Narrative:

On preflight the first officer, so and I discussed the previous write ups in the maintenance logbook, especially the loss of #3 bus on takeoff on a previous flight. On takeoff on runway 24 the WX was VFR and the winds were 250 degree at 08 KTS. The first officer was flying. Just after liftoff, we experienced a #3 flight station bus failure, electrical differential fault which indicates a short circuit between the generator breaker and the AC tie bus. The first officer had basic instruments and continued flying. I conferred with so and we decided to return to manchester. I told the tower we had an electrical problem, needed to dump fuel and return for landing. Departure control vectored us to a fuel dumping area. We completed all the normal, abnormal checklists and dumped enough fuel for a landing weight of 418000 pounds. I decided to make the approach and landing. I had flight direction and the first officer did not. The WX continued to be VFR, with the wind 250 degree and 08 KTS. The visibility was 10 plus mi. The landing and taxi were uneventful. In review, I am glad we reviewed and discussed prior problem from the aircraft maintenance logbook, so we were not taken by surprise by the electrical failure. The next day the mechanic told us that there was a water leak in the business class lav, that leaks into the top of a cargo container and pooled and that probably on liftoff, this water drifted onto the #3 generator control unit, causing the electrical short.

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Original NASA ASRS Text

Title: A WDB ACR HAD TO DUMP FUEL, RETURN, AND LAND BECAUSE THEY LOST PART OF THEIR ELECTRICAL SYS ON TKOF.

Narrative: ON PREFLT THE FO, SO AND I DISCUSSED THE PREVIOUS WRITE UPS IN THE MAINT LOGBOOK, ESPECIALLY THE LOSS OF #3 BUS ON TKOF ON A PREVIOUS FLT. ON TKOF ON RWY 24 THE WX WAS VFR AND THE WINDS WERE 250 DEG AT 08 KTS. THE FO WAS FLYING. JUST AFTER LIFTOFF, WE EXPERIENCED A #3 FLT STATION BUS FAILURE, ELECTRICAL DIFFERENTIAL FAULT WHICH INDICATES A SHORT CIRCUIT BTWN THE GENERATOR BREAKER AND THE AC TIE BUS. THE FO HAD BASIC INSTS AND CONTINUED FLYING. I CONFERRED WITH SO AND WE DECIDED TO RETURN TO MANCHESTER. I TOLD THE TWR WE HAD AN ELECTRICAL PROBLEM, NEEDED TO DUMP FUEL AND RETURN FOR LNDG. DEP CTL VECTORED US TO A FUEL DUMPING AREA. WE COMPLETED ALL THE NORMAL, ABNORMAL CHKLISTS AND DUMPED ENOUGH FUEL FOR A LNDG WT OF 418000 POUNDS. I DECIDED TO MAKE THE APCH AND LNDG. I HAD FLT DIRECTION AND THE FO DID NOT. THE WX CONTINUED TO BE VFR, WITH THE WIND 250 DEG AND 08 KTS. THE VISIBILITY WAS 10 PLUS MI. THE LNDG AND TAXI WERE UNEVENTFUL. IN REVIEW, I AM GLAD WE REVIEWED AND DISCUSSED PRIOR PROBLEM FROM THE ACFT MAINT LOGBOOK, SO WE WERE NOT TAKEN BY SURPRISE BY THE ELECTRICAL FAILURE. THE NEXT DAY THE MECH TOLD US THAT THERE WAS A WATER LEAK IN THE BUSINESS CLASS LAV, THAT LEAKS INTO THE TOP OF A CARGO CONTAINER AND POOLED AND THAT PROBABLY ON LIFTOFF, THIS WATER DRIFTED ONTO THE #3 GENERATOR CTL UNIT, CAUSING THE ELECTRICAL SHORT.

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.