start without their respective boost pumps running?
yes
After turning on the boost pumps what do the switch lights look like?
The upper section of the switch lights illuminate “on” because low pressure is detected in the fuel lines and the pumps begin running
After starting both engines what do the fuel switchlights look like?
The lights extinguish because the pumps enter the standby mode. Motive flow supplies the fuel to the engines.
Will both boost pumps turn on if only one of the boost pump switchlights is pressed?
yes
How is the fuel warmed to reach 5 degrees or greater?
the fuel / oil heat exchanger
Describe the fuel check valve test.
Describe the path of fuel from the center tanks to the engines.
T transfer ejector from the center tank to the main tanks
S scavenge ejector from main tanks to collector tanks
M main ejectors from collector tanks to engines
aside from scavenge ejectors how does fuel enter the collector tanks?
One way flapper valves allow fuel to move by gravity into the collector tank
briefly describe the fuel system
one main tank in each wing an auxiliary tank in the center and two collector tanks which feed the engines located in the center tank. A FQGC Fuel Quantity Gauging Computer montiors fuel quantity, balance and temperature. It corrects for any imbalances through the use of a cross flow pump. Motive flow carries fuel from the wings to the engines for combustion
Describe how fuel is automatically transferred from the center tanks to the wings
When the wing tank falls below 93 percent the transfer ejectors in the center tank are activated until the main wing tank quantity reaches 97 percent
