Narrative:

During cruise, an electronic dc bus failed in the #2 system indicated by 1 full page of EICAS messages and 2 full pages of status messages. After about 45 mins of troubleshooting (unsuccessfully), the flight diverted to akl. No bus was indicated on the EICAS system and no primary system were included in the messages -- specifically, the antiskid, autobrake, autospoiler, and engine reverse system were not included. All 4 failed to work on landing. This is not a bus I want to lose! Brakes were applied and manual spoilers were extended. One tire blew during rollout. The brake temperatures ranged from zero to a maximum of 7 (amber) after landing, suggesting very uneven braking applications. (Satcom was very erratic and intermittent.) they were unable to download via ACARS/satcom and did not identify our problem. Red label this bus and warn future crews if it fails. Train that manual braking will cause 1 or more blown tires since the brake system is poorly designed. We did not need any assistance (this time). Perhaps we can develop a method that is not monitored. Why are so many unannounced items on 1 bus? Ask boeing. Supply a headset that transmits from the electronics bay. We dumped (115000 pounds) fuel at FL350 prior to 60 mins from landing. Our gross weight was +/-625.0 pounds. The landing was smooth, so there was lots of tire smoke -- a firmer landing would create less. The flight attendants were alerted, the cabin was not prepped. Callback conversation with reporter revealed the following information: the reporter stated the failure of the #2 dc bus was caused by a feed wire lug burned and broken. The reporter said the dead #2 dc bus failed the engine reversing, antiskid, engine #3 eec, and autospoiler system. The reporter said the satcom system was erratic and maintenance was unable to download and identify their problem. The reporter stated the flight diverted to akl and blew a tire on landing.

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Original NASA ASRS Text

Title: A B747-400 IN CRUISE AT FL350 DECLARED AN EMER AND DIVERTED DUE TO #2 DC BUS FAILURE CAUSED BY A BROKEN AND BURNED BUS SUPPLY WIRE LUG.

Narrative: DURING CRUISE, AN ELECTRONIC DC BUS FAILED IN THE #2 SYS INDICATED BY 1 FULL PAGE OF EICAS MESSAGES AND 2 FULL PAGES OF STATUS MESSAGES. AFTER ABOUT 45 MINS OF TROUBLESHOOTING (UNSUCCESSFULLY), THE FLT DIVERTED TO AKL. NO BUS WAS INDICATED ON THE EICAS SYS AND NO PRIMARY SYS WERE INCLUDED IN THE MESSAGES -- SPECIFICALLY, THE ANTISKID, AUTOBRAKE, AUTOSPOILER, AND ENG REVERSE SYS WERE NOT INCLUDED. ALL 4 FAILED TO WORK ON LNDG. THIS IS NOT A BUS I WANT TO LOSE! BRAKES WERE APPLIED AND MANUAL SPOILERS WERE EXTENDED. ONE TIRE BLEW DURING ROLLOUT. THE BRAKE TEMPS RANGED FROM ZERO TO A MAX OF 7 (AMBER) AFTER LNDG, SUGGESTING VERY UNEVEN BRAKING APPLICATIONS. (SATCOM WAS VERY ERRATIC AND INTERMITTENT.) THEY WERE UNABLE TO DOWNLOAD VIA ACARS/SATCOM AND DID NOT IDENT OUR PROB. RED LABEL THIS BUS AND WARN FUTURE CREWS IF IT FAILS. TRAIN THAT MANUAL BRAKING WILL CAUSE 1 OR MORE BLOWN TIRES SINCE THE BRAKE SYS IS POORLY DESIGNED. WE DID NOT NEED ANY ASSISTANCE (THIS TIME). PERHAPS WE CAN DEVELOP A METHOD THAT IS NOT MONITORED. WHY ARE SO MANY UNANNOUNCED ITEMS ON 1 BUS? ASK BOEING. SUPPLY A HEADSET THAT XMITS FROM THE ELECTRONICS BAY. WE DUMPED (115000 LBS) FUEL AT FL350 PRIOR TO 60 MINS FROM LNDG. OUR GROSS WT WAS +/-625.0 LBS. THE LNDG WAS SMOOTH, SO THERE WAS LOTS OF TIRE SMOKE -- A FIRMER LNDG WOULD CREATE LESS. THE FLT ATTENDANTS WERE ALERTED, THE CABIN WAS NOT PREPPED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE FAILURE OF THE #2 DC BUS WAS CAUSED BY A FEED WIRE LUG BURNED AND BROKEN. THE RPTR SAID THE DEAD #2 DC BUS FAILED THE ENG REVERSING, ANTISKID, ENG #3 EEC, AND AUTOSPOILER SYS. THE RPTR SAID THE SATCOM SYS WAS ERRATIC AND MAINT WAS UNABLE TO DOWNLOAD AND IDENT THEIR PROB. THE RPTR STATED THE FLT DIVERTED TO AKL AND BLEW A TIRE ON LNDG.

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.