Narrative:When climbing through FL380, en route to Kuala Lumpur, the crew reported that they observed a low airspeed warning on the aircraft’s EICAS. Then the crew got instrument indications 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 captain disconnected the autopilot and lowered the nose of the aircraft. The autothrottle commanded an increase in thrust which the captain countered by manually moving the thrust levers to the idle position. The aircraft pitched up again and climbed 2,000 ft. The captain notified air traffic control (ATC) that they could not maintain altitude and requested a descent and radar assistance. The crew was able to verify with ATC the aircraft speed and altitude. Both left and right autopilots caused the aircraft to bank and the nose to pitch down, so the captain decided to fly the aircraft manually. The flight made an ILS approach to Perth's runway 03. The wind at Perth was gusting from the north-west with moderate turbulence below 3,000 ft. During the approach, the aircraft warning system indicated a windshear condition but the crew continued the approach and landed the aircraft without further incident.
CONTRIBUTING SAFETY FACTORS: "An anomaly existed in the component software hierarchy that allowed inputs from a known faulty accelerometer to be processed by the air data inertial reference unit (ADIRU) and used by the primary flight computer, autopilot and other aircraft systems.
OTHER SAFETY FACTORS:
- The software anomaly was not detected in the original testing and certification of the ADIRU.
- The aircraft documentation did not provide the flight crew with specific information and action items to assess and respond to the aircraft upset event."
Official accident investigation report
|investigating agency: ||Australian Transport Safety Bureau (ATSB) - Australia |
|report status: ||Final|
|report number: ||ATSB Occurrence 200503722|
|duration of investigation:||589 days (1 year 7.5 months)|
|download report: ||
In-flight upset; 240km NW Perth, WA; Boeing Co 777-200, 9M-MRG
(ATSB Occurrence 200503722)
Follow-up / safety actions
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not
display the exact flight path.
Distance from Perth Airport, WA to Kuala Lumpur International Airport as the crow flies is 4128 km (2580 miles).