Narrative:

In cruise at FL340; while PF (pilot flying) was entering data via atsu (air traffic service unit); heard warning for autopilot disengagement; also single chime repeating every 3 seconds or so; ECAM (electronic centralized aircraft monitoring) showed autopilot disconnect; auto throttle disconnect; indications showed thrust lock . Matched throttle lever angle to display; used instinctive disconnect switch on throttles; pressed autopilot disconnect button on control stick; then re-engaged auto-thrust and autopilot 1. ECAM read press landing elevation fault; set manual landing elevation. PF set manual elevation knob to +100 (elevation of destination). Captain mcdu showed FM (flight management) light illuminated. Selecting an FMGC (flight management guidance computer) button resulted in a wait for function; so PF selected mcdu menu button and then FMGC. Bottom scratch pad showed independent operation (of FMGC). Pfd (primary flight display) showed 1fd2; indicating both FMGC were functioning. First officer (first officer) mcdu had been deferred inop and MEL prior to pushback. Could only see fp (flight plan) page; and entries had no effect. Waypoints did not cycle through when passed; and distance did not count down. Dir; rad navigation; data; int; second keys showed no response to pressing. Cycled captain mcdu circuit breaker in accordance with (in accordance with) QRH with no effect. Again; in accordance with QRH and tomc direction; cycled circuit breaker for both FMGC one at a time. Still no effect. Three or four times later during flight; autopilot and auto-thrust systems disengaged; but was able to re-engage both. Informed ATC that we were unable to navigate via RNAV; and though cleared dct dhart waypoint; we would need a heading. Center assigned us a heading; direct the ZZZ4 VOR when able. Both sides were tuned remotely using the rmp (radio management panel). Center changed our arrival to the ZZZ1 [STAR] and then the ZZZ2 [STAR] to make things easier on us; requiring only that we track the ZZZ3 046R inbound. Then gave us vectors for the ILS 27 at ZZZ. The entire time we were talking with dispatch on VHF2 (until we lost contact) and communicating with dispatch and maintenance via ACARS. Aircraft responded to normal inputs via FCU. PF and pm (pilot monitoring) referenced manual for landing speeds and pm briefed ILS approach under visual conditions; including how to fly published missed approach. Normal landing and rollout and taxi to gate accomplished. In chocks; determined that FMGC1 failed; and with MCDU2 deferred inop there was no way to provide input to FMGC2.

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Original NASA ASRS Text

Title: An Airbus flight crew experienced a failure of the Flight Management Guidance Computer #1. This failure; coupled with a previously deferred Multi-Purpose Control and Display Unit #2; rendered the aircraft incapable of continuing to navigate in an RNAV environment. After assistance was requested from Air Traffic Control; headings were issued; and the flight proceeded safely to the destination airport.

Narrative: In cruise at FL340; while PF (Pilot Flying) was entering data via ATSU (Air Traffic Service Unit); heard warning for Autopilot disengagement; also single chime repeating every 3 seconds or so; ECAM (Electronic Centralized Aircraft Monitoring) showed Autopilot disconnect; Auto throttle disconnect; indications showed Thrust Lock . Matched throttle lever angle to display; used instinctive disconnect switch on throttles; pressed autopilot disconnect button on control stick; then re-engaged auto-thrust and Autopilot 1. ECAM read PRESS Landing elevation fault; set Manual landing elevation. PF set manual elevation knob to +100 (elevation of destination). Captain MCDU showed FM (Flight Management) light illuminated. Selecting an FMGC (Flight Management Guidance Computer) button resulted in a wait for function; so PF selected MCDU menu button and then FMGC. Bottom scratch pad showed Independent Operation (of FMGC). PFD (Primary Flight Display) showed 1FD2; indicating both FMGC were functioning. F/O (First Officer) MCDU had been deferred inop and MEL prior to pushback. Could only see FP (Flight Plan) page; and entries had no effect. Waypoints did not cycle through when passed; and distance did not count down. DIR; RAD NAV; DATA; INT; SEC keys showed no response to pressing. Cycled Captain MCDU CB IAW (in accordance with) QRH with no effect. Again; IAW QRH and TOMC direction; cycled CB for both FMGC one at a time. Still no effect. Three or four times later during flight; autopilot and auto-thrust systems disengaged; but was able to re-engage both. Informed ATC that we were unable to navigate via RNAV; and though cleared DCT DHART waypoint; we would need a heading. Center assigned us a heading; direct the ZZZ4 VOR when able. Both sides were tuned remotely using the RMP (Radio Management Panel). Center changed our Arrival to the ZZZ1 [STAR] and then the ZZZ2 [STAR] to make things easier on us; requiring only that we track the ZZZ3 046R inbound. Then gave us vectors for the ILS 27 at ZZZ. The entire time we were talking with Dispatch on VHF2 (until we lost contact) and communicating with dispatch and maintenance via ACARS. Aircraft responded to normal inputs via FCU. PF and PM (Pilot Monitoring) referenced Manual for landing speeds and PM briefed ILS approach under visual conditions; including how to fly published missed approach. Normal landing and rollout and taxi to gate accomplished. In chocks; determined that FMGC1 failed; and with MCDU2 deferred inop there was no way to provide input to FMGC2.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.