Air Transport

French investigators have this morning confirmed that automatic messages transmitted by the Air France Airbus A330-200 lost four days ago show that the aircraft was experiencing conflicting airspeed information from its on-board sensors.

The brief statement from investigation agency BEA follows the issuance by Airbus of a telex to operators reminding them of immediate actions to be taken by crews in the event of unreliable airspeed indications.

It says: "Many more or less accurate or attempted explanations of the accident are currently circulating. The BEA reminds one that in such circumstances it is best to avoid any hasty interpretation or speculation based on fragmentary and unvalidated information."

© Airbus

At this stage of the investigation, it says, the only elements established are:

• The presence near the planned route of the aircraft over the Atlantic of signifcant convective cells characteristic of the equatorial regions
• From the automatic messages transmitted by the aircraft, the inconsistency of the different measured speeds.

The Airbus telex states: "The route of the aircraft was crossing a tropical multicell convective area at the time of the accident. Failure/maintenance messages have been transmitted automatically from the aircraft to the airline maintenance centre.

"The above mentioned messages indicate that there was an inconsistency between the different measured airspeeds. Therefore, and without prejudging the final outcome of the investigation, the data available leads Airbus to remind operators what are the applicable operational recommendations in case of unreliable airspeed indication."

It then provides operations manuals references for the entire Airbus-fielded fleet of aircraft.

A 2001 airworthiness directive previously mandated operators to ensure that aircraft flight manuals were updated with the procedures in the event of unreliable airspeed indications following a series of such events on the type. It indicated that severe icing of the pitot tubes or physical loss of the radome, which additionally requires an increase in power to counter the drag, were potential causes.

Sources in Brazil familiar with the investigative work say that icing is a key focus of investigation.

• Kieran Daly thinks the icing question may be crucial. Read his blog.
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