A320 Fuel leak procedure

[dustypfd]

Does anyone know the significance of the 3 tons in the last line of the fuel leak procedure.

It says when each wing tank gets down to 3000Kg to switch the centre tank pumps on.

Thanks

[TyroPicard]

This is part of CASE 2, where both tanks deplete at the same rate, suggesting a centre tank/APU feed line leak. Not sure that it is "significant" - perhaps just a sensible figure so that you start to use the Centre Tank fuel again to feed the engines and top up the wing tanks.

[aristoclis]

The center tank pumps were switched off as part of the investigation process, so that each engine is fed via its associated inner tank only.
Since it is determined that the leak is not from either inner tank nor engine/pylon (both inner deplete in a similar rate), what is left is either APU line or center tank. Supposing center tank leak I really see no reason why not selecting center tank pumps on (mode sel auto) in order to use at least some amount of the center tank. Waiting for full inner tanks to go below 3t, might lead to loss of center tank fuel, part of which could have been used. Auto mode would still control center pumps on-off to allow IDG cooling fuel return to the wings.

@Tyropicard

Actually even with full center tank feeding engines when inners are at 3t, I am not sure if fuel return is able to top up the wings again. I mean fuel has to be used also by the engines. On the other hand if center tank pumps were selected on after the investigation, inner tanks would remain full or almost full until center tank went empty (fuel either used or lost).

@dustypfd

Good question. I don't know the answer. Any help appreciated :}

[TyroPicard]

aristoclis
Actually even with full center tank feeding engines when inners are at 3t, I am not sure if fuel return is able to top up the wings again.Next time you fly with a reasonable quantity of centre tank fuel monitor the wing tanks to see what happens.

I say again - 3,000 kg has no significance as far as I am aware. It gives you time to monitor the leak for 30 minutes, and then reminds you to switch the centre tank pumps back on for the rest of the flight. It's really very simple.

[aristoclis]

Unless I intentionally turned off center tank pumps until inners decrease to 3000kg, I would never have the chance to find out in normal flights. So this is what happens normally: when about 500kg are used from the inners, auto mode turns on the center tank pumps again, so they top up again from the fuel return and center tank pumps come off. Have you noticed anything different? Have you actually seen even half full center tank with 3000kg in the inners in a normal operating fuel system?

And....yes it is really very simple, except: If there is no significance (I really can't find any either) in the 3000kg figure, why mention it in the first place? Would not a simple action -CTR TK PUMP 1+2 (CASE 2 paragraph) in the paperchecklist, regardless of inner tank quantity, be enough to remind the crew?

Suppose after your 30 minutes investigation you have 4.8 tons in either inner (30 minutes aprox. 1200kg burn if they were full when procedure started) and 2 tons in your center. Would you wait another 90 minutes to get to 3 tons in the inners before selecting center tank pumps on and use at least some amount from the center tank? That's what the procedure tells you. Is it really so simple?

[TyroPicard]

When reading Airbus FCOM absolute precision is so important... it's the inner tank we need to think about...

I never suggested turning off the centre tank pumps in normal flight ... but as you know they do have the capacity to top up the inner tanks and feed the engines. That is why you turn them off during the fuel leak procedure, so that you can diagnose accurately.

Your A320 inner tanks are bigger than usual! Normal capacity is about 5,400 not 6,000. Let's say you start the procedure with 4.9 T in the inner tank then the qty will be about 3.7 T after 30 minutes in the cruise.

But hopefully you will have already landed within 30 minutes (WHEN A LEAK IS CONFIRMED LAND ASAP) so you only need to turn on the center tank pumps when an inner tank reaches 3,000 kg. for a more distant diversion airfield.

[aristoclis]

Well, first of all thanks for the advice about precision.

But reading the FCOM precisely, did you find anywhere stated that when the center tank pumps operate the inners receive fuel from the center tank? I thought in that case center tank is feeding the engines and not the inners. Part of engine fuel is returned to the inners via the outers.

Why turning center tank pumps off at the beginning of the investigation process is crystal clear.

