A 2015 engine fire on a British Airways 777-236ER was
caused by a fatigue crack in the high-pressure compressor stage 8 disk web and
subsequent uncontained engine failure, which led to the detachment of the main
fuel supply line, the National
Transportation Safety Board found Wednesday.
The September 8, 2015 fire occurred during the takeoff
roll at McCarran International Airport in Las Vegas. Two seconds after hearing
a “bang,” the captain aborted the takeoff, and the jetliner came to a stop on
the runway 13 seconds later. The 157 passengers, including one lap child, and
13 crewmembers evacuated via emergency slides. The flight’s destination
was London-Gatwick Airport.
The captain ordered passengers to evacuate from the
right side of the airplane. But the NTSB found that the unaffected right engine
continued to run for 43 seconds after the captain’s order, resulting in jet
blast blowing two emergency slides out of position and rendering them unusable
for the evacuation. The passengers and crew were able to use two of the eight
doors to leave the airplane before smoke and fire encroached the fuselage.
The left engine of the 777-236ER after the fire.
The NTSB found that the captain did not use his quick
reference handbook to read and do checklist items. It was only when a third
pilot in the cockpit noticed instruments indicating the right engine was still
running that the engine was shut down. “Because the captain did not follow
standard procedures, his call for the evacuation checklist and the shutdown of
the right engine were delayed,” the report said.
The high-pressure compressor stage 8-10 spool in the
left engine, one of two GE GE90-85BG11 engines on the airplane, had accumulated
11,459 total cycles. Investigators found that the crack initiated after about
6,000 cycles, much earlier than the engine’s manufacturer, GE, predicted; the
cause of the crack initiation could not be identified. There were no additional
cracks found on the disk during a post-accident inspection of the engine.
The disk web was not an area that either the Federal
Aviation Administration or the manufacturer required to be inspected, so
the crack went undetected. During maintenance in September 2008, when the
high-pressure compressor was removed from the engine and disassembled, exposing
the stage 8-10 spool, the surface crack length would have been about 0.05
inches. “If the disk web had been required to be inspected during this
maintenance, the crack should have been detectable,” the report said. The lack
of inspection procedures for the stage 8 disk contributed to the accident, the
NTSB found. After the accident, GE implemented inspection procedures designed
to detect disk web cracks.
The full report can be found here
or on NTSB.gov.