The European Aviation Safety Agency (EASA) has released a Proposal for an Airworthiness Directive (PAD) requiring all Airbus A330 and A340 aircraft currently equipped with Thales pitot probes should be equipped with Goodrich pitot probes on position 1 (Captain) and 3 (Standby) instead, while pitot probe 2 (first officer) should be upgraded to the enhanced Thales pitot probe type BA or to the Goodrich pitot probe.
The PAD reasons
Occurrences have been reported on A330/340 family aeroplanes of airspeed indication discrepancies while flying at high altitudes in inclement weather conditions. Investigation results indicate that A330/A340 aeroplanes equipped with Thales Avionics pitot probes appear to have a greater susceptibility to adverse environmental conditions than aeroplanes equipped with Goodrich pitot probes.
A new Thales Pitot probe Part Number (P/N) C16195BA has been designed which improves A320 aeroplane airspeed indication behaviour in heavy rain conditions. This same pitot probe standard has been made available as optional installation on A330/A340 aeroplanes, and although this has shown an improvement over the previous P/N C16195AA standard, it has not yet demonstrated the same level of robustness to withstand high-altitude ice crystals as the Goodrich P/N 0851HL probe. At this time, no other pitot probes are approved for installation on the A330/A340 family of aeroplanes.
Airspeed discrepancies may lead in particular 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 the prevailing aeroplane altitude and weather, this condition, if not corrected, could result in reduced control of the aeroplane.
For the reasons described above, this AD is a precautionary measure and requires the removal from service of all Thales Avionics P/N C16195AA pitot probes, the replacement of Thales Avionics P/N C16195BA pitot probes at positions 1 (Captain) and 3 (Stand by) with Goodrich P/N 0851HL probes and the installation at position 2 (First Officer) of a Thales Avionics pitot probe P/N C16195BA. This AD is considered to be an interim measure and further AD action cannot be excluded.
The upgrade is to be accomplished within 4 months after the Airworthiness Directive (AD) becomes effective. EASA is open for consultation on this proposal until September 7 2009.
Readers will observe the Aero-Instruments 0851HL-AI Pitot Probe , recently approved by the US Federal Aviation Administration for use on all Airbus A320/A330/A340 families of aircraft, is not mentioned in the EASA PAD.
Hat tip to Simon Hradecky at AVHerald for the story.