A320 gravity feeding with loss of engine

[PL64]

Dear all, I am currently doing my type rating A320 and I do have a question about the gravity fuelling procedure in the QRH.

Let's assume the following scenario; on a short flight you loose 2 pumps (LH inner tank) on one side. Because of the short flight it is unlikely that you will spend more than 30 min above FL300 and you therefore initially feed ENG 1 through the X-feed valve as per ECAM. Because now both engines are fed from the RH tank, an imbalance is created. Upon reaching FL150 the X-feed tank will be shut per QRH as now the ENG 1 can be fed by gravity feed. At this stage an imbalance exists but as now the X-feed valve is closed the difference will remain constant.

If we follow the FCOM:

"If no fuel leak, and for flight with only one engine running (the engine being fed by gravity), apply the following..." and again in the extremely unlikely event that we would loose engine 2 (engine 1 now being fed by gravity only as the X-feed valve is OFF) we would have to start sideslipping in order to get the fuel from the rh side in the LH side by opening the X-feed valve? Why would you have to do that as in this particular case the RH fuel pumps are still operational and just opening the X-feed valve should, according my understanding solve the issue?

In the case of a failure of engine 1 (which seems a bit more likely since this engine is fed by gravity only upon reaching FL150), engine 2 would still be running on its RH tank with the operational fuel pumps. Here one could indeed consider the opening of the X-feed valve and sideslip in order to get the fuel from the LH side into the RH side as this scenario would be fuel critical and an imbalance would evolve quickly... But if I read the QRH it says that this sideslipping manoeuvre is for the scenario where the live engine is fed by gravity only (as I understand it, this would not be the case in this particular case).

Can someone explain as I am a bit confused :hmm:?

Thanks

[vilas]

Like any other failure after ECAM actions are completed a situational assessment needs to be done. Where you compare your options and evaluate risks and benefits of them. There are three options.
1. If you stay at original FL let's say 290, cross feeding the failed side you will create an imbalance which cannot be corrected and that side with active fuel pumps engine may be left with insufficient fuel for safe approach and landing or a flame out.
2. The second option is to descend immediately to FL150. That is about 5mts of descent which will not consume any significant fuel from same side. The fuel consumption at FL150 is not 250kgs more than FL290 for one hour of flight. This much extra you will always have.
3. Divert to nearer airfield.
This will only be considered if second option is not available.
So execute the second option.
Procedures do not take decisions for you.

[Goldenrivett]

In the case of a failure of engine 1 (which seems a bit more likely since this engine is fed by gravity only upon reaching FL150), engine 2 would still be running on its RH tank with the operational fuel pumps. Here one could indeed consider the opening of the X-feed valve and sideslip in order to get the fuel from the LH side into the RH side as this scenario would be fuel critical and an imbalance would evolve quickly...

You can't transfer fuel from tank to tank, you can only feed the tank fuel to the engines. In the scenario above, if you anticipate that you will loose No2 engine due lack of fuel in RHS tank yet have plenty of fuel remaining in the LHS tank, then it would be wise to turn off all fuel pumps, open the X Feed and gravity feed both engines. By Side slipping, the higher tank will preferentially gravity feed both engines.