Fuel System Flashcards
How many fuel tanks
3, left right and center
They can all be fueled through…
The single point adapter
Which tanks can be gravity fueled?
Only left and right
Can the fuel in the center tank go directly to the engines?
No, it has to go to the left or right wing tank first
Croosflwo vs transfer
Crossflow = balancing the weight Transfer = flowing fuel from one place to another
What tank must all fuel flow through
Collector tanks
Which tank does the APU draw fuel from?
The left collector tank. This dads to the left tank often having less fuel.
Is there a true left and right fuel tank?
Negative. The inside of the wings are the tanks and are sealed with a fuel resistant sealant.
What are flapper valves
One way valves on the wing ribs that don’t allow the fuel to flow towards the wing tip during wing low maneuvers.
Pressure relief valve
Automatically evacuates fuel if overfilled. Spring loaded. Located on the bottom midpoint of each wing.
What do the NACA scoops do
Prevent ice build up and allows the tanks to vent.
Fuel system computer (FSC)
Dual-channel computer that monitors and controls the fuel system
Only one channel is active at a time
Engine driven fuel pumps
One on each engine. If these fail the engine will fail, there is no backup. More fuel than the engines require is sent to the pump in order to create motive flow.
Motive flow ejector pumps
- Operate using motive flow pressure
- Motive flow is created using the excess fuel sent to the engines by the high pressure engine driven fuel pumps
- As fuel flows through the restriction pressure decreases and sucks in more fuel
How many flow ejector pumps…
8 total
2 Transfer ejectors
4 Scavenge ejectors
2 Main ejectors
Fuel flow
Center tank -> Transfer ejectors -> Main tanks -> scavenge ejectors -> Collectors tanks -> main ejectors -> engine
Transfer ejectors
FSC will open the appropriate transfer valve when the main tank drops to 94% of its capacity
FSC will close transfer valve when tank is full
DC electric boost pumps
- 2 of them
- Allow for fuel to flow to the engine when the main ejectors aren’t working. Used during engine start.
What happens if both scavenge ejectors fail
Fuel can be gravity fed to the collector tank. No action is required.
Can the primary ejectors cross feed fuel
No. There’s a one way valve that prevents this from occurring.
Can you manually turn on the boost pump?
No, but you can arm them. The FSC then turns on the boost pump when low fuel pressure is detected from the main ejector on than side. When the FSC turns on one boost pump it always turns on the other boost pump as well.
Boost pump switchlight
- INOP illuminates any time the boost pump is not armed (not selected in, flush with the panel). Also illuminates when the boost pump fails
- ON illuminates when when the boost pump is on
Emergency fuel shutoff valve (SOV)
- Stops the fuel of fuel to the engine
- Controlled by the EIGINE FIRE PUSH switchlight.
Fuel heat exchanger
Cold bulk fuel is heated by the high temperature engine oil passing through the heat exchanger.
APU fuel pump
Draws fuel from the left collector tank
Internal bypass valve will allow suction to keep APU running if the pump fails. This Valve will not allow the APU to be started if the pump
APU shutoff valve
…
How many fuel quantity probes
17 total
6 in each tank
3 in the center tank
1 in each collector tank
Magnetic level indicators (MLI’s)
A float type measuring system on the bottom of the wing.
Emergency Procedures checklist (EPC’s)
PF: “Cancel, identify.”
PM: Press the caution/warning button and read the associated message
PF: If EPC, “reference the EPC for…”
PM: Runs the correct checklist and says, “EPC complete… refer to the ____ tab for expanded procedure.”
If QRH: “I have the radios and controls, reference the QRH for…”
