Fuel Balancing 744

[Obscurum per obscurius]

Anyone have any thoughts vv Fuel Balancing on the 744. Do you do it prior to the message or don't touch till she tells you to?

[Intruder]

Our FHB has no procedures for balancing unless the light comes on. OTOH, many pilots will balance when the "Fuel Tank to Engine" annunciation is made. It's not necessary, but makes some people feel better.

Just make sure you keep enough pumps running and the correct crossfeeds running while you do it, and confirm proper final configuration before turning off the fuel synoptic!

[Feather #3]

It isn't necessary right up to the point where you get a "FUEL QTY LOW" message and caution in the terminal area, distracting you from a busy approach!

"Tank to Engine" is a good time to balance to save the above. Those who worry about undetected fuel leaks are not using their "how-goes-it" charts correctly. But maybe that's only if you fly A330's?

G'day

[Right Way Up]

There should not be a significant imbalance unless you have a problem, and in that case you will have an eicas message. Am a bit peeved at guys balancing with 400 kgs imbalance (insignificant!) waiting until balanced and then resetting fuel tank eng switches. By then imbalance 200-300kgs other way.

[darrick]

Is this an issue in regards to CG for ultra-long flights on the 744,s and the A340,s and what is the correct sequence with regards to utilizing reserve tanks? tanks in the horizontal stabilizers etc

possible interview question

thanks

[BlueEagle]

The fuel in the horizontal stabiliser is amongst the first to go! Failure to do so will lead to serious C of G problems.

[darrick]

Thanks BlueEagle
Darrick

[*Lancer*]

darrick,

Fuel Balancing is a symmetrical problem so isn't going to affect longitudinal CofG...

Body fuel is the first to go - always from the Centre Wing Tank, with the Stab transferring first, then the Aux tank if fitted. Then the inboard wing tanks (and reserves) until all wing tanks are equal. Then all wing tanks together (Tank to Engine).

If the Stab tank doesn't transfer you probably have just over 3 hours before you MUST be on the ground.

Lancer

[BlueEagle]

Just to clarify my previous post, on the B747-400 the Stab tank will start to transfer when the Centre tank is down to about 36,470kgs of fuel. As Lancer says, the CWT is the first to feed , if the Stab tank doesn't transfer then you will need to find somewhere to land before an out of trim situation develops.
To say it will be burnt by TOC isn't very helpful so I have edited that bit out, that is what frequently happens but is a factor the total fuel load rather than how the system operates.

[XTRAHOLD]

You balance only if the EICAS message comes on, otherwise you don't. The only real interesting situation regarding fuel balancing arises when your tank quantities become unreliable. This happened to me some time ago when I had 6 tanks with densitometer failures driving the fuel management card crazy. On that situation, we used the calculated fuel figure and made up our own fuel used chart (F/F x time) to figure out how much we had left in all the different tanks. When the fuel imbalance message came up, we relied on the ACMS flight control display on the lower display to make sure the balancing was really working. Kept us realy awake on the 14 hour sector!

[darrick]

Thankyou gentlemen,

I came accross a Cathay Pacific intro video for the 747-400.
with your inputs, I can better appreciate the significance of the fuel balancing explanations on the tape and touched on in Handling the big jets.

BlueEagle, Lancer and Xtrahold

Thanks again
Darrick