A320 Strange fuel consumption scenario!

[hossein]

Hi there, please check my hyperlink in below, and answer my questions if you can. This is happened few days ago in my flight, and all photos are taken at there real time.

https://onedrive.live.com/redir?resid=95F9F9B64CBFD873!3528&authkey=!ADtCQjMEABifZ2I&ithint=file%2cpdf

[sonicbum]

Hi hossein, I have read your document and your questions. Before starting to answer your questions I actually have one for you : what about applying the manufacturer's instructions when flying in normal / abnormal conditions ?

[Goldenrivett]

Hi hossein,

1. Is this happened because of any sensors or FQI fault?
Ans = No.

2. If so, is there any relation between these faults with HIGH EGT and HIGH OIL PRESSURE?
Ans = No.

3. How do FOB,F.USED and F/F showed such a these things? And which one is the most trustable reference?
Ans = They all seem reasonably reliable and sensible. (How much APU fuel was used?)

4. And if so, why we've had heavy left wing?
Ans = When you had the fuel X feed open, the fuel will be delivered from the tank with the pump giving the highest fuel delivery pressure (in your case the right tank pump).

5. If this flight had more than 1 hour duration, what should we expect more?
Ans = The right pump would continue to deliver all the fuel to both engines until you did the fuel imbalance procedure, which would involve turning the lighter (RHS) pumps off.

6. Is refilling a quiet amount of center tank for short flights being necessary?
Ans = No. I often see about 50 kgs fuel remaining in centre tank.

[sonicbum]

Applying the ECAM/QRH/FCOM procedures wouldn't be a bad idea too.

[NigelOnDraft]

Oh dear :sad:

I can only echo above posts. If you do not understand how your aircraft works, please at least follow the instruction book :{

[hossein]

Tnx for your quick reply dears,
Ofcourse we did all ECAM/QRH/FCOM PROC, even we're completely ready for worst case such as both engine flame out and all procedures through.
Maybe I didn't hit the point.
APU was INOP from start.
QRH FUEL IMBALANCE was done as you see in the picture.
The major question is why Left Wing Tank Quantity at detination is the same as we start from departure point. 3300 kg remains all the way on the left tank, no change, with consumption of Eng#1 ! Heavy left wing. Is it both left wing pump fault or what?

[tom775257]

QRH fuel imbalance requires both pumps to be turned off on the lighter side, you still have one on.

[C_Star]

QRH/ECAM etc. aside, with the pump setup as presented by Hossein I'd still expect fuel to be drawn from the LH tank...

What am I missing? Would there be any reason the remaining pump on the RH side had higher output pressure than the LH wing pumps?

As a side note, I've seen this happen to a CTR pump once. With Center tank in use we noticed a developing unbalance and eventually traced it down to LH CTR pump having lower output pressure than the corresponding wing pumps. There was no 'LO PR' fault, but the center fuel obviously didn't feed the LH engine.

Applying the "fuel auto feed fault" ECAM procedure didn't solve the issue. We eventually switched off the faulty pump and opened x-feed to enable the other CTR pump feed both sides...*

*After careful checking for possible leak

[Goldenrivett]

Hi hossein,
The major question is why Left Wing Tank Quantity at detination is the same as we start from departure point. 3300 kg remains all the way on the left tank, no change, with consumption of Eng#1

If "Total fuel on board 7600 kg
(3300kg each wing tank with NO IMBALANCE)"
Then you must have started with 1,000 kgs in centre tank, which was used once the Flaps/Slats were set to zero. Therefore you only used fuel from the Left Tank during Take off and early Climb (say 500 kgs).
You had at one stage 3440 Kgs in Left Tank (2730+710) which shows that the NRV (Non Return Valve) to the Left Tank was leaking slightly and that the pump output from the RHS pump was greater than the pump pressure of either of the two LHS pumps.

That is why all fuel plumbings have X feed valves etc. to prevent fuel migration from one side to the other. If you had turned both pumps off in the RHS, then only the fuel from the LHS would have been used.

[OSCAR YANKEE]

Hossein.

You file an ASR, and make a tech log entry

If the engineers cant find anything, you/they ask for the FDR to be removed, downloaded, and sent to Airbus for analysis.

Then, you will get your answers.

