Defence station interference suspected in Qantas mishaps

The Weekend Australian ^ | 3rd January 2008 | Debbie Guest

[naturalman1975]

A MALFUNCTION has 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.

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.

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 the jet, also an A330-300 plunged suddenly and violently.

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.

[Yo-Yo]

If the flight control system can be remotely disabled by “defence station interference”, maybe it was a good thing that the KC-30 contract was canceled?

I thought the previous problem was an unauthorized mixture of different revisions of the Inertial Reference Units causing havoc when the Number 1 ADIRU?

[naturalman1975]

The ATSB have identified the ADIRU sending false data as the problem in October, but apparently haven’t yet worked out precisely why it happened - a second similar incident may cause a reassessment of the most likely theories.

[G Larry]

Oh my!
What if they disengaged the autopilot and actually flew the plane?

[Yo-Yo]

The A330 is a completely fly-by-wire aircraft. Pilot input goes to the flight control computer, which will interpret what the pilot desires, and combine that with the apparent attitude of the aircraft, then decide which control surfaces to move and by how much.

The flight control computer won't allow, for example, the pilot to induce an intentional stall, or to exceed the airframe maximum G rating, no matter how violently the pilot jerks on the control stick.

So, even with the autopilot off, the computer is still flying the aircraft, and the pilot is just one data point of input.

[G Larry]

I appreciate the information....but I’m less thrilled with your dampening my sarcasm.