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B747 flight crew reported a possible dual FMS failure during climb that resulted in a course deviation.
| Attributes | |
| ACN | 1707658 |
| Time | |
| Date | 201912 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Aircraft 1 | |
| Make Model Name | B747-400 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Climb |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | FMS/FMC |
| Person 1 | |
| Function | Captain |
| Qualification | Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical |
Narrative:
Shortly after departure from ZZZ we were given radar vectors for the climb after we notified ATC that we were unable to make the next altitude at the next fix on the departure.about five minutes into the climb there was a scratch-pad message re-syncing other FMC (flight management computer) followed by timeout reselect; autothrottle disconnect and EICAS message and autopilot disconnect and EICAS message.after reselecting FMC everything appeared normal and I reselected the autopilot and connected the auto throttle and reengaged VNAV (vertical navigation).shortly thereafter same happened again with the loss of all initial information in the CDU (control display unit) and no waypoints in either route 1 or 2 and a magenta line through VNAV mode annunciation. The first officer (first officer) notified ATC that we were working a 'problem' and received further climb and heading instructions. The first officer loaded all the information back into the CDU and I reengaged the automation. Received a direct to a fix on our route from ATC and continued the rest of the flight without further incident.I think we had a dual FMC failure where the left one recovered fast enough to not trigger an FMC EICAS message.
Original NASA ASRS Text
Title: B747 flight crew reported a possible dual FMS failure during climb that resulted in a course deviation.
Narrative: Shortly after departure from ZZZ we were given radar vectors for the climb after we notified ATC that we were unable to make the next altitude at the next fix on the departure.About five minutes into the climb there was a scratch-pad message re-syncing other FMC (Flight Management Computer) followed by timeout reselect; autothrottle disconnect and EICAS message and autopilot disconnect and EICAS message.After reselecting FMC everything appeared normal and I reselected the Autopilot and connected the auto throttle and reengaged VNAV (Vertical Navigation).Shortly thereafter same happened again with the loss of all initial information in the CDU (Control Display Unit) and no waypoints in either route 1 or 2 and a magenta line through VNAV mode annunciation. The FO (First Officer) notified ATC that we were working a 'problem' and received further climb and heading instructions. The FO loaded all the information back into the CDU and I reengaged the automation. Received a direct to a fix on our route from ATC and continued the rest of the flight without further incident.I think we had a dual FMC failure where the left one recovered fast enough to not trigger an FMC EICAS message.
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.