NTSB, AAIB Investigate Another 777 Engine Power Loss
The NTSB has initiated an investigation involving a Boeing 777 that experienced an uncommanded engine power rollback late this fall and its potential ties to a dual engine rollback that led to the crash landing of a British Airways 777 shy of the runway at Heathrow last winter. The Air Accidents Investigation Board investigating that Jan. 17 nonfatal crash of a Boeing 777-236ER out of Beijing that crashed short of the runway at Heathrow released an interim report last September that detailed two likely causal scenarios. Both involved ice accretion in the fuel system. The Nov. 26, 2008, incident that has now won attention from the NTSB involves a similar Boeing 777 running similar Rolls-Royce Trent 895 engines, this time carrying 232 passengers out of Shanghai for Atlanta. The recent event began at 39,000 feet in the vicinity of Great Falls, Mont., on a 777-200ER operated by Delta as Flight 18. The Delta crew met the uncommanded rollback of the number-two engine with a procedural descent to 31,000 feet after which the engine recovered and behaved normally. The aircraft continued on its intended route and landed without incident. Investigative teams of both events are sharing personnel from both the AAIB and the NTSB to determine if the incidents share common issues.
The AAIB had written of the Heathrow accident that the accident aircraft had been exposed to both low fuel flows and temperatures as that aircraft had flown its descent. Circumstances surrounding the Delta flight may have been at least partially different. Flight data recorders have been retrieved from the Delta flight and both pilots have been interviewed. Final conclusions regarding the Heathrow crash have not yet been reached, but the accident led to new procedures for pilots that include varying altitude en route when fuel in the main tank falls below 10 degrees for more than three hours.