[NigelOnDraft]

What am I missing? Would there be any reason the remaining pump on the RH side had higher output pressure than the LH wing pumps?When you build a pump, it will have a specified nominal output pressure, and an acceptable "range". If you fit 4 of these identical pumps to an aircraft, by definition, they will all have slightly different output pressures.

As above, the QRH balancing process is clear - you turn off BOTH pumps on the lighter side. You then MONITOR very closely the balance, and do not let it build up. If you just turn off 1 pump, you might as well toss a coin in the air as to which tank will supply the fuel: L, R, or both.

[Sailvi767]

With a confirmed engine problem on climb out why did you not return to the departure airport? You also need to turn both pumps off to balance fuel.

[C_Star]

Thanks NoD. So in this case the pump feeding both engines is whichever has the highest output pressure...

How about balaning fuel in case of engine failure? In my outfit we are taught to switch the x-feed on and keep all 4 pumps in to draw fuel from both tanks to the live engine. In the sim it works like a charm. How about real life? I suspect it may lead to situation similar to that described by the OP?

[Denti]

It only works that way in the simulator because the pumps are simulated by a piece of software which of course has all of them running exactly on spec which in turn means the same output pressure for each pump. As explained above that never works in real life as there is an acceptable range of output pressure. Simply keeping all pumps on and opening the crossfeed valve is therefore pretty stupid as the result will be kinda random, not controlled.

There were a few pilots who used the same "technique" in the simulator in my outfit. They were reminded about the error of their ways and in some stubborn cases failed and send back for retraining (a failed check will only lead to retraining and recheck, nothing more no matter how long it takes).

Follow the OEM guideline on that and everything will be fine.

[tom775257]

Great question C* - We are taught exactly the same as you. Denti - where is this OEM information please re: eng fail case. Not doubting it at all, just wanting to read it!

[flyingchanges]

Best pump wins...

[Goldenrivett]

Hi C_Star,
How about balaning fuel in case of engine failure? In my outfit we are taught to switch the x-feed on and keep all 4 pumps in to draw fuel from both tanks to the live engine. In the sim it works like a charm.
If you have an engine failure, and keep the fuel X feed closed, the fuel imbalance will still grow at the rate you are consuming fuel by your running engine.

If you open the fuel X feed (with no fuel leak), then the imbalance rate cannot be any worse (it may even be less if you have a stronger pump on the dead engine side). The benefit is all the fuel is now available to your only running engine. You won't starve the engine until all the fuel is exhausted.

[C_Star]

Thanks Goldenrivett :ok:

Now it's perfectly clear - leaving x-feed on may not prevent imbalance, but won't hurt either and can prevent fuel starvation due to fuel mismanagement...

[Right Way Up]

Simply keeping all pumps on and opening the crossfeed valve is therefore pretty stupid as the result will be kinda random, not controlled.

There were a few pilots who used the same "technique" in the simulator in my outfit. They were reminded about the error of their ways and in some stubborn cases failed and send back for retraining (a failed check will only lead to retraining and recheck, nothing more no matter how long it takes).

Not as stupid as flaming out with fuel available because your company refuses you to fly an approach with the crossfeed open with all pumps running.

[Goldenrivett]

Hi Denti,
There were a few pilots who used the same "technique" in the simulator in my outfit. They were reminded about the error of their ways and in some stubborn cases failed and send back for retraining (a failed check will only lead to retraining and recheck, nothing more no matter how long it takes).

Did you really fail some pilots for ensuring they didn't run out of fuel?

Follow the OEM guideline on that and everything will be fine.
Which OEM guidelines are you referring to?

Look at fuel management QRH guidelines "Fuel Leak" ... Leak from engine/pylon confirmed."
After the engine is secured with:
TL ... IDLE
ENG Master (of affected engine)...OFF,
the next line advises:
"FUEL X FEED ... use as required,
If the leak stops, the crossed valve can be opened to rebalance fuel quantity, or to enable use of fuel from both wings."

After an engine is secured and no fuel leak confirmed, why can't you use the fuel from both wings simultaneously in your outfit?

[Ollie Onion]

Um, why did you apply the fuel imbalance procedure anyway? Surely you would just secure the engine at idle and then see how the fuel burn pans out, if it looks like it is going to be a problem THEN apply the feed procedure. In any case it would appear that you have just applied the fuel imbalance procedure incorrectly, you have only turned off ONE of the wing pumps which could result in fuel from the right tank being feed to the 'bad' engine if the pressure from the one wing pump still working is superior to the wing tank pumps in the left wing. Seems to me that you ended up running the no2 and no1 engine from the right tank and ended up with the reverse imbalance to what was expected because you didn't apply the procedure correctly. Usually in the sim with a full blown engine failure I will only consider the imbalance procedure if I have a Go around or an extended diversion and will only then apply it once I see an imbalance starting to form.

