French AF447 investigators have recommendations, no answers
Friday December 18, 2009
In its second interim report on the May 31 loss of the Air France A330-200 over the Atlantic, France's BEA issued its first safety recommendations and concluded that "In the absence of any data from the flight recorders, the main parts of the airplane and any witness testimony on the flight, the precise circumstances of the accident, and therefore its causes, have still not been determined."
Investigators' inability to recover the recorders "raise[s] questions about the adequacy of the means currently in use on civil transport aircraft for the protection of flight data with the technological possibilities and the challenges that some accidents represent." Consequently, it recommended to ICAO and EASA that commercial aircraft flying over water should be equipped "as rapidly as possible" with an additional locator beacon capable of transmitting on a frequency between 8.5 and 9.5 kHz and that transmission time of the flight recorder ULBs must increase to at least 90 days from the current 30. It also urged a study into the possibility of mandatory regular transmission of basic flight parameters.
Regarding the possibility that malfunctioning pitot tubes played a role in the accident, BEA said it analyzed 13 examples of the temporary loss of reliable indications of one or more airspeeds involving A330s/A340s operated by AF, TAM, Qatar Airways, Northwest Airlines and Air Caraibes. The events occurred in highly unstable air masses in the vicinity of deep convective weather phenomena, flight levels were between FL340 and FL390, static temperature was below -40C in 12 cases and turbulence was recorded each time
(ATWOnline, Dec. 17).
"The certification criteria are not representative of the conditions that are really encountered at high altitude, for example, with regard to temperatures," BEA concluded. "In addition, it appears that some elements, such as the size of the ice crystals within cloud masses, are little known and that it is consequently difficult to evaluate the effect that they may have on some equipment, in particular the pitot probes. In this context, the tests aimed at the validation of this equipment do not appear to be well-adapted to flights at high altitude."
It recommended that EASA study the composition of cloud masses at high altitude "with appropriate precision" and modify icing certification criteria in accordance with the results and in coordination with other regulatory authorities.
by Cathy Buyck
Air Transport World