Refer to a note TFU (Technical Follow Up) from Airbus TFU Ref 34.13.00.005 first issued Nov 1995 :
" Operators have reported airspeed discrepancies while flying under heavy precipitations or freezing conditions, which sometimes led to the autothrottle and the autopilot disconnection, THE E/W "F/CTL ADR DISAGREE" AND "F/CTL ALTN LAW"........
Strong Cumulonimbus containing a high density of ice crystals can be encountered, particularly in the intertropical convergence zone (ITCZ).
In such icy and turbulent atmosphere, the Aircraft Air Data parameters (Pressure Dependant) may be severely degraded, even though the probe heaters work properly.
It has appeared that the characteristics of such an environment could exceed the weather specifications for which the pitot probes are currently certified. "
Referring to AFP (Agence France Presse) article reproduced below, Air France A330 and A340 had previously encountered problem in flight with the anemometric system. The replacement of all Pitot Probe ot AF Airbus's fleet following recommendation edited by Airbus in September 2007 was launched since April 27, 2009. Unfortunately, the pitot probe of A330, F-GZCP involved in the accident was not changed yet.
One of the 24 ACARS messages sent by the airplane was EFCS PROBE 1+2/2+3/1+3 specifying so that all probes was in default.
With all the above, it would be difficult to any pilot to fly an airplane without exceeding the limit of what it was certified. Specially in bad weather.
Question : The problem was known since 1995. Why such long time for correcting the default ?
Paris, 06 June 2009 - 23:09 local time
Following the many questions which have appeared in the media on the issue of the Pitot probes in its fleet (the Pitot probe is an instrument which measures the air speed of the aircraft), Air France wishes to make the following clarifications:
1) Malfunctions in the Pitot probes on the A 320 led the manufacturer to issue a recommendation in September 2007 to change the probes. 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.
It should be noted that a recommendation from the manufacturer gives the operator total freedom to apply the corresponding guidelines fully, partially or not at all. Should flight safety be concerned, the manufacturer, together with the authorities, issues a mandatory service bulletin followed by an airworthiness directive (AD).
The recommendation to change the probes was implemented by Air France on its A320 fleet where this type of incident involving water ingress had been observed. It was not implemented on the A340/330s as no such incidents had been noted.
2) 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 cruise levels, and reiterated the operational procedures well-known to the crews.
In the first quarter of 2009 laboratory tests suggested, however, that the new probe could represent a valuable improvement to reduce the incidence of high altitude airspeed discrepancy resulting from pitot probe icing, and an in service evaluation in real flight conditions was proposed by Airbus. Without waiting for the in service evaluation, Air France decided to replace all its probes and the programme was launched on 27 April 2009.
Without making any assumptions as to a possible link with the causes of the accident, Air France speeded up this programme and reminded its pilots of the current instructions issued by the manufacturer to cope with the loss of airspeed data.