A319
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 153
Troubleshooting; Distraction; Human-Machine Interface; Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft; Manuals
In cruise at FL370; VMC conditions; I noticed an 'STS' message.  Pressing the STS key revealed inoperative systems 'AP2' and 'Cat 3 Dual' I checked circuit breakers and confirmed none popped. I then noticed the Flight Director indication was 1FD1; and told the F/O (First Officer) it appeared his Flight Director was inoperative.  Next; the F/O's MCDU revealed 'OPP FMGC IN PROCESS'.  I went to the QRH and we confirmed a single FMGC failure on the F/O side.  We reviewed the checklist together and it allowed a 'system reset' both on the ground and in flight. I was hesitant at first; but weather was VMC to destination and I wanted to understand the system better. The checklist reset called for turning off both FDs before pulling CBs. We both read then reviewed the reset procedure and interpreted the checklist as pulling both the FMGC 1 and FMGC 2 CBs. This was wrong; as only the failed FMGC CB should have been pulled/reset.  I disconnected the autopilot prior to the F/O pulling the CBs and when the FMGC1 CB was pulled we received caution messages associated with loss of that FMGC. We quickly realized this was wrong and reset the CB; restoring power to FMGC1.  Because the FMGC dumped its data; we initially requested and received a heading to fly from ATC; then stepped through and restored the destination; route of flight; ZFW (Zero Fuel Weight) and pertinent info to the FMGC1.  We reviewed and verified all data against the flight plan as correct and continued normally to destination without incident. A maintenance log item was made for both the FMGC2 failure and the pulling/resetting of the CBs.Both the F/O and I misinterpreted the checklist reset procedure by resetting both FMGC CBs vice just the failed FMGC.  This occurred for me for a few reasons. The procedure has you turn off 'both' FDs and the current FMGC configuration involved both MCDUs which I believe led me to interpret both FMGCs would be reset. The wording on the checklist is vague and states 'open the affected system' CB; then lists (in all caps) both FMGC CBs. The word 'affected' is not emphasized; nor bold; nor defined; and together with the word; 'system' can be misread as plural or open to misinterpret especially since both FMGC CBs are listed next in all caps. The checklist title uses the word 'Failure' for the FMGC; and the Condition statement discusses a 'failed FMGC' yet the reset procedure does not use the word 'failed' but rather uses 'affected' which does not stand out.  I was unaware there is only one CB for each FMGC and incorrectly thought an in-flight reset would act much like a computer restart and not turn the FMGC completely off and erase the current data.  We have not had training in this area and the checklist has no caution addressing this. I had not done a system reset while airborne previously; but have done reset procedures on the ground with maintenance that involved pulling more than one CB for a system reset and this may have affected my misinterpretation. Lastly; we did not rush this procedure yet it did not prevent the error; therefore in the future I need to read a procedure more carefully and clearly.
An Airbus flight crew reported experiencing several flight guidance error messages related to a failure of the First Officer's Flight Management Guidance Computer. Due to some confusion with the QRH checklist the crew mistakenly opened circuit breakers for both FMGC1 and FMGC2. This error was quickly recognized and FMGC1 was restored to normal operation.