If this process leads to the conclusion that center tank is leaking (inners deplete at the same rate), it would make only sense if center tank had a certain amount of fuel. Center tank being not empty the inners quantity would be between 4.9t and 5.4t each at the beginning of the investigation process. Suppose crew is so slow that it needed 30 minutes to investigate, fuel burn from the inners during investigation and while center tank pumps off, would be about 1.2 t total. This would leave the inners with about 4.3 to 4.8t each. So again, why wait for 3t and not use immediately whatever is left in the center tank?

And suppose you do end up with 3t in either inner, you still think that you can top up your inners from a leaking center tank? That' s a total of 4.8t needed from the fuel return valves :rolleyes:
And how am I supposed to find it out if this is possible in a normal flight if not by switching off the center tank pumps off and wait the inners to drop to 3t ? Not a good idea, is it.

And by the way, not my inners but your fuel flow is bigger than usual.

[nnc0]

My own comments

1 - If your dealing with Case 2 (CTR TK concern) the leak is presumed to be in the plumbing, not the tank.

2 - You're supposed to land ASAP (nearest suitable airport). If the leak is CASE 2 then leave the fuel in the CTR TK unless it's absolutely neccessary to use it. If it is needed to make the nearest suitable field then the 3000 kg figure assumes a worst case scenario of an almost full CTR TK and allows for full transfer, or as much as possible, from CTR TK without risk of spillover into the surge tank. If there was significantly less than full fuel in the ctr tk and space was available for it in the inner tks then you could indeed select the CTR TK pumps on again but why bother unless you need the fuel. You're just wasting fuel out the leaky plumbing.

[aristoclis]

"If it is needed to make the nearest suitable field then the 3000 kg figure assumes a worst case scenario of an almost full CTR TK and allows for full transfer, or as much as possible, from CTR TK without risk of spillover into the surge tank."

If I remember well, with mode sel auto and center tank pumps on there is no risk of spillover. Auto mode switches the pumps on and off to keep inners between full and underfull sensors. So using center tank fuel as much as possible is achieved by selecting center pumps on immediately with mode sel at auto.

Anyhow, I really enjoyed participating in this conversation. Fly safe.:ok:

[Field In Sight]

Just been reading this drill for my next sim and was also confused as to what the 3 ton condition was for.

I agree that the auto feed system would allow for the centre tank fuel to be used first. Maybe it is like this to allow for dispatch with manual only control of the centre tanks.

[Swedish Steve]

I just read this, and not having a FCOM, I wonder if Airbus is trying to make one procedure for all small Airbusses.

Remember that on the A319 and A320 the centre tank pumps feed the engines. On the A321 they feed the wing tanks.
So maybe you wait for 3 tonnes, so that when you turn the pumps back on there is room in an A321 wing tank (no inners and outers on an A321!) to take the fuel?, and the A320 drill is kept the same?

[Delta Papa]

Present Scenario: There's a fuel leak from the inner right side tank with no fuel in center tank. There`s a caution on QRH 2.08A "Do not open FUEL X FEED valve, even if requested by another ECAM procedure". That means that engine 2 will stop with fuel on the left side? The diagram on FCOM 1 is no so clear for me. I understand that X FEED means that engine is feed from the opossite tank and not right tank is feed from the left tank. :bored:

[FlightDetent]

The right side leak is observed by indication of the right tank. It is entirely possible that the leak point is not in the tank itself but it in the feed line of engine no. 2. Opening the crossfeed could expose the left side fuel to the leak point resulting in unnecessary loss. Even if the right wing tank had been ruptured you still would have loss of left wing fuel through return flow via outer to inner right tank and then out - with open crossfeed.

In order to prevent these the Xfeed is kept closed and engine no 2 will starve out once right side fuel depletes through consumption and leak. You get to keep all available left side fuel for eng no 1 in the ensuing OEI case.

[UTW]

Any more theories on why the figure of 3000 Kg is specified?

[rudderrudderrat]

Hi UTW,

Crikey - this is an old one you've dredged up.
Any more theories on why the figure of 3000 Kg is specified?
Probably a compromise in order to give you time for analysis and to comply with:

"FUEL MANAGEMENT
Tanks must be emptied in the following order :
center tank then wing tanks"
so as to take care of wing bending loads.

If the fuel tank is leaking, then best to use it rather than loose it, since you can't pump wing tank fuel into the centre tank and waste it like the Azores Transat.

