GE Aviation was unable to identify the cause of a disk web crack that caused a GE90-powered British Airways 777-200 to fail during a takeoff roll on a Las Vegas airport runway nearly three years ago, the US National Transportation Safety Board (NTSB) says.
Although the NTSB’s 33-month investigation did not identify a root cause for the engine failure, the board’s investigators raised questions about the checklist and steps taken by the crew that may have delayed the evacuation and worsened the fire on the runway.
One crew member suffered a serious injury and 19 passengers reported minor injuries during the 9 September 2015 incident, which involved British Airways flight 66 from Las Vegas to London.
The disk web stage 8-10 inside the high pressure compressor exploded as the aircraft accelerated to take-off. The crew commanded a rejected takeoff procedure within 2s of the engine failure, causing the aircraft to slow to a stop from 77kt within 13s.
An extensive metallurgical examination of the failed component revealed evidence of a sustained-peak low-cycle fatigue crack in the stage 8-10 disk web, but could not determine a root cause, the NTSB says.
The first signs of the crack should have been detectable during a maintenance check in 2008, but there was no requirement to inspect the disk web, the NTSB says. GE now has procedures to check for disk web cracks during routine maintenance, the agency adds.
Boeing told the NTSB that an estimated 436l (97gal) of jet fuel spilled onto the runway at Las Vegas McCarran International Airport. The spill occurred during the 28s between the engine failure and the moment that the crew shut off the fuel valve to the engine, the NTSB says.
The captain called for the engine fire checklist twice before starting the procedure, according to the NTSB’s review of the cockpit voice recorder. About 13s elapsed between the captain’s second call for the checklist and the closure of the fuel valve.
“British Airways' engine fire checklist, which was based on the Boeing 777 engine fire checklist, did not differentiate between an engine fire occurring on the ground or during flight,” the NTSB says.
“The third step of the checklist instructed the flight crew to cut off the fuel control switch on the affected side to shut down that engine,” the agency adds. “However, for an engine fire on the ground, the checklist did not include a step to shut down the unaffected engine or indicate that some steps did not apply.”
Source: Cirium Dashboard