Fuel System Flashcards
(47 cards)
Explain the fuel system.
Two separate wing fuel systems connected via a cross-feed line and valve.
Each wing consists of a main and an auxiliary system.
The main system holds 386 gallons, the auxiliary holds 158 gallons.
Main - 2,586 pounds
Auxiliary - 1,058 pounds
Total - 544 gallons, 3,644 pounds
How does fuel flow to the nacelle tank?
Gravity fed
How is fuel transferred from the auxiliary tank into the nacelle tank to the main fuel system?
Via a jet pump
Which fuel is used first? Auxiliary or main?
The auxiliary
How many types of fuel pumps are there? What are they?
Two - high pressure fuel pump & low pressure boost pump that are engine driven through the accessory drive section
What does the high pressure fuel pump do?
Delivers fuel to the engine
What does the engine driven boost pump do?
Delivers low pressure fuel into the high pressure fuel pump to prevent cavitation and ensure continuous flow of fuel
Cavitation - air bubbles generated inside of the pump because the partial pressure drop of the flowing liquid, resulting in a cavity at the relevant part. The changes in the pressure turn the liquid into vapor then back to liquid
If the engine driven boost pump fails, which pump should be actuated?
The electric standby boost pump
How is the low-pressure standby boost pump powered? Where is it submerged?
Electrically, the bottom of the nacelle tank
Explain the routing of the fuel from the tank to the engine.
Main tank through the firewall shutoff valve. Through the low pressure engine driven boost pump to the firewall fuel filter and pressure switch through a fuel heater to the engine fuel pump. Then onto the fuel control unit (FCU) and then through the fuel flow transmitter. Through the dual fuel manifold to the fuel sprayer nozzles and into the annular combustion chamber.
Fuel can also be pulled after the firewall fuel filter to supply the auxiliary tank transfer system with motive fuel flow.
While the auxiliary system is in use, how is fuel transferred from the aux tank to the nacelle tank?
Via jet transfer pump
When there is auxiliary fuel available, fuel is automatically transferred from the aux tank to the ______ tank.
Nacelle
What principle does the jet transfer pump in the auxiliary tank operate on?
The Venturi principle - using the fuel and boost pump for motive flow
How does the jet pump draw fuel from the aux tank?
The Venturi effect creates suction in the jet pump, which draws the fuel
How long is the time delay built into the automatic transfer system during engine start?
30-50 seconds
Why is there a time delay in the automatic transfer system during engine start?
To allow all the fuel pressure to be used for engine starting
What should be monitored early in the flight pertaining to the fuel system?
The auxiliary fuel level to ensure the transfer of fuel is taking place
What will extinguish the red FUEL PRESS warning light?
Fuel pressure supplied by either the engine driven boost pump or the electric standby boost pump (25-30PSI), a minimum of fuel 10+- 1 PSI is required to extinguish the light
What does the motive flow valve do?
Allows for fuel to flow through the auxiliary transfer line
What would extinguish the amber NO TRANSFER light on the fuel panel?
If the auxiliary fuel transfer line has at 4-6 PSI
When the auxiliary tank empties and the motive flow valve closes, why does it NOT illuminate the NO TRANSFER light?
Because there is no more fuel left to transfer
When would the NO TRANSFER light illuminate with fuel in the aux tanks?
If the motive flow valve closed or if motive flow pressure was lost in the transfer lines
If the motive flow fuel pressure was lost and the NO TRANSFER illuminated, what could you do to extinguish the light?
Manually energize the motive flow by placing the auxiliary transfer switch from AUTO to OVERRIDE, which would bypass the automatic feature in the aux transfer system and send DC power directly to the motive flow valve.
On SN BB-32 and subsequent models, OVERRIDE switch does not extinguish the light until the motive flow valve has opened.
On SN BB-2 thru BB-31, selecting to OVERRIDE will extinguish the light but doesn’t guarantee fuel flow. Monitor the aux fuel level to verify its decreasing.
What’s the purpose of the firewall shutoff valves?
Close off the fuel flow to the engines
