An interim report casts doubt on the theory that speed tubes caused fatal crash into Atlantic; a new search for the plane's black boxes will begin early next year
By Andrea Rothman and Gregory Viscusi
Editor's Note: An earlier version of this story incorrectly referred to oxygen containers being used.
(Bloomberg) — French investigators, no closer to determining what caused Air France Flight 447 to crash into the Atlantic Ocean in June, cast doubt on the plane's air-speed gauges and said they will resume their black-box search.
In a report published on its Web site today, the Bureau d'Enquetes et d'Analyses pour la securite de l'aviation civile, or BEA, the French investigator of aviation accidents, called for a new standard for the air-speed monitors, saying they may ice over at high altitudes.
"It was an inconsistency in the measurements that initiated the disconnection of the various flight control systems: autopilot, autothrust and flight director," the BEA said in the report.
The Airbus A330 went down on June 1 during a flight from Rio de Janeiro to Paris, killing all 228 people on board. The plane's black boxes, the two flight cockpit recorders, would help explain the final minutes before AF447 lost contact, after sending 24 automatic messages signaling that its speed sensors, or Pitot tubes, were malfunctioning.
The BEA said it has yet to pin down precisely what caused the crash. The report identified turbulence, and said the accident area experienced rain and icy conditions. It said there was no lightning in the area where the plane fell.
The investigators said they recommend the study of high- altitude cloud masses.
"Despite the extensive analyses carried out by the BEA on the basis of the available information, it is still not possible to understand the causes and the circumstances of the accident," it said.
The BEA last reported its findings Aug. 31, when it warned the probe could last another 1 years. Airbus SAS, the maker of the plane, has offered to help finance continued research efforts.
The BEA said they are preparing for the third phase of the search for the plane's flight recorders, which may start in February 2010. The first stage involved a search for the black boxes by seeking the "ping" they emit for about 30 days. The second part involved submarines using sonar to try to locate debris from the Airbus A330-200. Neither located the sensors, which are presumed to lie on the Ocean floor within an area that the BEA has said is as large as Switzerland.
"At this point, the lack of data from the flight recorders and of any observations about the flight, mean the exact circumstances and cause of the accident are still unknown. The investigation will continue."
The BEA said it will study the possibility of ejectable black boxes, and recommended that the pings on the boxes be extended to 90 days.
The third phase, which will aim to find the hull of the plane and the flight recorders, will involve investigators from the U.S., Russia, Germany, Brazil and the U.K, in addition to the French.
Flight data recorders have in the past been recovered long after they stopped emitting sounds. The mini-submarine used in the Flight 447 search recovered a flight recorder from an Aerolinee Itavia DC-9 from the floor of the Mediterranean Sea in 1991, 11 years after the plane crashed.
Boats from France, Brazil and other countries have recovered 51 bodies and 600 aircraft parts from AF447, including the tail section. The rest of the plane is presumed to have sunk.
To contact the reporter on this story: Andrea Rothman in Toulouse, France on firstname.lastname@example.org; Gregory Viscusi in Paris at email@example.com; Laurence Frost in Paris at firstname.lastname@example.org.