[UTW]

Thanks RRR,
Yeah...it is an old question.
It came up in the sim the other day but I didn't have an answer.

[vilas]

Airbus itself was asked this question in 2007. Their engineers could not find any reason so they said this line will be removed unfortunately it is 2012 and it is still there. So you have to wait.

[Natstrackalpha]

I love using my HOWGOZIT?

Better on Long Haul than short haul as you may be devoid of time.

I lamenated mine and use a chinagraph on it then rub out the marks after use, with a wet finger.

This is a nice way of determining a leak before it becomes apparent in other areas.

I know you know, but for those who may have missed it in their studies;

draw a line vertically in the left hand column of A4 Landscape not Protrait -

and another line (the horizontal axis along the bottome of the graph to be . .

Left hand line (vertical left margin is your fuel in ,000kg or lbs if you are using lbs of fuel . . .

Along the bottom line write your distance in NM or KM if you must . . . (!)

the top of the left line is your total fuel on board minus taxi, takeoff, clb, or not if its a long step . .

in the cruise, soon, hopefully,

Draw a nice straight line from the fuel you have got at TOC all the way down to . .

Dest - at which point you intend to arrive at Dest with your pre-planned Dest fuel and all its reserves and all that.

As you proceed in your flight along track, check FOB against miles gone (along the bottom line in NM)

Cross the two points from the fuel amount FOB where it intersects the NM gone DIST and where the vertical and horizontal intersect draw a little asterisk or a tiny cross "x"

All along your route, your Straight line you drew diagonally from fuel line to Dest will have the little "x"s on it, above it or below it. If below it, of course, you are using more fuel than pre-planned if above the diag line then you are using less fuel for that geographical position. Removing the obvious considerations en-route such as head wind / tail wind or into the teeth of a Jestream, temp, etc., and all the rest of it - you can readily determine if you are illogically using too much fuel.

If consumption is high `despite` taking into consideration the above calcs and wind then - chances are you have a leak or a very thirsty engine. the latter may be determined by your GFF - of course.

You could also get dweeby and simply determine SFF by dividing total GFF by the Groundspeed to give you Kg per ground NM..... Kg/gnm or... lbs/gnm if you have a President.

[capt937895565]

When a fuel leak is detected, but not located, the fuel leak procedure requests the flight crew to set to OFF the center tank pumps. In the case of a leak from the APU feeding line, or a leak from the engine feeding line, the center tank pumps are set to OFF and then to ON again when one wing tank contains less than 3 tons.

~~What happens in the case of an important leak?~~

In the case of a leak from the engine feed line located in an inner tank, fuel would spill from the center tank into this inner tank.
Should the engine feeding line breakage be important, the flight crew would not detect a leak, as the engine would shut down and/or there would be a “CTR TK PUMP 1(2) LO PR” caution triggered, leading to procedures that will result in setting to OFF the affected center tank pump, thus stopping this leak.

~~What happens in the case of a small leak?~~

The crew may detect the possibility of a leak in case of a less important breakage, if they notice that a fuel imbalance is developing.
On the affected side, the engine is still fed and no low pressure is detected on the center tank pump. Fuel spills from the center tank to the inner tank.
In this case, if the crew applies the fuel leak procedure, the center tank pumps are set to OFF. Both inner tanks will deplete at a similar rate (Case 2 of the fuel leak procedure).
When the fuel in one inner tank has depleted to 5 tons, the following will occur:
Per design, when one inner tank is less than 5 tons and there is fuel in the center tank, the “FUEL AUTO FEED FAULT” caution will trigger on the ECAM.
As the center tank pumps are OFF when the alert triggers, an action line on the ECAM will require the flight crew to set the center tank pumps to ON again.

~~Then, why is it necessary to have the “3 tons line” in the fuel leak procedure ?~~

As the crew has been told by the FUEL LEAK procedure to set the center tank pumps to OFF, it has been considered that some flight crews might be confused, and would disregard the “FUEL AUTO FEED FAULT” and adhere strictly to the FUEL LEAK paper procedure. So they would not start again the center tank pumps when the “FUEL AUTO FEED FAULT” caution triggers and leave them OFF.
The “3 tons line” in the FUEL LEAK procedure has been introduced to cover this case. This line guarantees that the flight crew will set the center tank pumps back to ON, even if they previously disregarded the “FUEL AUTO FEED FAULT” caution.
This will allow the consumption of the fuel remaining in the center tank.

