Article Posted on : - Oct 15, 2008

Qantas is considered one of the safest airlines but the recent incidents have dented its image

LONDON (BNS): Airlines operating Airbus aircraft have received an alert after Australian investigators claimed that a defect in autopilot system onboard an A330 of Qantas Airways resulted in its sudden drop of altitude on October 7, causing injuries to several passengers.

The Australian Transport Safety Bureau (ATSB) claimed that the Airbus A330-300's flight control system did not get correct information from the computer causing it to drop suddenly by 650 feet midair. The aircraft was cruising on autopilot at 37,000 feet when it nose dived hurling passengers and crew in the cabin.

Airbus has issued a telex yesterday asking operators of A330s and A340s alerting them about the abrupt behaviour, claimed Australian media reports. The Australian authorities, however, feel that the snag was a "unique event".
ATSB has put up some information about the investigations on its website. It said that one of the three air data inertial reference units gave wrong input resulting in autopilot to get disengaged.

The statement said the crew steered the aircraft manually till the end of the flight. ATSB noted even without autopilot being active, the flight control system command control surfaces to protect aircraft from dangers like stalling.

But in the Qantas incident, incorrect stall and speed warnings to the aircraft's primary computer were fed. Around two minutes after the fault, it generated very high, random and incorrect values for the aircraft's angle of attack.

This resulted in flight control computer to initiate a nose-down aircraft movement causing lowering of pitch by 8.5 degrees. Investigators have also pointed out that such an incident has not been reported from any other Airbus aircraft.
The incident had caused panic and raised serious questions about the flight safety standards of the Australian airline. A series of mid-air scare had forced the Australian authorities to review maintenance schedule of Qantas fleet.

The maintenance standards were not found to be up to the mark. ATSB said that its investigation into the A330-300 incident has still not concluded. The investigators continue to look for other leads that could point what caused the computer to feed incorrect information.

Qantas was considered to be one of the safest airlines but the recent incidents have dented its image.