An uncontained engine failure has emerged as a possible source of the fire that damaged a British Airways Boeing 777-200ER on a Las Vegas runway on 8 September.
Preliminary findings released by the US National Transportation Safety Board on 10 September indicated multiple breaches of the engine fan case in the region of the high-pressure compressor.
Several pieces of about 17.8-20.3cm (7-8in) in length from the high-pressure compressor spool were found on the runway, the NTSB says.
What caused pieces to separate from the spool has not been identified.
The 777, powered by two GE90-85B engines, had started a take-off roll shortly after 16:00 from Las Vegas McCarran airport, bound for London Gatwick airport with 157 passengers and 13 crew members.
The pilot reportedly became aware of a "catastrophic" engine failure and aborted the take-off from runway 7L. With local meteorology data indicating an 8kt crosswind at the time of the incident, a fire spread inboard from the damaged left engine along the wing and side of the fuselage. The passengers and crew evacuated via emergency slides onto the runway, while airport fire crews doused the flames within 5min of the initial report.
The NTSB has now recovered the flight data recorder, cockpit voice recorder and quick-access recorder, which are being downloaded as of this afternoon.
The circumstances continue to resemble more closely the 1985 fire that killed 55 passengers aboard a British AirTours 737-200. In that example, the flight crew aborted a take-off after an uncontained engine failure had punctured a wing fuel tank, while a crosswind pushed the fire inboard to ignite the passenger cabin through an opened aft emergency door.
The GE90 has an impressive in-flight shutdown rate of 0.001, or one per one million hours, over a nearly 20-year service history, but it has not been immune from contained failures in the high-pressure compressor.
In 2011, the US Federal Aviation Administration issued an airworthiness directive on a larger version of the same engine core. Pieces of seal teeth from the compressor's first and second stages exploded within the engine. The failure was traced to "heavy rubs" by the seal teeth and the FAA mandated that operators perform eddy current inspection to identify telltale signs of cracking that could lead to uncontained failures.
The FAA issued a similar directive in 1998 for the same seal teeth cracking issue of the compressor for the GE90-85, the same version of the engine on the 777 in Las Vegas.
This article has been updated to clarify the in-flight shutdown rate
Source: Cirium Dashboard