Australian Airbus incident unlikely to be relevant to Air France disaster

3rd June 2009 By: Keith Campbell - Creamer Media Senior Deputy Editor

Speculation that the loss, early Monday morning, of Air France Airbus A330-200 F-GZCP, flight number AF447, could be connected with an alarming incident that befell a Qantas A330 last year is almost certainly erroneous.

In October, a Qantas A330 flying over Western Australia at some 12 000 m, suddenly and unexpectedly dived steeply, throwing around everyone who was not strapped in to their seats. The aeroplane dropped some 200 m before the flight crew regained control and levelled it out.

Australian investigators identified the cause as a fault in one of the aircraft’s flight data computers, although the exact fault has not yet been revealed. The unit in question is designated an Air Data Inertial Reference Unit (Adiru). This gathers data on aircraft altitude, speed, the outside air temperature, and many other parameters, and feeds it all into the flight control computers.

Somehow, the Adiru on this Qantas aircraft malfunctioned and gave the flight control computers data which indicated that the aeroplane was climbing steeply. So the flight computers sought to restore the A330 to what they thought to be level flight. As the aircraft was actually flying straight and level at the time, the result was to throw it into a steep dive. More than 50 people suffered varying degrees of injury as a result.

Obviously, should such an event befall an aircraft flying through a severe storm, the result could be disastrous.

But the Adirus fitted to Qantas A330s are manufactured by Northrop Grumman, while the Adirus which equip Air France come from a completely different manufacturer, Honeywell, and are to a totally different architecture. The chances of the same fault developing in both is thus minutely small.

The French air accident investigation agency, the Bureau d’Enquetes et Analyses (BEA), has already warned against “hasty interpretation” of “fragmentary” information. Under Annexe 13 of the International Convention on Civil Aviation (also known as the Chicago Convention), the BEA is reponsible for the investigation into the loss of F-GZCP, with the Brazilian authorities providing all necessary support.

Meanwhile, the Brazilian Navy hopes to start the recovery of debris from AF447 later on Wednesday. Bad weather has slowed the progress of the three warships that sailed on Monday to participate in the search for the lost aircraft.

Significantly, the debris was found floating in an area some 150 km south-east of the last known position of F-GZCP. This means that the searchers are still far from finding the actual wreckage of the aircraft on the sea bed.

Locating the wreckage will require the use of specialist vessels, and France has already ordered a research ship, equipped with two deep-diving mini-submarines, to the area.

Even so, French officials are cautioning that the wreckage may not be found and, even if found, that the flight data and cockpit voice recorders – the “black boxes” may not be retrievable. They could lie as much 3 000 m below the surface.