Narrative:

On departure from zspd; in a climb between approximately 6;000 feet and FL250 and in contact with shanghai departure control; we experienced the following event: both FMC's timed out and 'time-out-reselect' was shown in the scratch pad. In short order we then lost flight directors; autothrottle; LNAV/VNAV and autopilot as well as ACARS. EICAS messages did not indicate an FMC failure; but showed all the associated messages typical of an FMC failure. We attempted to reload the route; which failed; when both fmcs timed out again. This time all information was removed/dumped from the fmcs; including performance. All EICAS messages were advisory only and required no QRH procedure. The left radio also was unusable which created a delay in communicating with ATC; that radar vectors were required until we could re-establish navigation capability. This resulted in a lateral course deviation of approx. 5-7 miles. A second attempt to reload all performance and routing was successful and all systems were restored. Maintenance history revealed that approximately 15 days ago; the left FMC had failed in flight as was reported in the logbook. We then opted to select the right FMC as the master FMC for flight guidance; a/P and a/T for the rest of the flight. Shanghai control provided radar vectors until we restored navigation capability. We were then handed off to fukuoka control. The flight continued and landed ahead of schedule without further ado. If we had had a FMC fail EICAS message; we would have followed the procedure; which would have led us to select CDU center or right respectively and given us an nd depiction of the route to fly. Without EICAS FMC failure message; we were only concerned with flying the airplane and recovering our route and performance so as to return to normal navigation. This was not a 'normal' non-normal event that followed a linear course of action. It required intuitive input and creative responses to restore normal operations.

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Original NASA ASRS Text

Title: B747-400 Captain experiences a dual FMC failure shortly after takeoff although no EICAS annunciation of FMC failure was present. The first attempt to reload the FMC's is not successful and ATC is advised and vectors requested. The second attempt to restore the FMC's is successful and the flight continues to destination.

Narrative: On departure from ZSPD; in a climb between approximately 6;000 feet and FL250 and in contact with Shanghai Departure Control; we experienced the following event: Both FMC's timed out and 'time-out-reselect' was shown in the scratch pad. In short order we then lost flight directors; autothrottle; LNAV/VNAV and autopilot as well as ACARS. EICAS messages did not indicate an FMC failure; but showed all the associated messages typical of an FMC failure. We attempted to reload the route; which failed; when both FMCs timed out again. This time all information was removed/dumped from the FMCs; including performance. All EICAS messages were advisory only and required no QRH procedure. The left radio also was unusable which created a delay in communicating with ATC; that radar vectors were required until we could re-establish navigation capability. This resulted in a lateral course deviation of approx. 5-7 miles. A second attempt to reload all performance and routing was successful and all systems were restored. Maintenance history revealed that approximately 15 days ago; the L FMC had failed in flight as was reported in the logbook. We then opted to select the R FMC as the master FMC for flight guidance; A/P and A/T for the rest of the flight. Shanghai Control provided radar vectors until we restored navigation capability. We were then handed off to Fukuoka Control. The flight continued and landed ahead of schedule without further ado. If we had had a FMC FAIL EICAS message; we would have followed the procedure; which would have led us to select CDU Center or Right respectively and given us an ND depiction of the route to fly. Without EICAS FMC failure message; we were only concerned with flying the airplane and recovering our route and performance so as to return to normal navigation. This was not a 'normal' non-normal event that followed a linear course of action. It required intuitive input and creative responses to restore normal operations.

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.