View Full Version : fuel imbalance

16th Aug 2001, 08:48
How much tolerance is there in the W&B for a fuel imbalance in a 767, or any other jet for that matter ?

Say you had full left tanks, empty centre and right.

Would the plane be unflyable ? Could you takeoff ? ... land ??


Capt Claret
16th Aug 2001, 11:28

Can't answer re B767, but on the Brits revenge, the BAe146, in standard fit, there are 3 fuel tanks. One in each wing and a centre tank, basically in the fuselage roof.

The capacities in round figures are: 3650 kg per wing and 2000 kg in the centre tank.

The AFM limits fuel asymmetry between wings to a maximum of 680 kg (1500 imperial lb). There is no reason given that I am aware of, and assume the reason could vary between aileron/roll spoiler ability to keep wings level (which I doubt), to bending moments at the wing root, to something else I've never considered.

18th Aug 2001, 14:46
On the A320 max imbalance between wing tanks before ECAM warning is 1500kg......500kg imbalance for take off.....

On the B737, the Boeing Ops manual states...

max qty wings 4827kg each
max qty centre 7448kg
max lateral between wings 453kg taxi take off flight or landing.

Both main tanks must be full, if centre tank contains more than 453kg, presumably limited by MZFW

Hope that helps

Tailwinds ;)

18th Aug 2001, 15:37
In the Citation II, each wing can contain 2,500 pounds of fuel. The max imbalance between them is 600 pounds.


18th Aug 2001, 21:59
Ok, lotsa numbers being thrown around here.

Have any of you done a sim test with a radical fuel imbalance ?

What would the effect be on the plane ?


18th Aug 2001, 23:21
Doing it in the sim may not be a valid test of handling.

Unless the sim is programmed to replicate the condition you want to test then any behaviour observed is, at best, an extrapolation from already programmed behaviour.

19th Aug 2001, 04:17
Don't try this at home.
The manufacturers specs for the Fairchild F-227 specify a maximum fuel imbalance of 500 lbs. A friend hit a flock of snow geese one night on approach to KSYR. The left prop threw one through the top of the left outboard fuel tank, and he lost all the contents, like pronto. They landed with about a 1500 lb. imbalance - i.e. 1000 lb. over max allowable. They needed full aileron and some asymmetric thrust to maintain control, but the airplane flew.

Lord Lucan
19th Aug 2001, 13:18
I would have thought that if he had lost one prop, he would have been using quite a bit of asymmetric thrust! ;)

[ 19 August 2001: Message edited by: Lord Lucan ]

23rd Aug 2001, 01:33
454kgs max imbalance on a 737

23rd Aug 2001, 06:00
From a technician's point of view, fuel balance is very important in some aircraft due to structural limitations and where the CG is. I have seen a Merlin with one wing being defueled for maintenance and the other wing 85% full lean towards the full tank. The line department then moved the plane by tug and the light side gear came off the ground and caused the full wingtip to be damaged. Very ugly!!

23rd Aug 2001, 23:15
Dont' remember the details, but a number of years ago, an Eastern 727 developed a signifigant leak in one wing. As I recall, they had to dump fuel to keep it flying, and landed ASAP. They had full control deflections and just barely made it. I think it was about a 8000 lbs. imbalance.

24th Aug 2001, 01:32
Some years back, for reasons I won't get into, I was flying a 767 and the fuel got 12,000 lb. out of balance. By the time we landed, we were still 10,000 pounds out. The ailerons were noticeably off center, but I was amazed that there were really no significant control problems. I think the usual limit of 1500 lb. or so is set just so they don't have to go to the trouble to flight test greater numbers.

26th Aug 2001, 09:36
An SV TriStar departed JED in the early 80's with a 24,000 kg imbalance, good thing the captain was an old C-46 pilot and kept it in the air. The refueller went to jail as I recall.

26th Aug 2001, 10:35
"The refueller went to jail." What happened to the flight engineer?? :confused:

26th Aug 2001, 11:27
The F/E was suspended for investigation and then sent for a short retraining. Seems the refueler forged the numbers on the uplift sheet and it did not help that the #3 tank gauge was inop.
The F/O complained to the fleet manager that the Captain did not keep him in the loop just after liftoff. The Captain later commented that at 200 feet AGL with his hands full he did NOT consider it the proper time to hold ground school.

31st Aug 2001, 22:43
For the 747-200 there are no specified imbalance limits, so, some time ago, a group of flight engineers from my company wrote a letter to Boeing regarding the subject. Boeing reply: "Fuel balance shall always be maintained. But if you have any other questions, please donīt hesitate ..."

Just in case you were thinking of asking your manufacturer... :p