A320 X-Feed and Landing [Archive]

A320251N

3rd Oct 2020, 18:57

Hi there guys !

Please, could you give me your opinion in the following ?

Let's say you're in an OEI scenario, just about to pass the IAF of the procedure (after a previous OEI go-around), and get an ADV on FUEL SYSTEM with the drifting parameter being the fuel quantity in the dead engine's wing (live engine wing with something around 750kgs of fuel).

Would you delay the approach to perform the FUEL IMBALANCE procedure ?

As per the limitations, there are no controlabilities issues caused by such situation. Also, if you elect to perform the procedure at this time you will end up landing with the x-feed valve opened and the pumps of the live engine off. I never saw any kind of note/caution/warning/limitation saying that such is not allowed, but it feels odd for me. If I recall correctly it's forbidden in the 737 (yeap, I know, two different worlds).

Or would you just start the approach having in mind / discussing with your colleague that the IMBALANCE QRH procedure is one of the first things you will have to perform following another GA ?

Thanks in advance.

Goldenrivett

5th Oct 2020, 14:47

...
Would you delay the approach to perform the FUEL IMBALANCE procedure ?

I would not delay the approach with "LAND ASAP" displayed.

However, during my systems S.A. when I looked at the fuel page, I would determine if there was a fuel leak or not and recognise that with time the fuel imbalance will get worse due to S.E. operation. Provided there was no fuel leak, I would discus with my partner that by opening the fuel cross feed we may delay the ECAM FUEL IMBALANCE and at the same time ensure that all the fuel on board was available to my only operating engine.

Check Airman

5th Oct 2020, 15:15

1. No we’re not delaying the approach for a fuel imbalance

2. We’re certainly not turning off the pumps on the good engine just because the screen says so.

With 750kg in one wing (even the low wing), what is this other go around that you’re talking about?

vilas

5th Oct 2020, 16:38

Before the first approach the fuel from dead side should have been used more to create favourable fuel situation in live side tank. But since it wasn't then you can apply the procedure open the crossfeed. Switching off live side pumps is not that bad as it appears because it's not gravity feed. Fuel is comming under pressure from left side fuel pumps.

mantoga_srs

5th Oct 2020, 23:10

With LAND ASAP displayed, I won´t even think about performing a go around for this reason. In my opinion. flying with OEI in a two engine aircraft is a real mayday. Some people would say it is not a mayday but a pan-pan. This is another discussion...

A320251N

6th Oct 2020, 01:06

Hi there guys...

Thank you very much for your opinion and insights.

All the best.

vilas

6th Oct 2020, 04:58

I would not delay the approach with "LAND ASAP" displayed.
Actually the terminology fuel balancing is misleading. There's no need to balance fuel but here you may want to use the fuel from that side. Although there's no need to delay the approach to use the fuel from dead side LAND ASAP especially amber includes whatever it takes before landing.

Yeah nah

6th Oct 2020, 09:01

Ideally with one engine inoperative you should actively manage your fuel balance state and don’t wait for the advisory or ECAM to trigger the fuel balance procedure and this should avoid unwanted distractions on approach. If circumstances haven’t allowed you to do that then providing you have sufficient fuel in the feeding tank accept the imbalance and land.

For Airbus there is no limitation on landing or go arounds whilst still cross feeding with one engine inoperative. Certification requirements don’t allow takeoff with both engines feeding from a common tank to avoid multiple engine failures due to contamination or a fuel delivery type failure. I would avoid a cross feeding for approach and go around with both engines operating for the same reason but not in the OEI case.

Fursty Ferret

6th Oct 2020, 09:24

You're not trying to balance fuel in this scenario. If there's more fuel in the dead side then there's obviously not a significant leak, and with 750kg on the live side even if there is a leak you'll need the other tank's fuel regardless. So that's my logic, and I'd just open the cross-feed and carry on with the approach. I wouldn't switch off fuel pumps - I'm not trying to correct the imbalance, I just want the remaining engine supplied with fuel.

Max Angle

6th Oct 2020, 09:34

Quite agree with Fursty, did it for years in the sim without and issue but now my outfit want you to go through the whole fuel imbalance procedure and not just open the x-feed which needlessly increases the workload in an engine out situation and could quite easily lead to the remaining engine running dry in the event of a go-around etc. No idea if the change came from Airbus or our trainers, suspect the latter as keeping it simple is not one of their mottos!

compressor stall

6th Oct 2020, 09:55

I asked this question of Airbus - re after the engine failure determining no fuel leak just turning X feed open and leaving it.

