Diagnosing Airbus FMGC Faults

[Cheapshoes]

Diagnosing Airbus FMGC Failures



Our MEL has multiple options relating to FMGC failures, including failures of the FM and FG segments and various other specific elements therein, along with despatch with single FMGC.

Other than “1 FD 1” FMA and “Set Offside Range” what other indications are there of an FMGC failure and, more specifically, what can we use to guide us in deducing which element has actually failed and therefore which is the appropriate MEL section and procedure?

It could be an absolute minefield on a line check and any tips would be very gratefully received.



Thanks.

[spannersatcx]

look at the message list in the front of the MEL that will tell you what MEL item is appropriate.
Or write it in the log and let the engineers determine what the failure is and what MEL to apply.

[Cheapshoes]

There are no failure messages for many instances, which is why the discussion was instigated specifically around diagnostics. Thanks anyway.

[rudderrudderrat]

Hi Cheapshoes,

If you can't work out which bit is broken, then simply assume the whole of FMGC1 or FMGC2 is US and apply the appropriate procedure.

I've had the FMS part fail once during flight - but the AP could be engaged in "simple" modes like HDG, VS, OPEN CLIMB / DESC, ALT - all with manual thrust.
It was like a good day out on 707s.

[Megaton]

I've had double FMGC failure a couple of times. Once near top of climb which was a bit of a non-event and the other at high speed on the takeoff roll. The first time, we had to reset the FMGCs manually but the second time they eventually rebooted themselves. Both were a while ago but from memory the first signs of trouble were resynching messages on the MCDU followed by loss of FDs, A/T, A/P, characteristic speeds. For the takeoff roll case, there was some guidance on a "F/D Off" takeoff which is essentially similar to the double FMGC failure.

[TURIN]

If there is no fault message then use the TSM Observed Faults section. It should have references to various observed failures and how to trouble shoot accordingly.

Most organisations employ staff trained to do this.

[Cheapshoes]

Thanks for the replies all.

Turin; our Co., a credible UK airline, has operated the aircraft for nearly two decades and FMGC failure recognition remains poorly understood, so I have no compunction about seeking wider advice. Be well.