MH124 PER-KUL Returns to PER

[H Azmal 0]

http://www.atsb.gov.au/aviation/occurs/occ...?ID=767#factual

 

At approximately 1703 Western Standard Time, on 1 August 2005, a Boeing Company 777-200 aircraft, registered 9M-MRG, was being operated on a scheduled passenger service from Perth to Kuala Lumpur, Malaysia. The crew reported that they observed a low airspeed warning on the aircraft’s Engine Indication and Crew Alerting System 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 speed tape 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 pilot in command (PIC) disconnected the autopilot and lowered the nose of the aircraft. The autothrottle commanded an increase in thrust which the PIC countered by manually moving the thrust levers to the idle position. The aircraft pitched up again and climbed 2,000 ft. The PIC 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.

 

The PIC reported that the PFD indications appeared normal when descending through FL200. He selected the left autopilot on but the aircraft banked to the right and the nose pitched down so the autopilot was turned off. A similar situation occurred when the right autopilot was selected so the PIC manually flew the aircraft. There were no control difficulties experienced when the aircraft was flown manually, but the autothrottle `arm’ switches remained in the `armed’ position.

 

The crew was given radar vectors by ATC to position for an instrument landing system approach onto runway 03 at Perth. When the aircraft was at an altitude of 3,000 ft, and the crew was preparing for the approach, the PFD again indicated a low airspeed condition. The autothrottle system responded to the low airspeed condition by commanding an increase in thrust.

 

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.

 

The aircraft’s flight data recorder (FDR), cockpit voice recorder and the air data inertial reference unit (ADIRU) were removed for examination and analysis. The ADIRU was sent to the component manufacturer for examination under the supervision of the United States National Transportation Safety Board.

 

The FDR data indicated that, at the time of the occurrence, unusual and instantaneous acceleration values were recorded in all three planes of movement. The acceleration values were provided by the aircraft’s ADIRU and were used by the aircraft’s primary flight computer (PFC) during manual and automatic flight. The PFC compared the information from the ADIRU with the information from the Standby Air Data and Attitude Reference Unit (SAARU). During the occurrence, this comparison function reduced the severity of the initial pitching motion of the aircraft.

 

As a result of the occurrence, the aircraft manufacturer issued a Multi Operators Message on 9 August 2005, recommending to all B777 operators that the aircraft should not be flown with an unserviceable SAARU.

Edited September 18, 2005 by H Azmal

[Gavin Andrew David 6]

Good info , good info

[kandiah k 0]

Phew !!!!!!