At approximately 1703 Western Standard Time, on 1 August 2005, a Boeing Company 777-200 aircraft, (B777) registered 9M-MRG, was being operated on a scheduled international passenger service from Perth to Kuala Lumpur, Malaysia. The crew reported that, during climb out, they observed a LOW AIRSPEED advisory on the aircraft’s Engine Indication and Crew Alerting System (EICAS), when climbing through flight level (FL) 380. At the same time, the aircraft’s slip/skid indication deflected to the full right position on the Primary Flight Display (PFD). The PFD airspeed display then indicated that the aircraft was approaching the overspeed limit and the stall speed limit simultaneously. The aircraft pitched up and climbed to approximately FL410 and the indicated airspeed decreased from 270 kts to 158 kts. The stall warning and stick shaker devices also activated. The aircraft returned to Perth where an uneventful landing was completed.
The aircraft’s flight data recorder (FDR), cockpit voice recorder and the air data inertial reference unit (ADIRU) were removed for examination. The FDR data indicated that, at the time of the occurrence, unusual acceleration values were recorded in all three planes of movement. The acceleration values were provided by the aircraft’s ADIRU to the aircraft’s primary flight computer, autopilot and other aircraft systems during manual and automatic flight.
Subsequent examination of the ADIRU revealed that one of several accelerometers had failed at the time of the occurrence, and that another accelerometer had failed in June 2001.
Graphical and animated representation of flight data
Various representations of key parameters were prepared from the 9M-MRG downloaded flight data to assist in the analysis.
Graphical representation of relevant recorded data
General parameters over a 60-minute period containing the entire incident flight are displayed, see figure 6. Other relevant parameters are displayed over a 5-minute period incorporating the upset event, see figures 7-10.
Animated representation of relevant recorded data
An animation of the incident was prepared using Insight Animation™ software and is part of this report. A file containing the animation in Insight View™ format (.isv) is available for download from the ATSB website. This file requires the installation of an Insight Viewer that can be downloaded from www.flightscape.com at no charge. A still screen capture of the animation is shown at figure 11.
Download animated representation of flight data [4.4Mb.zip] please see the information above regarding the playing of this file.
|Date:||01 August 2005||Investigation status:||Completed|
|Time:||1703 hours WST|
|Location:||36 km S DONGA, (IFR)||Investigation type:||Occurrence Investigation|
|State:||Western Australia||Occurrence type:||Control - Other|
|Release date:||13 March 2007||Occurrence class:||Operational|
|Report status:||Final||Occurrence category:||Serious Incident|
|Highest injury level:||None|
|Aircraft manufacturer||The Boeing Company|
|Type of operation||Air Transport High Capacity|
|Damage to aircraft||Nil|
|Departure point||Perth, WA|
|Departure time||1625 hours WST|
|Destination||Kuala Lumpur, Malaysia|