Fuel balancing of B747-400
Guest
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Fuel balancing of B747-400
Good morning! gentlemen..
I'm a newcomer of B747-400.
My B747-400 Operating manual says "To maintain CG and reduce drag ,operate the airplane whithin limits of FUEL IMBALANCE EICAS advisories."
Q1> For lateral balance, we may balance 1&4 or 2&3 tanks.But some old pilots always hesitate to turn off the main pumps of the lower fuel tanks. I want to know the ways you are doing for lateral balance.
Q2>For longitudinal balance , pilot may open all X-feed valves and turn off the fuel pumps in the lower tanks.
Does this mean we have to maintain the fuel quantity of inner tanks lower than the outer?( some pilos always open lower EICAS for that. They say they can reduce the wing load and save the fuel with that.)
Q3> Do we have to wait util the EICAS message comes on for fuel balancing or
do you have any personal limitations for fuel balancing?
Q4>How much fuel can we save with the fuel balancing?
Any informations will be very helpful.
Thanks...
I'm a newcomer of B747-400.
My B747-400 Operating manual says "To maintain CG and reduce drag ,operate the airplane whithin limits of FUEL IMBALANCE EICAS advisories."
Q1> For lateral balance, we may balance 1&4 or 2&3 tanks.But some old pilots always hesitate to turn off the main pumps of the lower fuel tanks. I want to know the ways you are doing for lateral balance.
Q2>For longitudinal balance , pilot may open all X-feed valves and turn off the fuel pumps in the lower tanks.
Does this mean we have to maintain the fuel quantity of inner tanks lower than the outer?( some pilos always open lower EICAS for that. They say they can reduce the wing load and save the fuel with that.)
Q3> Do we have to wait util the EICAS message comes on for fuel balancing or
do you have any personal limitations for fuel balancing?
Q4>How much fuel can we save with the fuel balancing?
Any informations will be very helpful.
Thanks...
Guest
Posts: n/a
WP5944
Fuel imbalance should not normally cause problems and the quantities which cause the EICAS messages have, obviously, been test flown to establish that there are no handling problems. Really the only problem arises from the CAUSE of the imbalance. If its due to a fuel leak, then the QRH will assist. As far as pump deselection is concerned, as long as the appropriate X-feed selections have been made first, again there should be no problems. Bear in mind that the backing pumps will be assisting gravity in feeding fuel so fuel starvation should not be a concern.
Q2. NO. The fuel system is very well designed and will alert you to the necessary configuration changes. Don't try to 'second guess' the system - it takes care of the wing loads quite nicely on its own if you follow the book. The only time one would expect to see the inners significantly lower than the outers would be during the last stages of fuel jettison - below about 52 tonnes total.
Q3 Wait for the message - that's how the system was designed to work.
Q4 No idea, but I somehow doubt that the results would justify the effort.
Merry Xmas!!
Fuel imbalance should not normally cause problems and the quantities which cause the EICAS messages have, obviously, been test flown to establish that there are no handling problems. Really the only problem arises from the CAUSE of the imbalance. If its due to a fuel leak, then the QRH will assist. As far as pump deselection is concerned, as long as the appropriate X-feed selections have been made first, again there should be no problems. Bear in mind that the backing pumps will be assisting gravity in feeding fuel so fuel starvation should not be a concern.
Q2. NO. The fuel system is very well designed and will alert you to the necessary configuration changes. Don't try to 'second guess' the system - it takes care of the wing loads quite nicely on its own if you follow the book. The only time one would expect to see the inners significantly lower than the outers would be during the last stages of fuel jettison - below about 52 tonnes total.
Q3 Wait for the message - that's how the system was designed to work.
Q4 No idea, but I somehow doubt that the results would justify the effort.
Merry Xmas!!
