S2/2007 Boeing 777-222, N786UA
S2/2007 Boeing 777-222, N786UA
Summary:
After engines start, about the time the engine driven Integrated Drive Generators (IDGs) would normally come on-line, the flight deck instrument displays flickered, the crew heard an abnormal noise and an EICAS message, amongst other related messages, indicated that the Right Main AC Bus had failed. Some 40 seconds after the engines had stabilised at ground idle, the smoke detector in the Main Equipment Centre (MEC), located beneath the flight deck and forward vestibule, detected smoke. About two and a half minutes after the electrical failure, the crew became aware of a faint smell of electrical burning on the flight deck, following which the right engine was shut down. The crew were alerted by the ground handling crew that smoke was seen to be coming from the MEC vent and, a couple of minutes later, ATC also advised that smoke had been seen coming from the aircraft. The aircraft was taxied to a nearby stand, where the left engine was shut down. Approximately twelve and a half minutes after the failure, the batteries were switched off and the passengers deplaned via steps. No fire was detected by the Airport Fire Service but, after the smoke had cleared in the MEC, obvious evidence of fire and electrical arcing damage was present within the P200 electrical power panel, and to the Right Generator Circuit Breaker and the Right Bus Tie Breaker in particular. It was also apparent that fire had been associated with the thermal/acoustic insulation blankets behind and beneath the P200 panel. The manufacturer has investigated 11 in-service reports of similar power panel events on B777 aircraft, and has published details of preventative action that operators may take. The Chief Inspector of Air Accidents has ordered an Inspector’s Investigation to be conducted into the circumstances of this accident.
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