~~Why wait for 3 tons?~~

The pumps could be set to ON earlier, but this value has been chosen to cover also the remote case of a subsequent failure of the full level sensor in the affected inner tank.
In such a failure case, if the center tank pumps are set to ON early, there could be fuel spilled overboard, due to the fuel going from center tank to the inner tank through the line breakage and the full level sensor being inoperative.
So a 3 tons conservative value has been chosen, because at that time there is sufficient space in the inner tank to allow a transfer of fuel from the center tank to the inner tank (through the breakage in the feeding pipe) with a reduced risk of overflow.

[Lantirn]

Todays observation,

A320's QRH
A fuel leak may be detected, if:
‐ The sum of FOB and FU significantly less than FOB at engine start or is decreasing, or
‐ A passenger observes fuel spray from engine/pylon or wingtip/sharklet, or
‐ The total fuel quantity is decreasing at an abnormal rate, or
‐ A fuel imbalance is developing, or
‐ Fuel quantity in a tank is decreasing too fast (leak from engine/pylon, or hole in a tank), or
‐ The Fuel flow is excessive (leak from engine), or
‐ Fuel is smelt in the cabin.
‐ The destination EFOB turns to amber on the F.PLN (or on the FUEL PRED) page, or
‐ ″DEST EFOB BELOW MIN″ appears on the MCDU scratchpad.

A321's QRH
A fuel leak may be detected, if:
‐ The sum of FOB and FU significantly less than FOB at engine start or is decreasing, or
‐ A passenger observes fuel spray from engine/pylon or wingtip/sharklet, or
‐ The total fuel quantity is decreasing at an abnormal rate, or
‐ A fuel imbalance is developing, or
‐ Fuel quantity in a tank is decreasing too fast (leak from engine/pylon, or hole in a tank), or
‐ A tank is overflowing (due to pipe rupture in a tank), or
‐ The Fuel flow is excessive (leak from engine), or
‐ Fuel is smelt in the cabin.
‐ The destination EFOB turns to amber on the F.PLN (or on the FUEL PRED) page, or
‐ ″DEST EFOB BELOW MIN″ appears on the MCDU scratchpad.

Item in bold, is missing in the A320's. Mindblowing...

Just thinking that this note was supposed to be for the A320's fleet and not the A321s?

Putting facts down,

We are talking about fuel from the center tank supposed to flow to an engine, and due to a rupture it finally fills the respective inner tank with the risk or overflowing.

In my opinion, such a rupture would be possible in the 320's only.

A rupture in the pipes that could result in overflowing inner tank fuel is not possible in 321's, as 321's dont have such pipes in the inner tanks. Fuel is transfered with the help of jet pumps, and engines are fed directly from the wing tank pumps.

:ugh:

[LEVEL600]

Both A320/321 have feeding presurized plumbing inside CTR/CTR TRANSFER tank. I think there is space for such scenario if double problem exists - leak from a feed line inside CTR tank and full sensor/transfer valve fault. In such situation can be fuel transfered from one inner to another via CTR tank and its tansfer system on 321...at least theoretically :)

[vilas]

capt937895565
What you stated is correct and I received the same reply from Airbus. Interesting thing is the question about the significance of 3Tons was asked by one of Airbus industry instructor himself and the answer given by them was that engineering cannot not find any significance about it so they plan to delete it. But they have not deleted even now after 7years. When I asked them this question they gave me detailed reply as yours. Then I asked them to remove the earlier one from FAQ. They replied that the respective department has been instructed. But they have not done it.

[Microburst2002]

Maybe the guy who made the decision left the company and now they don't know why that line is there, so they don't want to touch it:}

[sonicbum]

folks, talking about fuel... the newest A320 MSN have a maximum allowed fuel imbalance that is different between takeoff and in-flight/landing. Where does that come from ? On the "old" MSN the tables do not differentiate between different phases of flight.
Thanks

[dream747]

How do I correctly interpret the second case in the A320 fuel leak procedure, where it says "Leak from engine/pylon not confirmed or leak not located"?

