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B737-800 pilot reported a loss of FMC guidance on approach.
| Attributes | |
| ACN | 1518791 |
| Time | |
| Date | 201802 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Route In Use | Visual Approach |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | FMS/FMC |
| Person 1 | |
| Function | Pilot Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Overshoot Deviation - Procedural Clearance |
Narrative:
While flying the RNAV visual to runway xx we had a complete FMC failure while turning final to include loss of reference speed. I had not picked up the PAPI so I executed a go-around. We were given a heading of 190 and climb to 7;000 ft. We cleaned up on schedule and requested vectors to the ILS runway yy. As I was climbing through 6;000 ft ATC gave us a new level off altitude of 6;300 ft. I flew through 6;300 ft to approximately 6;500 ft at which time I returned back to 6;300 ft. He vectored us around to the runway yy ILS and we landed. Earlier in the flight we lost our FMC temporarily but route 1 had dumped. I had done a route copy so when the FMC came back we selected route 2. We verified the FMC was operating correctly so we continued to our destination. Both VNAV and LNAV were working properly the entire flight until final when all guidance was lost. I don't think this event could have been avoided due to it being an equipment failure. It was night time we were turning final on a very tight visual with no vertical or lateral guidance. The vref had disappeared even though we were at vref speed I felt it wouldn't be safe to continue the visual approach not knowing what other systems might be inoperative so I executed a go around in VMC conditions.
Original NASA ASRS Text
Title: B737-800 pilot reported a loss of FMC guidance on approach.
Narrative: While flying the RNAV Visual to Runway XX we had a complete FMC failure while turning final to include loss of reference speed. I had not picked up the PAPI so I executed a go-around. We were given a heading of 190 and climb to 7;000 ft. We cleaned up on schedule and requested vectors to the ILS Runway YY. As I was climbing through 6;000 ft ATC gave us a new level off altitude of 6;300 ft. I flew through 6;300 ft to approximately 6;500 ft at which time I returned back to 6;300 ft. He vectored us around to the Runway YY ILS and we landed. Earlier in the flight we lost our FMC temporarily but route 1 had dumped. I had done a route copy so when the FMC came back we selected Route 2. We verified the FMC was operating correctly so we continued to our destination. Both VNAV and LNAV were working properly the entire flight until final when all guidance was lost. I don't think this event could have been avoided due to it being an equipment failure. It was night time we were turning final on a very tight visual with no vertical or lateral guidance. The VREF had disappeared even though we were at VREF speed I felt it wouldn't be safe to continue the visual approach not knowing what other systems might be inoperative so I executed a go around in VMC conditions.
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.