Airbus's reply seemed obfuscatory - talking about the fact that you will get an imbalance anyway as the pumps may draw at different rates. They didn't say you couldn't land with the Xfeed open - even though that was my question.

sonicbum

6th Oct 2020, 11:39

Airbus's reply seemed obfuscatory -

Really ? Very hard to believe ! :}

We have asked the very same question a few times over the years, answers were : "it is not forbidden" , "it is a possibility" , "refer to the fuel imbalance procedure"

:hmm:

mcdhu

6th Oct 2020, 16:15

If there is no leak (FU+FOB=Block fuel?), then the safest config of the fuel system OEI is X-feed ON and all pumps ON. With only 750kgs on live engine side and X-feed OFF (shut), that fuel will disappear quickly in the event of a GA. A320 CEO fuel burn is 4T per hour per engine in TOGA so you will burn 400kgs in 6 mins!
As to landing with X-feed ON, nowhere does it say that you cannot do it. All that happens if you do is that the X-feed memo on the ECAM goes from green to amber as you pass through 1500' RA.
Hope this helps.
mcdhu

A320251N

7th Oct 2020, 00:29

Citation2

7th Oct 2020, 10:01

sonicbum

7th Oct 2020, 11:43

Should you need to use the fuel from the failed side , you need to apply the fuel imbalance procedure.

By simply opening the X-feed, you might aggravate the fuel imbalance , and end up dry on the live engine side.

Fuel pumps have no clue about « the live side or failed side »
Fuel Pumps do not necessarily have the same delivery pressure , the best pump wins.

For that reason switching off the fuel pumps on the lighter tank is a must as dictated by the fuel imbalance checklist.

Provided You have assessed there is no fuel leak there is no issue with opening the crossfeed valve thus allowing all wing tanks fuel to be used on the live engine and avoid an imbalance and/or fuel starvation.

Fursty Ferret

7th Oct 2020, 11:50

For that reason switching off the fuel pumps on the lighter tank is a must as dictated by the fuel imbalance checklist.

In this case by opening the fuel cross feed we're treating left and right wing tanks as one single tank. Makes no difference at that point which pumps have the higher pressure or if fuel moves between tanks.

vilas

7th Oct 2020, 14:52

In this case by opening the fuel cross feed we're treating left and right wing tanks as one single tank. Makes no difference at that point which pumps have the higher pressure or if fuel moves between tanks.
If live engine pump pressure is higher then the purpose of using fuel from dead side is defeated. So follow the procedure and switch off the required pumps. There's no harm at all as the fuel from dead side is coming under pressure.

Citation2

7th Oct 2020, 15:11

In this case by opening the fuel cross feed we're treating left and right wing tanks as one single tank. Makes no difference at that point which pumps have the higher pressure or if fuel moves between tanks.

Considering the scenario where the live side has the highest delivery pressure ,you wouldn’t want to have the « dry side » in the live side. If « fuel pumps OFF » in the live side is an issue ,

Approaching fuel starvation you will get an ECAM FUEL L (R) TK PUMP 1 + 2 LO PR
prompting you to switch OFF the fuel pumps from the starved side anyway.

And then how will the transition occur ? No one can garanty a smooth feeding transition from the dead side with the opposite being dry

Fursty Ferret

7th Oct 2020, 19:49

If live engine pump pressure is higher then the purpose of using fuel from dead side is defeated. So follow the procedure and switch off the required pumps. There's no harm at all as the fuel from dead side is coming under pressure.

The scenario in question here describes an approach that's just past the IAF. Not the ideal time to be messing with fuel systems other than a quick risk assessment and confirmation of the fuel cross-feed.

I don't understand your "live engine pump" statement. Low pressure fuel is supplied to the spar, whether it's via the cross-feed or the live side tank. The pressure is boosted by the HP pump and unused fuel is returned to that tank, where it is once again available. Doesn't matter where it is - it's a closed loop and provided the pumps are on, fuel will be supplied to the engine. Some of it may indeed flow back through the pumps in the live side, but who cares? It's fuel.

I just wouldn't want the hassle. You can gravity feed via the cross-feed if you really have to.

vilas

8th Oct 2020, 04:57

The scenario in question here describes an approach that's just past the IAF. Not the ideal time to be messing with fuel systems other than a quick risk assessment and confirmation of the fuel cross-feed.

I don't understand your "live engine pump" statement. Low pressure fuel is supplied to the spar, whether it's via the cross-feed or the live side tank. The pressure is boosted by the HP pump and unused fuel is returned to that tank, where it is once again available. Doesn't matter where it is - it's a closed loop and provided the pumps are on, fuel will be supplied to the engine. Some of it may indeed flow back through the pumps in the live side, but who cares? It's fuel.

I just wouldn't want the hassle. You can gravity feed via the cross-feed if you really have to.
I meant live engine side fuel pumps. Gravity feed with OEI is not simple it requires bank towards live engine which on approch will complicate the matter. There's no issue with switching off live side fuel pumps. Even if you don't it should be fine as long as fuel pumps on the dead side are working.

Fursty Ferret

8th Oct 2020, 06:50

I meant live engine side fuel pumps. Gravity feed with OEI is not simple it requires bank towards live engine which on approch will complicate the matter. There's no issue with switching off live side fuel pumps. Even if you don't it should be fine as long as fuel pumps on the dead side are working.

The problem is that the fuel from the dead side will be pumped into the live side, but those pumps are off. In the low fuel scenario Airbus advice is to switch all pumps on regardless of the indicated tank contents, so there's no risk of inadvertent fuel starvation provided the cross-feed is open and all pumps are on.