FUEL SYSTEM EXAM REVISION Flashcards
(40 cards)
What are the main tanks?
What are the type?
Numbers 1,2,3,4
- Integral type (tank boundary formed by the sealed structure of outer wing box beam)
What are the aux tanks made up of?
Baffles?
Three rubber cells contained within sealed compartments created by the wing structure. The ribs act as baffles between the individual cells
How is leakage dealt with in the aux tanks?
Any leakage of fluid or fumes into cavity between the cells is drained or vented overboard
How are the external tanks constructed? (2)
- Welded aluminium sheet
- Divided into three compartments by bulkheads/baffles bolted to the ends of the center section
Condensate drain location & purpose (3)?
- Mounted in various low points in the tanks
- Remove accumulated water, drain tanks of any unusable fuel, and give a second chance of stopping leaks if primary seal fails
Main tank boost pumps; location & how are they cooled (2)
- In surge box of each main tank
- Fuel cooled & lubricated
- Secondary cooling vanes for when pump operates in low level fuel
General function of the surge box & location
- House the boost pumps, ensures they always remain submerged in fuel. check valves allow fuel in but not out
- Located in the lowest point of the main & external tanks (nil in aux tanks)
Vent system purpose (2)
Vents each fuel tank to atmosphere to avoid pressure build up during refuelling or negative pressure developing during fuel burn.
What vent system is used in the aux tanks/No 2/No 3 tanks?
What does it consist of?
- The wrap around system
- Two open ended tubes starting at opposite ends, running around & terminating at the vent tank = one end always free to vent
What vent system do the No 1 and 4 tanks use?
What does it consist of?
- Vent valve
- Tubes run span wise from vent tank to each end of the fuel tank
- Each end is fitted with float valve that closes when fuel reaches them
- In theory only one should be closed at a time
External tank vent system
the anti-syphon system; doesn’t use vent tank but connects top area of tank to atmosphere through anti-syphon loop
If the main tanks are venting fuel, where does it come out?
Main
Aux
Main tanks; out of two vents L/R between wingtip and outboard engine
aux; aft of main landing gear
Main tank boost pumps; location & how are they cooled (2)
- In surge box of each main tank
- Fuel cooled & lubricated
- Secondary cooling vanes for when pump operates in low level fuel
Main tank boost pumps; properties (4)
- 3 phase
- 115V
- 400 Hz
- Brushless centrifugal type
Main tank boost pumps; output
- 24 PSI (no flow)
- 15 PSI at 6000 lbs/hr
Main tank boost pumps; when does the thermal protection circuit shut off the pump?
temp inside motor housing > 375deg F
Main tank boost pumps; what is installed should the pump fail?
- bypass facility which allows the engine to gravity (suction) feed
Main tank dump pumps; properties & output
- Same properties as main tank boost pumps
- 40 PSI (no flow)
- 28 PSI at 6000 lbs/hr
What is the rule for aux and external boost pumps wrt the main boost pumps, why?
The aux and external boost pumps will override the main tank boost pumps whilst pumping fuel into the fuel manifold when selected on.
This is due to the output being higher
Fuel pump power supplies;
What does the LH AC Bus power?
- No 1 tank boost
- LH Ext fwd
Fuel pump power supplies;
What does the ESS AC Bus power?
- No 2 tank boost
Fuel pump power supplies;
What does the MAIN AC Bus power?
- No 3 tank boost
- All main dump
- both aux
- Both ext aft
Fuel pump power supplies;
What does the RH AC Bus power?
- No 4 tank boost
- RH Ext fwd
Where is the water removal system located?
What are its functions?
Main tanks ONLY
- Removes water from low points in tanks
- Increases maximum usable fuel capacity
- Provides positive supply of fuel to surge tanks irrespective of a/c attitude
- Removes fuel from vent system tanks
