The AAIB has released a further update on their investigation into the cause of Boeing 777 crash at London Heathrow.

Boeing 777-236 G-YMMM of the British Airways fleet crashed with no loss of life 300m short of the threshold of 27L at Heathrow on the 17th of January.

In the preliminary report it was established that neither engine responded to either autothrottle commands or manual throttle inputs during the last 40 or so seconds of flight.

The investigation has now revealed that the engines initially responded and then became asymmetric before both engines dropped to a power setting above flight-idle but below the requested setting.

From the report update:

As previously reported, whilst the aircraft was stabilised on an ILS approach with the autopilot engaged, the autothrust system commanded an increase in thrust from both engines. The engines both initially responded but after about 3 seconds the thrust of the right engine reduced. Some eight seconds later the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.

The full text of the update is available HERE

The AAIB will continue to investigate the accident and while a full report may be many months or even more than a year away, they will undoubtedly update manufacturers and operators of the 777 if they find any critical flaw in the design of the aircraft or systems.

Photo Credit: Adrian Pingstone

In a preliminary report from the AAIB on Thursday’s Boeing 777 crash at London Heathrow (British Airways Flight BA38) in which all 136 passengers and 16 crew survived, it is suggested that ‘unresponsive’ engines are at fault after brief Flight Data Recorder analysis.

In an earlier press conference held at British Airways headquarters, it was stated by Capt. Peter Burkill that his first-officer, John Coward was the handling pilot at the time of the crash.

Following an uneventful flight from Beijing, China, the aircraft was established on an ILS approach to Runway 27L at London Heathrow. Initially the approach progressed normally, with the Autopilot and Autothrottle engaged, until the aircraft was at a height of approximately 600 ft and 2 miles from touch down. The aircraft then descended rapidly and struck the ground, some 1,000 ft short of the paved runway surface, just inside the airfield boundary fence. The aircraft stopped on the very beginning of the paved surface of Runway 27L. During the short ground roll the right main landing gear separated from the wing and the left main landing gear was pushed up through the wing root. A significant amount of fuel leaked from the aircraft but there was no fire. An emergency evacuation via the slides was supervised by the cabin crew and all occupants left the aircraft, some receiving minor injuries.

At 600 feet, two miles out from 27 left on the extended centre-line, the autothrottles commanded increased power but the engines did not respond. The flight crew then moved the throttles manually with the same result. This situation is reported to have continued until the aircraft touched down about 300m from the threshold.

Initial indications from the interviews and Flight Recorder analyses show the flight and approach to have progressed normally until the aircraft was established on late finals for Runway 27L. At approximately 600 ft and 2 miles from touch down, the Autothrottle demanded an increase in thrust from the two engines but the engines did not respond. Following further demands for increased thrust from the Autothrottle, and subsequently the flight crew moving the throttle levers, the engines similarly failed to respond. The aircraft speed reduced and the aircraft descended onto the grass short of the paved runway surface.

As yet there is no word on the reason for the APU door being open as observed. All such information about the aircraft state on landing will probably come in the formal report.

As stated in the short preliminary report, the investigation into the crash of G-YMMM will continue until it’s culmination in a full formal report at some point in the future. There may be another ’special’ report a month or so from now.

Full Text Initial Report AAIB Ref: EW/C2008/01/01

Photo Credit: Marc-Antony Payne cc-by-3.0

Read on for the full text of the original initial report:

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