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Naval Communications Station Implicated in Qantas Autopilot Interference |
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Monday, 05 January 2009 |
A malfunction in the autopilot system forced a Qantas jet to return to Perth, prompting concerns for the second time in three months that interference from a defence station in northwestern Australia may be to blame for a mid-air drama on the national carrier.
The Harold E. Holt Naval Communications Station provides very low frequency (VLF) radio transmission to United States Navy and Royal Australian Navy ships and submarines in the western Pacific Ocean and eastern Indian Ocean. With a transmission power of 1000 kilowatts, it is the most powerful transmission station in the Southern hemisphere.
Qantas flight 71 was on route to Singapore with 277 passengers about 8.30am last Saturday when it had to return to Perth after the jet's autopilot disconnected because of a problem with a unit that supplies key information to flight control computers.
The Airbus A330-300 was 45 minutes into the journey and about 380 nautical miles south of the Harold E. Holt Naval Communications Station - 15km north of Exmouth - when the autopilot switched off, The Australian reports.
After being notified that the plane was experiencing a problem with the air data inertial reference unit, the crew responded in less than a minute and followed revised operation procedures issued by Airbus after a similar emergency in October.
Seventy passengers were injured on that occasion, when their jet, also an A330-300 plunged dramatically.
Yesterday, the Australian Transport Safety Bureau said the latest incident would be investigated as part of the October emergency inquiry because it appeared to be "a similar event".
In a preliminary report on the October incident, the bureau said it did not know why the ADIRU started sending false data, keeping alive speculation that interference from the station might have contributed to or caused the problem.
Aircraft engineer Peter Marosszeky said yesterday it was possible that interference from radio transmitters at the station could have caused the malfunction in both incidents.
"Even though the plane was 260 nautical miles (from Exmouth), those radio transmission signals are very powerful when they are transmitted," Mr Marosszeky said.
"These signals are supposed to travel around the world to reach submarines in the water and naval vessels, so they are very powerful. Whether there was one being transmitted at the time I don't know but you certainly have to look at the event log at the station."
The Defence Department would not comment yesterday.
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