Narrative:

Prior to beginning descent into cali, we attempted twice to enter the arrival in the database for runway 5 at clo. Each time the PL1 line button was pushed, the sel annunciation would not appear and then the fmcs would annunciate synching and the autothrottles would disconnect, the autoplt disconnected once and when the first officer FMC was used to attempt the same thing, his FMC annunciated fail and we lost the autothrottles, all autoplt capability, and the vors, which were in the expanded mode at the time went dead and had failure flags. Since we were over a route fix at the time, I had the first officer reload all the FMC data, which had dumped, and I flew the approximately heading outbound until he had the fmcs reloaded. At that time the system restored to full capability and the course lines agreed with the raw data which I was then able to navigation on. No further failures were noted. After we shut down at the gate at clo, we re-tried the same entry in route #2 and it took it normally. This entire event had me looking over my shoulder at ctg which we had just passed and was clear. No further failures noted. Callback conversation with reporter revealed the following information: the captain said that they were just passing uib, he thinks, when the fmcs began to malfunction. The FMC were operating in route #1 at the time. Later, on the ground in clo the crew loaded the return information in route #2, route #1 dropped out of the computer once they had landed, as normal. They then attempted, unsuccessfully, to duplicate the failure. The crew also sent the failure information to their maintenance facility in the united states via ACARS. The maintenance facility had them do several checks of the fmcs, but no failures could be induced and the maintenance personnel via ACARS and in their home base cleared the aircraft for the return flight. After returning, the captain said that he was met with both maintenance and technical representatives from the manufacturer several times, but does not think that the source of the failure has been determined. The most disturbing aspect of the failure was that temporarily the crew lost both the fmcs and the raw data from the VOR receivers. Only by reloading the route data in the fmcs did they get their navigation capability to return. The reporter said that his company is quite concerned about this incident and he is thankful that it happened at FL330.

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Original NASA ASRS Text

Title: ACR B757-200ER FLC LOST THEIR FMCS, AUTOPLTS, AUTOTHROTTLES AND THE VOR RECEIVERS DURING CRUISE FLT IN FOREIGN AIRSPACE.

Narrative: PRIOR TO BEGINNING DSCNT INTO CALI, WE ATTEMPTED TWICE TO ENTER THE ARR IN THE DATABASE FOR RWY 5 AT CLO. EACH TIME THE PL1 LINE BUTTON WAS PUSHED, THE SEL ANNUNCIATION WOULD NOT APPEAR AND THEN THE FMCS WOULD ANNUNCIATE SYNCHING AND THE AUTOTHROTTLES WOULD DISCONNECT, THE AUTOPLT DISCONNECTED ONCE AND WHEN THE FO FMC WAS USED TO ATTEMPT THE SAME THING, HIS FMC ANNUNCIATED FAIL AND WE LOST THE AUTOTHROTTLES, ALL AUTOPLT CAPABILITY, AND THE VORS, WHICH WERE IN THE EXPANDED MODE AT THE TIME WENT DEAD AND HAD FAILURE FLAGS. SINCE WE WERE OVER A RTE FIX AT THE TIME, I HAD THE FO RELOAD ALL THE FMC DATA, WHICH HAD DUMPED, AND I FLEW THE APPROX HEADING OUTBOUND UNTIL HE HAD THE FMCS RELOADED. AT THAT TIME THE SYS RESTORED TO FULL CAPABILITY AND THE COURSE LINES AGREED WITH THE RAW DATA WHICH I WAS THEN ABLE TO NAV ON. NO FURTHER FAILURES WERE NOTED. AFTER WE SHUT DOWN AT THE GATE AT CLO, WE RE-TRIED THE SAME ENTRY IN RTE #2 AND IT TOOK IT NORMALLY. THIS ENTIRE EVENT HAD ME LOOKING OVER MY SHOULDER AT CTG WHICH WE HAD JUST PASSED AND WAS CLR. NO FURTHER FAILURES NOTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAPT SAID THAT THEY WERE JUST PASSING UIB, HE THINKS, WHEN THE FMCS BEGAN TO MALFUNCTION. THE FMC WERE OPERATING IN RTE #1 AT THE TIME. LATER, ON THE GND IN CLO THE CREW LOADED THE RETURN INFO IN RTE #2, RTE #1 DROPPED OUT OF THE COMPUTER ONCE THEY HAD LANDED, AS NORMAL. THEY THEN ATTEMPTED, UNSUCCESSFULLY, TO DUPLICATE THE FAILURE. THE CREW ALSO SENT THE FAILURE INFO TO THEIR MAINT FACILITY IN THE UNITED STATES VIA ACARS. THE MAINT FACILITY HAD THEM DO SEVERAL CHKS OF THE FMCS, BUT NO FAILURES COULD BE INDUCED AND THE MAINT PERSONNEL VIA ACARS AND IN THEIR HOME BASE CLRED THE ACFT FOR THE RETURN FLT. AFTER RETURNING, THE CAPT SAID THAT HE WAS MET WITH BOTH MAINT AND TECHNICAL REPRESENTATIVES FROM THE MANUFACTURER SEVERAL TIMES, BUT DOES NOT THINK THAT THE SOURCE OF THE FAILURE HAS BEEN DETERMINED. THE MOST DISTURBING ASPECT OF THE FAILURE WAS THAT TEMPORARILY THE CREW LOST BOTH THE FMCS AND THE RAW DATA FROM THE VOR RECEIVERS. ONLY BY RELOADING THE RTE DATA IN THE FMCS DID THEY GET THEIR NAV CAPABILITY TO RETURN. THE RPTR SAID THAT HIS COMPANY IS QUITE CONCERNED ABOUT THIS INCIDENT AND HE IS THANKFUL THAT IT HAPPENED AT FL330.

Data retrieved from NASA's ASRS site as of July 2007 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.