Air France speeds up sensor replacement programme

Air France is accelerating a programme to replace the airspeed sensors on all its A330 and A340 aircraft. Some commentators have suggested that faulty airspeed instruments could have contributed to the loss of an Air France A330-200 on 1 June, while flying from Rio de Janeiro to Paris.

The airline stressed that it is not making any assumptions about a possible link with the causes of the accident, but it has speeded up the replacement programme begun in April, and has also reminded its pilots of the current instructions issued by the manufacturer to cope with the potential loss of airspeed data.

One of the instruments used for airspeed calculation is a Pitot probe. Malfunctions in the Pitot probes on the A320 led the manufacturer to issue a recommendation in September 2007 to change them. This recommendation also applies to long-haul aircraft using the same probes and on which a very few incidents of a similar nature had occurred.

Operators are free to decide how to respond to such a recommendation. Should flight safety be concerned, the manufacturer, together with the authorities, issues a mandatory service bulletin followed by an airworthiness directive (AD).

Air France changed the probes on its A320 fleet, where this type of incident involving water ingress at low altitude had been observed. It did not make replacements on the A340/330s as no such incidents had been noted.

Starting in May 2008 Air France experienced incidents involving a loss of airspeed data in flight, in cruise phase on A340s and A330s. These incidents were analysed with Airbus as resulting from Pitot probe icing for a few minutes, after which the phenomenon disappeared. Discussions subsequently took place with the manufacturer. Air France asked for a solution which would reduce or eliminate the occurrence of these incidents. In response to these requests, the manufacturer indicated that the probe model recommended for the A320 was not designed to prevent such incidents, which took place at high-altitude cruise levels, and reiterated the operational procedures well-known to the crews.

However, laboratory tests in the first quarter of 2009 suggested that the new probe could reduce the incidence of high altitude airspeed discrepancy resulting from Pitot probe icing, and Airbus proposed an in-service evaluation in real flight conditions. Without waiting for the in-service evaluation, Air France decided to replace all its probes and the programme was launched on 27 April 2009.

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