[NigelOnDraft]

How about balaning fuel in case of engine failure? In my outfit we are taught to switch the x-feed on and keep all 4 pumps in to draw fuel from both tanks to the live engine. In the sim it works like a charm. How about real life? I suspect it may lead to situation similar to that described by the OP? As Denti says and you suspect, works well in the Sim. In real life who knows, but likely as per OP :{

If you open the fuel X feed (with no fuel leak), then the imbalance rate cannot be any worse (it may even be less if you have a stronger pump on the dead engine side). The benefit is all the fuel is now available to your only running engine. You won't starve the engine until all the fuel is exhaustedYes... but as experience has shown, X-Feed is dangerous. Unless you really know the engine failure cannot have damaged the fuel system it is, IMHO risky.

Our training altered, if only in part because the ECAM drill also altered - the "Open X-Feed" IIRC was removed in a later software standard, and replaced with "Monitor Fuel Balance" or similar? I now tend:
Engine failure on takeoff
In ECAM drill write down the tank quantities, but don't touch anyhting unless urgent. Quick assessment v serious leak?
Complete climb, assessment, doodar etc.
Now look at fuel again - you will have built up a fair imbalance. Can now take a longer look at leaks and quantity/balance v "plan"
Now decide if it's worth balancing? If so do it, but keep an eye at every "review".
In the unlikely (or very likely in the Sim) event of a GA, reassess.
Summary: Fuel X-Feed and balance can spoil your day (Azores A330) and need to be treated with care = to me, 2 crew involved at low workload points.

Never mind what really happens, but if I was a Sim Instructor and saw someone merrily open the X-Feed I know I would now be pressing the Fuel Leak option :eek:

[Denti]

There is a specific fuel imbalance procedure that is run in case any fuel balancing is needed. Just opening all pumps and hope for the best might lead to some rude awakening. It has happened in the past and probably will again if used like that, and of course stuff like the OP experienced is a direct result of that.

And yes, opening the xfeed outside the scope of a procedure is very actively discouraged. By the way, both on the bus and the boeing in my outfit, for the same reasons. Just the limits are much tighter on the boeing with 453kgs imbalance instead of 1500kg on the bus.

As NoD said current software on the bus only uses the line "Monitor imbalance" which does not mean to push the xfeed button (although that still removes that line), instead our FCOM advises us to actively monitor the fuel situation for both leakage and imbalance. Writing fuel quantities down and comparing them later to fuel burn is a very good method of doing that. After all we have that nice table for our pen and paper...

[vilas]

NigelOnDraft
As you have said the procedure to simply open cross feed was changed because in real life it may not balance the fuel due to pressure difference in fuel pumps. So they changed it to "imbalance monitor" and if you see the fuel imbalance procedure in the FCOM at bottom it says:
Note: There is no requirement to correct an imbalance, until the ECAM fuel advisory is displayed.
So you do not have to do any thing at EFATO. When the advisory appears apply the procedure. That is how it is taught now. Incidentally airbus can be landed with one tank empty and the other full.

[safelife]

It sure can be landed, mind you you might just miss the required thrust to make it a good landing, with the feeding tank empty and the crossfeed off :O

[Goldenrivett]

vilas
There is no requirement to correct an imbalance, until the ECAM fuel advisory is displayed.
Correct. With all engines operating normally, then fuel used should be almost symmetrical and the ECAM advisory limit is there to reduce pilot work load.

So you do not have to do any thing at EFATO. When the advisory appears apply the procedure. That is how it is taught now.
When you have an engine failure, the fuel used will be asymmetric and you should anticipate that there may be a requirement to balance fuel. There are two types of pilots who:
1) Do nothing until ECAM says do something (which may be during a high work load situation)
2) Anticipate the problem and during suitable low work load opportunity, check there is no leak and then take steps to mitigate the potential fuel imbalance.

Which sort of pilots do you train?