This part of the procedure calls for the actions to be done to determine if the fuel leak is from the engine, wing, or center tank. If cabin crew and passengers or the Pilots themselves observe a fuel trail from the wing away from the engine and pylon; fuel SD page shows the respective side fuel decreasing, will I be right to say that we can safely assume that the fuel is leaking from the wing tank, without having to run this part of the procedure of shutting down the respective side engine etc? My instructor says we should still run this procedure regardless, but It seems obvious to me it's from the tank in this case. Unnecessary to apply this procedure to conclude the leak is from the wing. Any objections?

[vilas]

dream747
The fuel leak procedure is a bit ritualistic. The procedure LEAK FROM ENGINE/PYLON NOT CONFIRMED or LEAK NOT LOCATED also assumes that there is fuel in center tank. When there is no fuel in the center tank then it is straight forward case of leak from one side because the cross feed is always off and fuel imbalance will also be developing. But still leak can be from engine or tank. Even if leak is from engine it can be from upstream or down stream of fuel flow meter. In case of fuel leak down stream of FF meter the sum total of FU+FOB will match fuel at departure but the FF on that side will be high but in upstream leak case it will not match. So there are variables and to avoid too much thinking and hasty conclusion it is safer to run through the procedure.

[dream747]

Thanks Vilas for the insight.

Are we allowed to use the fuel cross feed after ascertaining that the fuel leak is from the wing tank? Procedure says do not apply fuel imbalance procedure, but does it mean we cannot use the crossfeed as well? The confusion I have stems from the fuel diagram which is not very clear to me. With the fuel crossfeed on, does fuel come from the good wing tank and goes into the opposite leaking tank, or just straight through into the Engine of the leaking side tank?

[vilas]

If fuel leak is identified but not stopped you cannot use cross feed. There is no inter tank transfer but I guess pipeline used is same. Most important thing after leak is identified is LAND ASAP. Select a diversion within a range without leaking side fuel quantity. Cross feeding is not required for balancing. Landing can be done with one side full and other side empty.

[Citation2]

One small note about the procedure:
It says that if fuel leak stops xfeed can be opened to rebalance fuel quantity or to enable use of fuel of both wings.

Opening xfeed for both wings feeding one engine:
Well the truth is opening the xfeed will further aggravate the imbalance
Let s imagine 5000 on left side and 2000 on the right side , once the xfeed is open you might end up in 5000 on left side and 0 on the right so a greater imbalance.

About rebalance:
I dont understand how Airbus can seriously call for a rebalance as imbalance procedure calls for switching off the fuel pumps on the heavier side

Now with one engine inoperative would you switch off the fuel pumps on the live engine just to rebalance?
And by just xfeeding imbalance will increase. So how rebalance is at all possible?

The only reason to xfeed should be to reach your airport if you need that fuel. As for rebalancing and xfeeding something is definitely wrong in the procedure.

Just to clarify things about imbalance, i will mention the famous never ending engine failure scenario we usually practice at v1.
The live engine has been operating on its respective wing tank side for a while, therefore the operating engine side has a lower fuel quantity that the inop side and xfeeding make sense and could hep

On the fuel leak scenario the good side has a higher fuel quantity than the "leaking" side therefore xfeeding will further increase the imbalance.

Therefore whenever the good side has a higher fuel quantity than the damaged side do not xfeed unless needed to reach an airport.

When the "live or good" side has a lower fuel quantity than the damaged side (engine failure case) xfeed will help to protect the good side
That was for xfeed.
As for imbalance procedure , in my opinion, this should only be considered with 2 "healthy" sides as it involves switching OFF pumps on the only remaining operative side.

[vilas]

Citation2
I dont understand how Airbus can seriously call for a rebalance as imbalance procedure calls for switching off the fuel pumps on the heavier side
If you read the procedure wrongly then you wouldn't understand. The procedure calls for switching off lighter side fuel pumps and not heavier side. This is one of the simplest of procedures and it appears you have tied yourself in knots over it.

[Escape Path]

dream747
The fuel leak procedure is a bit ritualistic. The procedure LEAK FROM ENGINE/PYLON NOT CONFIRMED or LEAK NOT LOCATED also assumes that there is fuel in center tank. When there is no fuel in the center tank then it is straight forward case of leak from one side because the cross feed is always off and fuel imbalance will also be developing.

