AVIATION/ BEA TO PROBE AIR FRANCE FL447 INITIAL SEARCHES

French investigators annnounced that they will re-examine acoustic data from the initial search for AIR FRANCE Flight 447 to determine whether the Airbus A330's flight recorders could have been located earlier. On May 1, day 700 of the search, the long-sought Flight Data Recorder's memory cylinder was located and raised on board the recovery vessel Ile de Sein, despatched to the crash site after the wreckage of the twinjet was finally discovered on April 3. It was followed, 34 hours later, by retrieval of the Cockpit Voice Recorder. France's BEA said it expects to receive the devices by the end of next week, when it will begin the task of assessing whether they contain any readable information. The BEA said it wants to understand whether it missed an opportunity to pinpoint AF447 during the 31 day acoustic hunt, map above, for the recorders' locator beacons, launched days after the fatal crash on June 1, 2009. "The area where the wreckage was found had been explored without detecting the beacon echoes," said the BEA director. "The reasons for this non-detection will now be sought". The Flight Data Recorder was damaged, with its memory cylinder separated from the interface electronics, and did not have its beacon attached. However, the BEA said that the Cockpit Voice Recorder's beacon was retrieved and will undergo analysis to see if it was functional. The BEA added that the beacon manufacturer put the transmission duration at around 40 days. The acoustic search started on June 10, 2009 and covered around 8500 square miles. This amounted to 74% of the initial target area surrounding the last known position of the aircraft, and crucially included the place where Flight 447 was eventually found. "When we compared our search]to what we did in the past, we noticed we were searching this area before," said the BEA. "The issue is to know whether the pingers stopped because they were out of order, due to the impact, or if we had not searched properly with the equipment".  The agency pointed out that the wreck was found at 12,800ft and the exploration marked the "first time we've searched at such a depth" The BEA said it will assess whether the equipment deployed in the acoustic phase was adequate for the task. While a nuclear submarine was used during the search, its sonar interceptor was not originally designed to pick up the 37.5kHz beacon signal. Lower-frequency transmissions, around 8.5-9.5kHz, would have improved the chances of this, said the BEA. But improved sensor settings enabled the maximum distance for detection to increase from 2000m to 3200m during the last 10 days of the acoustic search.