A320 Refuelling On Batteries Only
 

Sometimes we get the outboard tanks half empty after refuelling, and especially after refuelling on batteries only they can be found completely empty, with the inners containing the correct total quantity requested.

The system is for sure not designed to make this happen this way, but it happens...

This puzzles us a bit.

Although I've got my personal theory to explain this, I'd like to hear from experienced people on this subject.

Thank you,

I am no expert, but if you check FCOM 1.28.30 p1 you will see that
the transfer valves are not in any hot bus. All the other necessary elements are, but not the xfer valves.
I guess they are fail safe to open when not electrically supplied, so all the fuel entering to the outer tanks goes to the inner ones during a refueling on bat only.

What is your theory?

Quite often this happens because the aircraft is shut down after the transfer valaves have opened during the previous flight. The REFUELG switch on the fuel panel is what resets them, so if power is removed without a refuelling operation taking place, the valves will stay open. As microburst2002 suggests, the valves are not powered when battery refuelling. When refuelling with the valves open, the fuel goes into the outer tanks and straight into the inners, without filling up the outers first.

The reason you might see outer tanks half full in this situation is if you put AC power onto the aeroplane during the refuelling process, which shuts the valves and starts filling the outers. If there is less than 1500kg to refuel from this point, the refuelling operation will end before the outers are completely full.

That's exactly what I thought!

Strange that Airbus has not issued a bulletin or some sort of advice in their manuals...

Thanks gentlemen for your time.

Your theory is correct. Other people know about it as well. Why do Airbus need to do what you suggest?

I agree with TyroPicard.

There is no restriction or limitation whatsoever.
After start, outer tanks get full after a while, from fuel returning to tank anyway.

The 321 has no outer tank, so I don't think it is a big deal to go with less than 750 Kg in the outers in a 320 as long as you have enough fuel for the flight.
Unless it has a significant impact in center of gravity.

Anyway it is worth noting that in the cockpit checks we confirm that the fuel quantity is correct and the fuel is balanced, but I have never checked that the outer tank fuel is 750 kg.
I guess that if we find the outer tanks to have less or no fuel at all we can consider that as a double xfr valve failed open. By the way, according to the MEL we can dispatch with an (o) that is like nothing. No big deal, then.

The FCOM 1 gives little information, as usual. For instance, there is not much about the FLSCU. Which BUS supplies it, or them?

FCOM 1 lack of info
 

It would be great if airbus amended FCOM1 to provide more systems info and beef up FCOM 1

or the could add more systems stuff in general


We dont we start a movement to petition airbus to do this.?

I do not have the time to go to the maintenance control manual. Some of the mcm stuff needs translation for pilots

Well, I know that's no big deal, but a few words spent for letting people know what to expect on this rare occasion (refuelling on batteries only) would be nice...

I've read/been told that the A321 wings are structurally different from the other A320 family members and physically come from a separate manufacturing process (Can anyone confirm?). So would assume that limits from the A320 should not be applied to the A321 carte-blanc.

Guys,

What is the reason for mixing up things with A321. A321 wing has stronger structure, so no need for outer tanks.

Subject here is A320 which has outer tanks. It is no issue if the outers are empty after refuelling. No limitation mentioned. Fuel limitations concern imbalance, which is not our case. By MEL you can even dispatch with transfer valves failed (open).
Outers will become full after a while anyway if transfer valves are operating normally.

ICTV operatin
 

The ICTV's once open, will remain latched open until delatched, by a signal from the FQIC (either cockpit refuel or from the refuel panel). The latching logic is related to a number of relay's (Three per pair of ICTV). It is likely that from previous flight the ICTV will be open (say if landing with <1,400 kg (approx) in one wing) which occurs at approx 750 kg in one inner cell.

If then refuelled on battery, as gary & microburst have said, the ICTV actuators are not powered and although "delatched" will remain open until electrical power is put back on the aircraft. In this sense the FLSCU, once the low level sensors are wet (approx 750 kg), will enable the ICTV's to close. (the ICTV's are paired both front together and both rear together). The position of the ICTV's are controlled by the low level sensors (open when dry, close when wet and delatched).

Once ICTV's are closed the outer cell will fill up to it's max qty (approx 690 kg), from the IDG recirc as well as motive flow for the outer and surge tank scavenge jet pumps.

The reason behind dispatch with outers full is load alleviation -> fuel in the outer cell = less stress on the wing root area. Hence the MEL limit for ICTV's failed open and OPP failure. For this reason (and going off the subject) the A321 (as well as a slightly different system) has a stronger wing/fuselage join.

I can't remember clearly, but I think in the AMM procedure for refuel on battery there may be reference that if refuel on battery the outers may not be full & similarly a note somewhere in the FCOM at the refuel procedure part (unfortunately not having access to these docs I can't verify!):ugh:

I'm not sure what the MEL says but suspect there must be some kind fatigue limitation on take-offs with ICTVs open simply due to fatigue analysis. I doubt airbus have set up their lifetime fatigue rigs to account for ICTVs being open so from a fatigue pov, you're operating in uncharted territory.

I checked the maintenance manual, JetAGoblin, and what you stated is absolutely correct: "the transfer valves will close at the next refuelling" means that it is not the refuelling switch or similar that closes the valves, but the low level sensors, when they become wet again.

And I'd like to add something interesting: that is not true that there are absolutely no limitations to refuelling on batteries only: the AMM says that it won't be possible to get the maximum capacity.
In other words, when the high level sensors in the inners sense fuel, the refuelling stops.
But the inners are empty...

Here is a good reason for adding this point in the FCOM (there's nothing in the FCOM about it).

Cheers,
LEM

Say again please?

FLSCU
 

What he means is that, when the hi level sensors in the inner tanks become wet the refuel valves are shut. Normally when this occurs the xfr valves are closed and the outers are full, but in this case they are open an the outer tanks are empty, but the refuel valves close anyway.

I cannot see a case where this can pose a problem (a delay). Maybe that is why they don't mention it in the FCOM. If we need all the fuel, we can just wait until the airplane is energized to complete the fuelling. It will never be the cause of a delay.

Anyway it would be nice to have the info in the FCOM.

By the way, any expert can solve for me a mistery?

What is the electrical supply source for the FLSCU? Or it doesn't need it?
I have been looking at the AMM but I can't see it. I also don't understand that apparently it is a dual system, with FLSCU 1 and 2, and there are also channels, A and B. Probably it is not very important but I would like to know

Alternatively, if you wish the stab trim setting to be standard, then simply do a ground transfer of the fuel to refill the outers. Its in the FCOM and only takes a few minutes.

Microburst2002,

Now I see, LEM probably ment "But the outers are empty".
So you cannot fill the outers because wet inners high level sensors result in stopping the fueling. So your max amount will be aprox. 1400kg less. Should be a problem in very rare occasions I guess. Interesting to know though.

Meikleour,

I don' t think stab position difference is such a big issue in order to start ground fuel transfer process.

And as mentioned before, in the MEL, even failed open tranfer valves are dispatchable cat C (ten days) and the operational procedure only draws attention to the unusual fuel distribution.

Aristocles:
I never said that it was a big issue. In fact our laptop PC`s allow us to compute for a non-normal fuel distribution anyway if one so wishes I just posted to put the info out there for those who might want to learn. By the way, have you never emptied the outer tanks on the ground after a tanking sector when the conditions are conducive to upper wing frost and then ground tranferred to put warm fuel back into the outers to avoid having to de-ice?

No I haven't. But interesting to know how to avoid a de-icing in that case. Thanks.