10697215
Description
Mind Map by Kenzie Evans, updated more than 1 year ago
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Created by Kenzie Evans
almost 7 years ago
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Fuel Feed System: Function
- Two methods of Pressure Controlled Fuel Feed
- High Pressure Pumps
- Also called override and jettison pumps
- Deliver twice as much pressure as standard boost pumps
- Forces discharge check valves on standard pumps to close
- Prevents fuel flow from standard pumps
- Prevents fuel flow from standard pumps
- Forces discharge check valves on standard pumps to close
- Also called override and jettison pumps
- Sequence Valves
- Installed at the pump outlets of standard boost pumps
- Reduce output pressure
- Allows some fuel back into the tank
- Allows some fuel back into the tank
- Reduce output pressure
- Installed at the pump outlets of standard boost pumps
- High Pressure Pumps
- Electrical Fuel Feed Management
- Performed automatically
- Controlled in accordance with flight phases
- Taxiing phase, centre tank feeds engines
- Other pumps on standby
- Other pumps on standby
- Take-off phase
- Occurs when flaps are extended for take-off
- Engines supplied individually
- Two boost pumps from each main tanks 2 and 3 (engines 2 and 3 respectively)
- Double capacity centre tank boost pumps for engines 1 and 4
- Two boost pumps from each main tanks 2 and 3 (engines 2 and 3 respectively)
- Occurs when flaps are extended for take-off
- Cruise phase
- After take-off when flaps have been retracted
- Centre tanks and stabilizer tank are emptied first
- Inner main tanks used next
- All engines now supplied by double capacity override and jettison pumps in main tanks 2 and 3
- After take-off when flaps have been retracted
- Performed automatically
- Fuel Scavange
- Reduces amount of non-usable fuel in the tanks
- Most commonly used method uses jet pumps
- Boost pumps supply jet pumps with pressure they need for operation
- Scavenged fuel is pumped to the main inner tank
- Another method uses electrically driven scavenge pump
- Controlled automatically as fuel level drops below certain threshold
- Pump fuel into a main tank
- Controlled automatically as fuel level drops below certain threshold
- Reduces amount of non-usable fuel in the tanks
- Fuel Recirculation
- Ensures proper cooling of engine oil and integrated drive generator oil
- Fuel from tank is pumped through engine oil cooler which
heats the fuel and cools the engine oil
- Fuel then passes through the high pressure gear driven
engine pump to the burners on the engine
- Some fuel is diverted and passes through a bypass valve
- Proceeds to the Integrated Drive Generator (IDG) cooler
- Fuel is heated further and then recirculated and mixed
with new fuel ready to repeat the process
- Fuel is heated further and then recirculated and mixed
with new fuel ready to repeat the process
- Proceeds to the Integrated Drive Generator (IDG) cooler
- Works well until engine runs at lower speed and there is a high electrical load on the IDG
- As engine runs slower, the cooling becomes critical as there may
not be enough fuel for cooling
- As engine runs slower, the cooling becomes critical as there may
not be enough fuel for cooling
- Solenoid activates on the fuel return valve
- Return valve opens and returns fuel to the tank
- Cool fuel is mixed to cool down the hot fuel
- Cool fuel is mixed to cool down the hot fuel
- Return valve opens and returns fuel to the tank
- Ensures proper cooling of engine oil and integrated drive generator oil
- Fuel Boost Pumps
- Generally impeller type
- Impeller forces fuel from the inlet to the pump outlet by centrifugal force
- Boost pump can be removed from canister without draining fuel
- Special removal valve shuts off the fuel inlet as the pump is pulled out
- Special removal valve shuts off the fuel inlet as the pump is pulled out
- Generally impeller type
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