A/C dispatch with outer tanks leaking - Use of MEL
 

Recently I came across a very strange hypothetical MEL application scenario that I’d like to share with you.

A320 in transit at outstation. After refueling fuel is leaking from the outer tank access panel behind the outer flap track fairing (outer tank). Fuel leak rate is out of AMM acceptable limits. According to an engineer the airplane can be dispatched with the OUTER TANKS EMPTY and the all TRANSFER VALVES deactivated open permitting the flight to be conducted under MEL 28-15-01A (LH wing transfer valves) and 28-15-02A (RH wing transfer valves). According to his rationale, forcing the transfer valves to open by pulling out their CBs is necessary in order to prevent fuel returning from the IDG oil cooling circuit from accumulating in the leaking outer tank. The leaking point is way off the point of the fuel return from the IDG. That means, the fuel return from IDG flows from the outer tanks back to the inner tanks and there is no risk of leaking fuel as the outer tank is always kept almost empty. Needless to say that the abnormal fuel distribution (outer tanks empty) should be reflected in the load sheet so that CG can be precisely calculated and the A/C is dispatched for one flight only to return to base.

Although the proposed solution sounds technically correct, I expressed my disagreement based on legality issues. First objection, an engineer is not authorized to use the MEL items to configure the airplane at will. From a legal standpoint the engineer simply follows the MEL and the flight crew accepts. The item MEL 28-15-01A, for example, can be used ONLY when one or more TRANSFER VALVES have FAILED open and not to give solutions to other problems (outer tank fuel leak) by forcing the TRANSFER VALVES to fail unless there is another MEL entry cross reference to this specific MEL entry. There is no room for improvisation in MEL issues. Second objection, to my knowledge, there is no provision for dispatching the airplane with empty outer tanks. That means, the engineer is not authorized to distribute the fuel in the tanks at will. Fuel distribution before departure should fulfill certain criteria. For the aforementioned reasons I believe that although the proposed solution seems to be technically sound, the airplane should either be dispatched under a special permit granted by the CAA to fly without passengers or grounded until is repaired.

Any comments?

just to throw another one in , on a bigger bus with trim tank or 747-400, MEL wouldn't allow you to inop it for a fuel leak but you could for another problem i.e valve etc which is effectively the same. I don't disagree with your logic but in other areas MEL is used as a workaround for dispatch .

He has offered the aircraft for service with a fuel leak still outside the limits of the AMM. If the AMM wished him to dispatch in this condition, it should have said so...

Illegal.

They should use this - AIB approved - method:
Fuel Tank Leak Quick Repair kit

"outer tank is always kept almost empty"..... WRONG !!! Try again !!

Why is the tank leaking? There are many reasons, but one is structural failure. Surely before anyone would accept any kind of MEL, permission to proceed etc ,a full structural investigation would occur??

Wunwing

Not a starter, the leak is out of limits and the MEL refers to a different system..... so no.

"Creativity" rears its ugly head again...

"Creativity" rears its ugly head again...

Relevant point.

The MMEL has been generated by knowledgeable folks after due process. The document certainly doesn't cover all situations, rather those considered by the OEM to be of use so there is opportunity to tailor it in the MEL process stage.

The MEL should be conservative with respect to the MMEL unless authorised by the relevant Regulatory Authority (hopefully, in a competent process).

It follows that the MEL words be followed on the line in a Step A, Step B .. fashion.

The line pilot doesn't necessarily have all the information which needs to go into varying the MEL provisions.

I don't make irrelevant ones, John.