A330 fuel imbalance

[BITE System]

Was recently having a conversation with a TRE on the A330/340 and he came out with a statement… if you lose an engine on the A330, you should open the cross-feed and leave it open (assuming you have established that you do not have a leak).
He was totally against following the ECAM and monitoring the fuel and when a fuel imbalance started to develop, then follow the fuel imbalance procedure which calls for the cross-feed to be opened and the pumps on the low side to be turned off (low side would be the side with the good engine) his point being that, you have a good engine with pumps on the other wing sending fuel to it! I personally like to stick to airbus procedures, but was interested in getting some other opinions……..

[bobrun]

Interesting.

I'm confused as to what exactly is wrong with having the pumps from the other side feeding the good engine? It only means the fuel has to go through a longer pipe to get to the engine, that's all. And there's three pumps on each side, with only one being enough to feed the engine. I don't really get what point he was trying to make (assuming there's no leak/damage, as you mentionned). :confused:

[Bullethead]

One potential problem with having the crossfeed valve open with both sets of wing tank pumps on is that if there is any difference in output pressure from one set of pumps then the fuel will feed from the tank with the higher pressure and cause you an imbalance anyhow and possibly run that tank dry while you are confidently motoring around believing that the fuel is feeding evenly from both tanks.

This imbalance will not occur in the sim as the fuel pumps are computer modelled to be identical. Real life isn’t like that.

Better to stick with the standard procedure.

Regards,
BH.

[PappyJ]

Sounds like another one of these TRE folks who believe that the three little initials give them god like knowledge and ability. TRI's and TRE's are supposed to be teaching (and testing) manufacturer's recommended procedures, not their unfounded opinions.

As an aside, that wing tank pump doesn't keep the engine running; the high pressure pumps do that. Tank pumps ensure that a VOLUME of fuel is available to feed those high pressure pumps. Where that volume of fuel comes from (on side or off-side tank) makes no difference what-so-ever to the engine pumps. In fact, gravity does the same thing (with limitations).

Bottom line, follow the recommended procedures and question everything a TRE (or anyone else) tells you which is NOT backed up by the manufactures approved documentation.

[jettison valve]

Not being a pilot myself, but I would suspect the flight crew to be extra vigilant as to where the fuel is during a one-engine out situation (I know you have other things to look at, too...:ok:).

Secondly, wasn´t there a "FUEL - wing tank imbalance" warning if the l/h and r/h inner tk fuel quantity differs by a certain quantitiy (3t?)?

Thirdly, I am very sure that the A330/A340 (classics at least) will give you a L/H (R/H) wing tk low level warning. Should leave enough time to reconfigure the fuel supply to the remaining engine.
(A3456 used to be different, see Virgin´s diversion into AMS a few years ago).

Finally a question to the operating crews: I seem to remember that in case of a crossfeed valve failed closed, the procedure said to push the outer-to-inner tk xfer p/b, and to "slip" the a/c with one wing down (thus initiating gravity xfer through the refuel gallery).
Has anyone done this in flight? What were the xfer rates??

Cheers, J.V.

[PappyJ]

seem to remember that in case of a cross-feed valve failed closed, the procedure said to push the outer-to-inner tk xfer p/b, and to "slip" the a/c with one wing down

You are correct. At least on the A330, the procedure is to maintain a 3 degree wing down on the lighter side, then module the imbalance through bank angle. Transfer rate? Don't know.

[BITE System]

Thanks for all the replies.

Bullet/Pap

I agree with your comments. I think Airbus would have gone through a lot of different situations in order to make sure that the fuel system works with an acceptable level of safety. Having held instructor ratings on Boeing aircraft, I always found that the manufacturer’s procedures are usually the most thoroughly thought out, I am not saying we should not question things but to start making up your own procedures is not always wise.

[rudderrudderrat]

Hi. Interesting posts here. Assuming no leak -

1) If the Fuel Crossfeed is left open, then even with a pump delivering a higher pressure, the imbalance will not develop any faster than having the crossfeed closed.

2) ECAM should direct you to turn fuel pumps on and off to maintain balance within limits.

3) All the fuel is now available all the time - even if one tank runs dry.

4) What does the A330 ECAM "Fuel L+R Wing Tk lo lvl" say to do with the Fuel X Feed? Please see my thread
http://www.pprune.org/tech-log/394555-a320-l-r-wing-tk-lo-lvl.html

I'm concerned that Airbus have hidden my fuel guages on a systems page and replaced them with a total FOB - but not provided me with a fool proof fuel management procedure when single engine.

[TyroPicard]

Airbus write a procedure that covers every fuel state from all tanks full to minimum landing fuel, and it is left to the crew to manage the fuel system safely. There may be trim tank fuel, or centre tank fuel if fitted. MONITOR FUEL IMBALANCE covers every situation.
The a/c location is also relevant - at FL 350 over Europe, if you land asap at an aiport 100 miles away, what will the fuel imbalance be if you leave the crossfeed shut? 1,000 kg?
But if you are EROPS the maximum allowable distance from an alternate, you will need to manage the fuel balance.

It is easy for a TRE to fall into the trap of thinking in terms of simulator training/testing only - which may have happened in this case...

[groundfloor]

Check out your AFM (Flight manual) from which the Airbus procedures are derived. Airbus do not differ from the AFM - so when the TRE or whomever decides to be different to Airbus/Boeing they normally end up being different to the Flight manual.

Be very interesting explaining that your position as a Company TRE..etc gives one the authority to overrule the certifying authority - in the airbus case the European Aviation Safety Agency.