Hunt for Flight Recorders to Resume in February.

The French Bureau d’Enquetes et d’Analyses (BEA) released an interim report yesterday on the June crash of Air France Flight 447 however a definitive answer to the question of what went wrong continues to elude the investigators.

Iced over Pitot tubes - devices that interface with the airspeed indicators - continue to be the only named factor in the crash. Airbus, the manufacturer of the A-330 aircraft, has identified 32 separate cases where two or more of the Pitot tubes, manufactured by the Thales Avionics Company, iced up between November 2003 and June 2009 when AF447 crashed in the Atlantic Ocean east of Brazil.

Airbus has advised carriers flying airplanes equipped with the Thales Pitot tubes to replace them with compatible devices made by the BF Goodrich Company headquartered in the US.

In a recent development, Air France Flight 445, tracing the same path from Brazil to Paris as AF447, was forced to descend rapidly this past November 29^th while in weather conditions similar to those that existed in June. French investigators are hopeful they can gain some insight from that incident that may help them understand more about what happened to AF447.

Some in France are blaming climate change as a possible reason for the Airbus problems however that seems unlikely since Boeing has no records of similar troubles.

Responding to a query from Bloomberg News Service, Boeing spokeswoman Sandy Angers said, “There are no current issues with or regulatory actions against the Pitot probes/airspeed sensors on Boeing products.”  In an apparent swipe at Airbus, their biggest rival, she continued, “Boeing airplanes and their systems are designed to perform safely in the event of unreliable airspeeds.”

The second comment would seem to be a continuation of the ongoing dispute over which Fly-by-Wire system is best: Boeing’s system where the pilot can directly intervene in the control of the airplane anytime problems arise or the Airbus system where the layers of computers can progressively fail until reaching a condition called Direct Law that provides limited control of the airplane through an interface.

Black Boxes

The best source of data needed to finally determine the cause of the accident is the so called black boxes and BEA has enlisted the aid of the US, UK, Brazil and Russia, as well as the French government, in another attempt to find AF447’s illusive Flight Data Recorder and Cockpit Voice Recorder.

Mini-submarines are slated to resume the search in February even though the geographic area to be explored is the size of Switzerland. It has underwater canyons as deep as 20,000 feet below the sea surface and the boxes’ “Pingers” stopped working 30 days after the crash so the odds are long. There is some hope however: The FDR and CVR were recovered by a mini-sub from the bottom of the Mediterranean Sea 11 years after the crash of an Italian DC-9.

More Clues Emerge

Some additional information emerged as to the crash sequence through examination of the wreckage and condition of the recovered bodies.

It’s now thought that the A-330 did not depressurize in flight and apparently hit belly first instead of breaking up in the air as first reported. Also, there was a large vertical speed component involved.

The first conclusion many pilots would draw from these findings is the Airbus was in an unrecoverable flat spin wherein it was revolving upright in a relatively stable manner about a vertical axis.

Until the FDR or the hull and wings are recovered however, it can’t be determined if there was a rotation or if the crew had recovered the airplane to level flight but ran out of time and altitude before they could arrest the sink rate.

The BEA has said that their investigation will probably take another year so a final answer is still somewhere in the future. In the meantime, all operators of Airbus aircraft have either completed the change over to different Pitot Tubes or are changing them out as rapidly as possible.

John Loughmiller is an Electrical Engineer, Commercial Pilot, Flight Instructor and a Lead Safety Team Representative for the FAA.