8th of September 2015, Blog #531
With a crew of 13 and 157 passengers, a Boeing 777-236ER was taxing to 7L at Las Vegas, McCarran International Aiport (California, USA) for a scheduled passenger flight to London Heathrow Aiport (England), on this day in 2015. The captain was the pilot flying (PF) with the co-pilot operating as pilot monitoring (PF) for the flight, a relief pilot on the jumpseat on the flightdeck.
The left engine (© NTSB)
The weather was good this afternoon;
Clouds - Scattered
Temp. - 39 ºC
Dew Pt. - 5 ºC
Visibility - 10 miles
After the aircraft reached the runway the take-off clearance was issued and the PF advanced the throttles to the take-off detent, and the aircraft started its take-off roll at 16.12:42 lt (local time) with both GE90 engines accelerating to the take-off thrust setting. 9 seconds into the take-off roll a 'thud' and a 'bang' were heard. two seconds later the CVR picked up the sound of an engine spooling down. At the same time, an ENGINE FAIL warning was displayed on the EICAS (Engine Indicating and Crew Alerting System) and an aural warning "ENGINE FAIL" was given. The aircraft yawed to the left as the PF called out "STOP", and pulled the throttles to idle. The speed at the time was 77 knots (Well below the take-off decision speed for the flight, which was 149 knots. During the aborted off the left engine fire warning sounded for 1.8 seconds.
The damaged right-hand fuselage (© NTSB)
At 16.12:58 the PM alerted ATC at the captain's request while the relief pilot made an announcement to the cabin crew and passengers to remain seated and await further instructions.
1 second later the captain also contacted ATC declaring MAYDAY and requesting the fire department, which ATC confirmed. In the meantime, the first officer had started the memories items from the engine fire checklist by moving the left fuel control switch to the cutoff position. Which he followed up by pulling and then rotating the left engine fire switch to discharge the first fire extinguisher bottle into the left engine, after thirty seconds, the second fire extinguisher bottle was discharged. A short moment later the fire warning extinguished. The relief pilot went to the cabin to check the situation on the engine and observed black smoke and an orange glow outside the aircraft. Before returning to the flight deck he told a cabin crew member to get ready for an evacuation. After returning to the flightdeck the relief pilot informed the captain about his observations.
NTSB investigators collecting evidence under the severely damaged aircraft (source; cdn.images.express.co.uk © Unknown)
At 16.14:23 the captain initiated an emergency evacuation by making the following announcement; "THIS IS AN EMERGENCY, THIS THE CAPTAIN. EVACUATE. EVACUATE.", just under 32 seconds had passed since the bang was heard. The PM informed ATC they were evacuating on the runway due to a fire. The right-hand engine was shut down and the Evacuation Checklist from the QRH was performed. Firefighters arrived at the aircraft less than 2 minutes after the captain's request, 2 minutes and 26 seconds later the fire was extinguished. All crew and passengers evacuated the aircraft in 2 minutes and 32 seconds after the captains' evacuation command. !9 passengers sustained minor injuries, and 1 cabin attendant received serious injuries during the evacuation.
The National Transportation Safety Board (NTSB) was alerted and an investigation was started. Initial evaluation of the aircraft revealed serious (fire) damage to the aircraft due to an uncontained failure of the left-hand engine. In their report the NTSB identifies the following probable cause for the engine failure;
"The failure of the left engine high-pressure compressor (HPC) stage 8-10 spool, which caused the main fuel supply line to become detached from the engine main fuel pump and release fuel, resulting in a fire on the left side of the airplane. The HPC stage 8-10 spool failed due to a sustained-peak low-cycle fatigue crack that initiated in the web of the stage 8 disk; the cause of the crack initiation could not be identified by physical inspection and stress and lifetime analysis."
Contributing to this accident was the lack of inspection procedures for the stage 8 disk web.
GE90 engine cross-section with the locations of the HPC stage 8-10 spool separation and stage 8 disk separation. (Source; GE)
The aircraft underwent major repairs and was returned to service. The NTSB investigation report, on which this blog is based, is available for the readers reference (providing full details of the events and investigation) by clicking on the .pdf file below;
The aircraft departed Las Vegas on the 26th of February 2016 after completion of the repairs (© Barry Ambrose)