Air France Flight 447 was Awaiting Anemometric Sensor Replacement
Air France will be replacing the anemometric sensors on all Airbus jets which gives possible clues to the loss of Air France Flight 447. The sensor is a vital instrument and Flight 447 was awaiting sensor replacements as investigators identify the sensors as a likely contributor to the accident.
Thales SA created the sensors which consistently gave inaccurate speed readings on the Airbus A330 jet from Rio de Janeiro to Paris on June 1. Airbus SAS have been advising airlines for more than a year to replace the sensors on A330 jets to a model that are less vulnerable to ice.
France’s chief crash investigator today told journalists at a briefing near Paris that the failure of the air sensor to convey reliable speed data may have kicked off the chain of events that led to the deaths of all 228 people aboard.
In press release N 12, Air France acknowledges the malfunctions in the Pilot probes on A320 which was recommended in September 2007. The recommendations from the manufacturers gave Air France the freedom to apply to the guidelines fully, partially, or not at all. Although not mandatory, Air France accepted the reccomendations and implemented the changes on the A320 fleet but not on the A340 and A330s.
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.
The Press Release continues to have Air France acknowledging the new probe could improve the reduction of high altitude airspeed discrepancy from probe icing. Air France decided to replace all its probes in a programme that was launched on April 27, 2009.
The sensor on the A330 is a so called Pilot-tube which was named after a French engineer who discovered in the 1700s that the pressure of a gas or liquid through a tube could be used to determine velocity.