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2009 Issues Archive
19 August 2009
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Airbus pitot probes to be replaced
The European Aviation Safety Agency (EASA) is to issue an airworthiness directive for more that 200 Airbus aircraft to have their airspeed pitot probes replaced.
The directive, which is at the proposal stage, says that all Airbus A330s and A340s fitted with pitot probes made by French firm Thales must be fitted with at least two probes from the US manufacturer Goodrich, allowing a maximum of one Thales probe to remain fitted to the aircraft. Each aircraft is fitted with three pitot probes in total.
The move comes as investigations continue into the cause of the fatal crash of an Air France Airbus in June.
The EASA said that under specific weather conditions, at high-altitude sub-tropical storm conditions, the Goodrich probe offered greater reliability than the Thales variant. It said that both Goodrich and Thales pitot tubes complied with the applicable safety standards, so the agency’s directive proposals were intended as a precautionary measure.
Airbus said that, on the basis of limited available information from the Air France accident, it has recommended that A330/A340 aircraft with Thales pitot probes should exchange at least two of them for Goodrich probes. “This affects 200 aircraft.”
Investigation by the EASA has revealed occurrences of airspeed indication discrepancies on A330/340 aeroplanes while flying at high altitude in inclement weather conditions.
The EASA proposal said: “Investigation results indicate that A330/340 aeroplanes equipped with Thales Avionics pitot probes appear to have a greater susceptibility to adverse environmental conditions than aeroplanes equipped with Goodrich pitot probes.”
It said that recently redesigned pitot probes from Thales designed for the A320 aeroplane had improved airspeed indication behaviour in heavy rain. But it said that the new variant “had not yet demonstrated the same level of robustness to withstand high-altitude ice crystals as the Goodrich probe”.
The proposal said that airspeed discrepancies could lead to disconnection of the autopilot and/or auto-thrust functions, and reversion to flight control alternate law, which would cause an increase of pilot workload. Depending on altitude and weather, this condition could result in reduced control of the aeroplane.
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© PE Publishing, 19 August 2009
