At their request, the National Transportation Safety Board is
assisting in the dissemination of the AAIB report, which
Accident to a Boeing 777-236, G-YMMM, on 17 January 2008
at 1243 hrs
Initial Report Update 23 January 2008
Since the issue of the Air Accidents Investigation Branch (AAIB)
1st Preliminary Report on
Friday 18th January 2008 at 1700 hrs, work has continued on all
fronts to identify why neither engine responded to throttle lever
inputs during the final approach. The 150 tonne aircraft was
moved from the threshold of Runway 27L to an airport apron on
Sunday evening, allowing the airport to return to normal
The AAIB, sensitive to the needs of the industry including Boeing,
Rolls Royce, British Airways and other Boeing 777 operators and
crews, is issuing this update to provide such further factual
information as is now available.
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.
Recorded data indicates that an adequate fuel quantity was on
board the aircraft and that the autothrottle and engine control
commands were performing as expected prior to, and after, the
reduction in thrust.
All possible scenarios that could explain the thrust reduction
and continued lack of response of the engines to throttle lever
inputs are being examined, in close cooperation with Boeing, Rolls
Royce and British Airways. This work includes a detailed analysis
and examination of the complete fuel flow path from the aircraft
tanks to the engine fuel nozzles.
Further factual information will be released as and when