Our usual routes are short enough to not have fuel in central tank. However we practiced an scenario in the sim in which we are dispatched with one engine driven generator inop, so we have to use the APU in flight. That's another way to get to case two even if you don't have any fuel in the centre tank (APU feeding line).

Having this fault in that particular scenario adds another intricacy to whole thing as, in theory at least, you might action case one first, which instructs you to shut down the leaking side engine which is always, you guessed it: the side with the live generator. This would leave you with just one gen alive (APU) and OEI for nothing as this is not where the leak is. What skipper and I decided to do was to read the rest of the procedure but not performing any actions to try and find some logic in the procedure before doing anything. After discarding the symptoms for a possible engine/pylon/wing tank, we just skipped case one altogether and went straight to case two, shut down the APU and that was it.

@citation2

One of the lines on ECAM after engine failure is "Imbalance... Monitor". It is my understanding that in the past that line used to say "Xfeed... Open". After several fuel advisories doing initial training (especially if after flying the EOSID we'd fly a single engine go around for another EOSID), if opening the Xfeed such advisory wouldn't pop up. Now, I'm not sure how it works since during the whole procedure you don't turn the receiving (not supplying) tank pumps off, but it works and it keeps the tanks balanced. Although it's not important on the A320, as vilas said, because you can land with one wing full and one wing empty without any issues

[IcePack]

The old qrh said open the x-feed after an engine failure after confirming no leaks. This procedure worked well on the sims. Sims are a bunch of electronics which meant both sides were giving equal fuel pressures. The real pumps have slightly different output pressures. On the real aircraft with all wing pumps running & crossfeed open it is possible that the live engine may be just using all the fuel from either wing. The (new) qrh procedure of monitoring the fuel imbalance makes better sense as long as it is not forgotten. Funny how long it took airbus to change the procedure however.

[Goldenrivett]

On the real aircraft with all wing pumps running & crossfeed open it is possible that the live engine may be just using all the fuel from either wing.
True. But since the design concept is to "hide" the fuel distribution from constant view, then ECAM has been designed to prompt the crew to switch the appropriate fuel pumps off and on before running a tank dry (700 kgs LO limit).

[IcePack]

Yep that is how I understand the methodology. As long as distraction does not cause you to ignore the warning.

[Citation2]

Villas , please next time you go the sim try to balance your tanks after a fuel leak and one engine shutdown. If you succeed in it I ll be happy to learn from you.
Again by opening the xfeed in a fuel leak there is no way to rebalance the tanks but simply increase the imbalance.

Very good thanks for spotting my mistake regarding the fuel imbalance , indeed the lighter side has to be switched off. So if you want to apply the imbalance procedure in a fuel leak you will switch off the fuel pumps on the "leaking lighter side " and send the fuel from the good side to the tank leaking ?

No way to rebalance . X feed is not made for that purpose but to consume from a dead side , thus further increasing an imabalance .

As for the engine failure scenario itself it is totally different as the "live side" has lower fuel than the dead side, as the live engine has been operating for a while on only one tank, then opening the xfeed will help to rebalance and consume from the dead side full of fuel.

My point is , if the live side has lower fuel than the dead side (engine fail at v1 only), xfeed will help
Fuel leak scenario , dead side has lower fuel than live side , xfeed will increase the imbalance.

[vilas]

Citation2
I think you read the fuel leak procedure in a hurry . First you mistakenly assumed that the procedure requires to switch off heavier side. Now also you are mistakenly assuming that it asks you to balance the fuel if a leak is located and stopped with engine shut down. No! It doesn't. All it says is as below:
 If leak stops: ENGINE LEAK CONFIRMED
FUEL X FEED.............................................AS RQRD
DO NOT RESTART AFFECTED ENGINE
True you may have less fuel on the dead side because of fuel leak but nobody asks you to balance. Select your diversion and continue there. When live side fuel becomes less and if you need dead side fuel then open the cross feed and switch off lighter side pumps. The procedure is called imbalance procedure but in this case it is not for balancing. As for as the imbalance bogey is concerned FCOM below:
Note: There is no requirement to correct an imbalance, until the ECAM fuel advisory is displayed.