Lessons Learned (http://lessonslearned.faa.gov/ll_main.cfm?TabID=4&LLID=73&LLTypeID=9)

[NigelOnDraft]

As Goldenrivett says, you can either start balancing the fuel on the SE Go Around with some real work / decisions to be done, or you could "plan ahead" in a low work load moment and maybe prevent the "Fuel Balance" ECAM ever occurring.

I know what I do, and would take any trainer to task who advocated the line of "you must not balance until the ECAM comes up" ;)

[vilas]

Goldenrivett
Just don't jump the gun.This is airbus procedure for EFATO and not my creation. I am talking about EFTO. During EFATO while applying ECAM there is no possibility of imbalance when every thing was balanced few minutes ago. So complete your other procedures, take your decisions. If you are landing in 30 minutes all that you say is not going to happen and as it is imbalance during landing is not life and death situation in airbus. Also fuel does not get balanced instantly you need time for that. But if your OEI flying time is going to be considerable then your need for that fuel itself is greater than any requirement of balancing and should make you apply the necessary procedure.

[Goldenrivett]

villas,
What gun?
If you are landing in 30 minutes all that you say is not going to happen and as it is imbalance during landing is not life and death situation in airbus.

You are missing the point about potential fuel starvation and intelligent fuel management.
Assume Fuel Loaded = 4,400 kgs i.e. 2,200 each side; and assume No 1 EFTO & 30 mins flying before ready to commence approach. Assume 1400 kgs was consumed (Therefore No ECAM warning yet)
Fuel distribution would be 800 LHS; 2200 RHS
Fly approach & GA and consume say 700 kgs before aircraft clean and MCT set.
Fuel distribution = 100 LHS; 2200 RHS.

Who would you rather have if you were a passenger, pilot A (who might do ECAM during the approach & GA when work load is high) or pilot B?

[vilas]

Don't make it so dramatic. Passengers don't know who is in front and how was he trained. My point is it is not necessary to check when ECAM says monitor imbalance. Once you have finished all actions and take a situational awareness decision fuel situation will be considered and if the fuel situation is like you stated you should apply the procedure. It depends on circumstances. There is no requirement means do not have to balance for balance sake, but if it is necessary because of the fuel scenario then apply it by all means. Even if you don't outer tank fuel transferred should trigger you to do it anyway in any situation.

[CONF iture]

Hi there, please check my hyperlink in below, and answer my questions if you can.
I would say that the higher EGT is probably due to an engine with more hours on it, and the higher oil pressure to one additional GAL of oil on that ENG 1.
For the fuel situation, as other have already stated, the R FUEL PUMP was stronger to the point to feed both engines but also to crossfeed to the left side at the same time.

[Capt Quentin McHale]

Hi hossein,


Looking at the data that you supplied I think you have two unrelated problems. Your fuel and engine instruments are ok, they are doing their job.


Engine first... 300kg fuel used difference due to left engine at flt idle and right engine at high power setting for some time. Look at your photos and compare EPR's and fuel flows.


Higher EGT suggests possible older engine with more wear and tear and therefore operates slightly harder to maintain selected thrust settings. All other parameters are stable.


Higher oil pressure with stable oil quantity and temp would indicate to me an impending oil filter blockage.


Now fuel... I can only assume you had 1000kgs of fuel in the centre tank at takeoff and used that first. Centre tank fuel pumps have a higher output pressure than the wing tank pumps. Looks to me like the left tank pumps may have a failed check valve either in one (rare) or both (extremely rare) pumps. This will enable fuel to pumped past the check valve and into the tank which results in that tank "making" fuel as indicated on your fuel page. This scenario will cause a run around circuit of fuel even with centre tank pumps off and wing pumps on. You will not see the left tank decrease until crossfeed valve is closed and wing tanks are supplying their respective engines. Hope this helps.

[clark y]

I've seen this occur a few years back with a wing tank pump fault. From memory the ECAM called for the faulty pump to be turned off and cross feed opened. This resulted in the same situation as hossein. At top of climb we had a 500 kg imbalance with the heavier wing being on the side with 2 good pumps. Never did find out the actual reason. I have always thought it could possibly be due to system plumbing ( pipe diameters, junctions etc) causing a Venturi effect and sucking the fuel from the side with only one pump operating to the other. Part of the reason for this thought is the inconsistency with the fuel temperatures. In hossein's case the left outer is a lot warmer which (if both IDGs are running well) would indicate that more fuel is returning from the engine. The right outer temp is probably colder because lower fuel pressure within the engine and minimal fuel returning to tank.
Please note this is all assumptions but the best I could come up with. I also don't think you could test this in a sim I think you would have to check it in a real aircraft.
Any engineers out there have any answers?

