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SCMP Reporter

PASSENGERS aboard a 1991 Lauda Air flight which crashed into dense jungle shortly after taking off from Bangkok airport may have unwittingly caused the disaster themselves, according to a new report.

  Fifty-two Hong Kong residents were among the 223 victims of Thailand's worst air disaster, caused by the reverse thruster on one of the Boeing 767-300's engines suddenly cutting in.

  Until now, crash investigators could not explain why the on-board computer had activated the thrusters. But a report by Britain's Civil Aviation Authority (CAA) suggests electromagnetic interference from a camcorder, a laptop computer or a mobile phone could have been enough to trigger the disaster.

  A CAA official said radio waves emitted by electronic equipment had been found to confuse on-board computers.

  'This may have led to unexplained crashes like the Lauda Air disaster, but nothing is conclusive yet,' he said.

  The Boeing was on a charter flight from Hong Kong to Vienna via Bangkok on May 26 when it crashed 160 kilometres northwest of the Thai capital.

  A September 1993 report by Thailand's Aircraft Accident Investigative Committee said the unintentional opening of the plane's reverser - normally used to help brake on landing - had caused the aircraft to veer violently while climbing at full power and at a relatively low altitude.

  The plane immediately lost 25 to 30 per cent of lift. Investigators said the aircraft dived almost at the speed of sound, with parts shearing off before impact.

  'There have been recorded incidents over the last two to three years indicating that certain electronic equipment operated by passengers may have confused or affected the navigation of the aircraft,' the CAA spokesman said.

  'A warning went out to UK airlines alerting them of this fact which subsequently led to the use of electronic equipment being banned during takeoff and landing.

  'Although the direct effects of [electromagnetic interference] have not been proven beyond technical doubt, our research will continue.'   Potentially dangerous equipment includes Nintendo games, laptop computers, compact disc players, mobile phones and camcorders.

  The investigation into the Lauda Air crash was hampered by the loss of data from the flight recorder; the heat on impact burned the tape.

  But Lauda Air area director Sunny Yee said the airline would follow the debate over electromagnetic interference with 'intense interest' and would not hesitate to introduce new safety regulations if required.

  'The use of mobile phones, laptop computers and other digital communications is prohibited on Lauda Air flights during takeoff and landing as a standard safety procedure,' he said.

  'Without further evidence and research, we cannot confirm any relationship between electromagnetic interference and an aircraft going into reverse thrust.'   Another British aviation expert said the reliability of computers made routine malfunction unlikely, suggesting some outside influence could have been the cause.

  'The probable cause is computer malfunction and there are very few reasons for malfunctions,' he said.

  'One is the misprogramming of software, and if this were the case the plane would have crashed during a much earlier flight. The other is stray signals from other electronic equipment confusing the computer.'   A recent UK Flight Safety Bulletin reviewed 97 incidents it said could have been caused by inflight electromagnetic interference. It cited problems such as: the autopilot mechanism disconnecting as a plane prepared to land because of signals from a mobile phone;   a jumbo jet losing all communication with ground control after a phone and computer were switched on in the business class cabin;   both compasses on an aircraft fluctuating wildly after one passenger began playing a Nintendo game and another used a camcorder;   an autopilot receiving false signals from ground beacons and turning significantly off-course after a passenger switched on a miniature television.

  A spokesman for the Thai Aviation Air Safety Division said the 1991 disaster was still being investigated. 'This is still a complete mystery,' he said.

  'Lots of suggestions have been put forward as to what caused the crash but nothing has been confirmed. However, we are looking into reports of the effects of electromagnetic interference as we are other possible causes.' 



New theory on Lauda crash