A320F FUEL LEAK procedure : why CTR pumps off if no fuel in CTR tanks

[C.M]

With respect to the QRH FUEL LEAK procedure : In the second case in which a Leak from engine/pylon is not confirmed or leak not located , the procedure has you switching the center pumps off as a means of trying to determine if the leak is from the center tanks or from a wing/engine . Out of curiosity, why does the procedure assume the you have fuel in the center tanks ? That is it to say if there is no fuel in the center tanks wouldn’t it have made sense for the procedure to start like “ IF FUEL IN CTR TANKS .......CTR TK PUMP 1 .......OFF ,CTR TK PUMP 2.....OFF , instead of switching pumps off like a fool without a reason ?

Is there something that I am missing ?

[FlightDetent]

I seem to recall an explanation that an internal leak, INR -> CTR is also a possibility. This just from the top of my head, without checking and reviewing the ABN / QRH.

Does that help with your dilemma?

[Dave Therhino]

I think he's asking why does the procedure say to turn the pumps off when under some conditions they may already be off. I suspect the procedure was written to be as simple as possible.

[FlightDetent]

I think he's asking why does the procedure say to turn the pumps off when under some conditions they may already be off. I suspect the procedure was written to be as simple as possible. Agreed, not too many forks in the logic.

However his suggestion is for less actions, another well respected criterion.

It can be both what we said, as the pumps on the center tank are either
- push-buttoned active but de-energized automatically with an empty tank
- push-buttoned active and running automatically if flooded
- push-buttoned off

If you were troubleshooting a leak which is dips fuel into the center tank, observing the development let's say for 30 minutes, you do not want the pumps firing up now and then, defying the purpouse of the excercise. (speculation, still did not check the ABN)

On A321 and shorter versions of recent modification (factory built), there are no center pumps but transfer valves which jet-pump the center fuel into the wing tanks (or maybe into the wing tank engine feeding line). Another angle to review.

Three things for sure:
​​​​​​The procedure is properly designed by smart people and done on purpouse as it is.
To a pilot the FCOM's System Description paints a kindergarten picture of the real technology installed
We will learn the reason and posibbly Airbus explanation once the daylight timezone revolves past vilas's location. 😁👍

[vilas]

All procedures are optimum procedures . One shoe fits all. But I tend to agree with CM and Dave. This procedure is like Fuel Leak for Dummies. It is ritualistic. When there's no fuel in center tank at all the fuel leak has to be from left to right inner tank or the respective engine and it will show as imbalance. The cross feed is always off. So one can directly move from here by finding out whether it's from tank or engine. But since the procedure is for all situation it considers fuel in center tank and possibility of cross feed being on. There is a small print note below the Leak from engine/pylon not confirmed or leak not located. It says:
Stop any fuel transfer, and then monitor the depletion rate of each inner tank, to determine if the leak is from an engine or a wing (case 1), or from the Center tank or the APU feeding line (case 2).
In A320 there is no fuel transfer and in our case case 2 is not applicable. We already know the side leak is from. So one can directly move for case 1.
And FD thanks for the complement.