[Uplinker]

Have to say, I am disturbed that here we have a crew who are inventing their own fuel procedures; (leaving one pump on in the lighter tank) - why did you do that and not what it says in the QRH ???

Inventing your own drills is a highly dangerous road to go down guys.

Follow the QRH.

[Capt Quentin McHale]

clark y,


I think your boost pump problem is different to hosseins as in, his pumps were operational (except for possible boost pump chk valve failure/s) and I think you too may have had chk valve failure on the other wing with the two operational pumps. But you neglected to explain what happened with fuel tank qty indication once in cruise.


With regards to hosseins fuel temps, 3 temps are above zero and 1 temp below zero. I tend to think a false/faulty temp sensor indication on right outboard tank. My reason being that all tanks have had the same amount of "cold soak" while airborne, all be it, it was a short flight and not really long enough for a good cold soak. As far as the warm fuel and IDG theory, it doesn't happen, fuel does not return to the tanks from the engines.

[Goldenrivett]

Capt Quentin McHale,
As far as the warm fuel and IDG theory, it doesn't happen, fuel does not return to the tanks from the engines.
Please see Fuel Recirculation System | IDG Cooling (http://www.efbdesktop.com/fuel/sys-9.3.0.html)
& Page 115 of http://www.academia.edu/8535109/Training_Manual_A319_A320_A321 (http://www.academia.edu/8535109/Training_Manual_A319_A320_A321_ATA_71-80_ENGINE_CFM56-5A_ATA_30-21_AIR_INTAKE_ICE_PROTECTION)
Lufthansa Technical Training table suggest that up to 500Kg/hr can be returned to the outer fuel tank if the IDG oil Temp >93 deg C.
If the fuel pressure was greatest from the tank pump in the RHS, then fuel could be transferred into the LHS outer fuel tank via the IDG cooling flow mechanism as clark y suggests.

[Uplinker]

As far as the warm fuel and IDG theory, it doesn't happen, fuel does not return to the tanks from the engines.


Ermmm, yes it does !

[Capt Quentin McHale]

Goldenrivett, Uplinker and clark y,


You are indeed correct. Apologies, was in Boeing mode....

[clark y]

Capt Quentin,

With my problem, the fuel went out of balance by about 500kgs in about 20mins(top of climb). After that we applied the imbalance checklist. Can't remember how long it took to rebalance the fuel but I do remember it took a lot longer than expected.

[Lantirn]

The answer is in the FCOM.

FUEL CTR PUMP 1 (2) LO PR, although not directly linked to the above scenario, see the note.

A fuel imbalance may occur, if the performance of the pumps of one wing is different from that of the other wing......
....In this case, apply the fuel imbalance procedure, as required

[fruitloop]

Just a few silly questions here
1."Why did you have fuel in the centre tank when you load total was less then 12.000 kg"s.??.pre take-off..
As someone has already mentioned the pump out-puts can vary a fair amount (including the centre pumps)Which incidently have the same output pressure as the wing pumps but are fitted with a higher pressure output check valve..
2."Why did you elect to turn the inboard wing tank pump off as opposed to the outboard.?" The Inboard pumps have a inbuilt "scavenge feature"
3."Did you notice if the IDG temp on Eng 1 was above 104 Degress C..?
"Wing tank fuel temps indicate that there was a lot of "Warm Fuel" returning.

[Microburst2002]

Lantirn that's a good reference!

Vilas: regarding the EFATO ECAM. I always thought that the reason for the IMBALANCE line in the ECAM was because of a possible leak due to a rupture of a line or hole in a tank, like a way to cater for an uncontained failure situation.

Like someone said above, "best pump wins".

Most importantly: don't invent procedures, specially those related with fuel.

I had a similar scenario. A 4 hour flight, full house, an imbalance was developing. Fuel checks and leak check confirmed everything OK, except the umbalance, progressively increasing. Captain said do nothing until ECAM comes. It came after a good deal of flight with "cross controls" (slip angle to the left, couple of degrees to the right).

I think it was because of a center pump performing way better than the other, so one inner tank started using its fuel way earlier than the other, to the point of reaching the ECAM trigger point.