5. Fuel System Flashcards
What tanks do the main and auxiliary fuel systems consist of and where are they located?
Main:
Integral outboard (wet wing), 4 rubber bladder tanks, and nacelle bladder. Fills at wingtip and flows downhill nacelle.
Aux:
One tank in wing centre section.
Where is fuel drawn from to deliver to engine?
Nacelle tanks
How does fuel transfer from outer wing to nacelle tank?
By gravity
What are the aux tanks constructed with?
Rubber bladder type
Why is there a 30-50 sec delay after start in automatic transfer system?
To allow all the fuel pressure to be used for engine starting.
Pilot should monitor that NO TRANSFER light is extinguished after this time.
How does the auxiliary transfer system stop when the aux tank is empty?
Will NO TRANSFER illuminate?
A float switch in the aux tank transmits a signal to close the motive flow valve. Normally 30-60 sec time delay to prevent cycling of the motive flow valve due to sloshing fuel.
NO TRANSFER will not illuminate as there is no fuel left to transfer
By what means is fuel transferred from the aux tank to the nacelle tank?
The engine driven or standby boost pump routes fuel through the normally closed motive flow valve, the jet pump and into the nacelle tank. Fuel moving through the jet pump Venturi creates suction.
What are the 3 functions of the standby boost pump?
- Backup for engine driven fuel pump.
- Pump AVGAS when flying above 20000ft.
- Pump fuel during crossfeed operation.
What prevents reverse flow from nacelle to outboard tanks when aux transfer system is in use?
A swing check valve in the gravity feed line
What happens if the motive flow valve/its circuitry fails in the aux transfer system?
Amber NO TRANSFER will illuminate. Valve can be manually energised by placing the AUXILIARY TRANSFER switch from AUTO to OVERRIDE.
Where are the firewall shutoff valves powered from?
No. 3 (left) and No. 4 (right) dual fed buses. Also from hot battery bus, so they can be operated regardless of battery switch position.
When they are closed fuel is cut off from engine
What is the primary function of the engine driven boost pump?
To deliver low pressure fuel to the engine high pressure fuel pump, thus preventing cavitation
What is the operating capacity of the engine driven boost pump?
1250pph at a pressure of 25 to 30psi
What pressure decrease will trigger a FUEL PRESS light?
If fuel pressure drops below 10 +/-1 psi
If a standby boost pump fails, can cross feed be accomplished?
Only from the side of the operative standby pump