A B777-200 generator did not come on line after a delayed takeoff start. Upon return to the gate for...

Attributes
ACN	812050
Time
Date	200811
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B777-200
Operating Under FAR Part	Part 121
Flight Phase	ground : taxi
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 210 flight time total : 21000
ASRS Report	812050
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : multi engine pilot : flight engineer pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 15000 flight time type : 400
ASRS Report	812824
Events
Anomaly	aircraft equipment problem : less severe maintenance problem : non compliance with mel maintenance problem : improper documentation non adherence : far
Independent Detector	aircraft equipment other aircraft equipment : eicas other flight crewa other flight crewb
Resolutory Action	none taken : detected after the fact
Consequence	other
Supplementary
Problem Areas	Maintenance Human Performance Aircraft Flight Crew Human Performance
Primary Problem	Maintenance Human Performance

Narrative:

Our flight taxied out for takeoff to runway 14L. After waiting for an extensive period of time; the decision was made to start the APU and shut down the left engine. Shortly after that; we were informed to start all engines for takeoff. Upon restart; we noted a left generator controller off light illuminated; with no corresponding EICAS message. A reset was attempted with no resulting help. A shutdown and restart of the left engine was also attempted. This did not extinguish the light. We taxied back to the gate for fuel and maintenance. Maintenance signed off the logbook under MEL item #24-8 with no restrs indicated in the action to be taken column. After takeoff; noted that the electrical synoptic indicated the left generator did not appear to be pwring the busses. Again; there was no corresponding EICAS message associated with this condition. Contacted dispatch and with a phone patch to maintenance and at their direction; the left bus tie was opened and it was established that the loss of left main AC bus had occurred. With the fuel on board; dispatch released the aircraft airborne to ZZZ with the APU running en route. An additional burn of 3000 pounds of gas was calculated by dispatch. Dispatch and maintenance informed us that ZZZ maintenance would be informed. Inadvertently; no logbook entry was made. Supplemental information from acn 812824: I think our mechanics looked at our problem when we returned to the gate and signed off a problem and placarded a problem that we didn't have. Not knowing; or being required to know; more about the maintenance functions of our electrical system; left us in a poor position to troubleshoot the problem and allowed us to have something signed off that we didn't understand. It was a safe flight as the B777 has multiple electric sources and the MEL allows for several failures to dispatch safely.

Original NASA ASRS Text

Title: A B777-200 GENERATOR DID NOT COME ON LINE AFTER A DELAYED TAKEOFF START. UPON RETURN TO THE GATE FOR MAINTENANCE; AN INCORRECT MEL SIGN OFF ALLOWED DISPATCH. IN FLIGHT THE CREW DISCOVERED THE MAINTENANCE SIGN OFF ERROR.

Narrative: OUR FLT TAXIED OUT FOR TKOF TO RWY 14L. AFTER WAITING FOR AN EXTENSIVE PERIOD OF TIME; THE DECISION WAS MADE TO START THE APU AND SHUT DOWN THE L ENG. SHORTLY AFTER THAT; WE WERE INFORMED TO START ALL ENGS FOR TKOF. UPON RESTART; WE NOTED A L GENERATOR CONTROLLER OFF LIGHT ILLUMINATED; WITH NO CORRESPONDING EICAS MESSAGE. A RESET WAS ATTEMPTED WITH NO RESULTING HELP. A SHUTDOWN AND RESTART OF THE L ENG WAS ALSO ATTEMPTED. THIS DID NOT EXTINGUISH THE LIGHT. WE TAXIED BACK TO THE GATE FOR FUEL AND MAINT. MAINT SIGNED OFF THE LOGBOOK UNDER MEL ITEM #24-8 WITH NO RESTRS INDICATED IN THE ACTION TO BE TAKEN COLUMN. AFTER TKOF; NOTED THAT THE ELECTRICAL SYNOPTIC INDICATED THE L GENERATOR DID NOT APPEAR TO BE PWRING THE BUSSES. AGAIN; THERE WAS NO CORRESPONDING EICAS MESSAGE ASSOCIATED WITH THIS CONDITION. CONTACTED DISPATCH AND WITH A PHONE PATCH TO MAINT AND AT THEIR DIRECTION; THE L BUS TIE WAS OPENED AND IT WAS ESTABLISHED THAT THE LOSS OF L MAIN AC BUS HAD OCCURRED. WITH THE FUEL ON BOARD; DISPATCH RELEASED THE ACFT AIRBORNE TO ZZZ WITH THE APU RUNNING ENRTE. AN ADDITIONAL BURN OF 3000 LBS OF GAS WAS CALCULATED BY DISPATCH. DISPATCH AND MAINT INFORMED US THAT ZZZ MAINT WOULD BE INFORMED. INADVERTENTLY; NO LOGBOOK ENTRY WAS MADE. SUPPLEMENTAL INFO FROM ACN 812824: I THINK OUR MECHS LOOKED AT OUR PROB WHEN WE RETURNED TO THE GATE AND SIGNED OFF A PROB AND PLACARDED A PROB THAT WE DIDN'T HAVE. NOT KNOWING; OR BEING REQUIRED TO KNOW; MORE ABOUT THE MAINT FUNCTIONS OF OUR ELECTRICAL SYSTEM; LEFT US IN A POOR POSITION TO TROUBLESHOOT THE PROB AND ALLOWED US TO HAVE SOMETHING SIGNED OFF THAT WE DIDN'T UNDERSTAND. IT WAS A SAFE FLT AS THE B777 HAS MULTIPLE ELECTRIC SOURCES AND THE MEL ALLOWS FOR SEVERAL FAILURES TO DISPATCH SAFELY.

Data retrieved from NASA's ASRS site as of May 2009 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.

A B777-200 generator did not come on line after a delayed takeoff start. Upon return to the gate for maintenance; an incorrect MEL sign off allowed dispatch. In flight the crew discovered the maintenance sign off error.