Air France pilots urge change in air-speed sensors

Clues to Flight 447's failure may lie in Airbus tail section found Monday. Some airlines are starting to replace the instruments, known as Pitot tubes.

The men and women who sit in the left seats of Air France’s Airbus 330s don’t know for certain what happened to flight 447.

But those pilots are certain that the Airbus air-speed indicators – known as Pitot tubes – might be the problem. And they’re demanding action.

On Tuesday, the French newspaper Le Monde reported that one of the three unions at Air France urged pilots to refuse to fly unless two of the three Pitot tube sensors on each aircraft are replaced.

Shortly before the Air France flight went down, the aircraft automatically sent 24 error messages to the Air France maintenance headquarters in Roissy, France. One of those early messages was reported to be the loss of the air-speed indicators.

Why is that critical?

If the Pitot tube, the primary instrument for measuring the aircraft’s speed, is faulty or giving a false reading because it is clogged by ice, that could result in the aircraft traveling too fast or too slow.

The French media have reported that the government agency investigating the crash has found that Flight 447's pilots may have been getting inconsistent airspeed readings as the plane passed through a thunderstorm.

In a US online aviation forum, one pilot observes:

Le Monde reports that “In a communiqué, Air France acknowledged that, since May 2008, "incidents of loss of anemometric information in cruising flight" on A330 and A340 had been recorded or acknowledged."

In other words, a year ago, it knew there was a problem.

Air France said Monday night that all 15 of its A330 and 19 of its A340 models were operating with at least one new pitot instrument, and nine of the aircraft have at least “two or three” of the new sensors.

The Associated Press reports that Eric Derivry, a spokesman for the SNPL union, the main union for Air France pilots, told France-Info radio that all Air France jets taking off Tuesday will be equipped with at least two of the new Pitot sensors. He also said that may lead to flight delays or cancellations.

Three airlines replace sensors

US Airways, Qatar Airways, and Aer Lingus announced Tuesday that they were replacing the air-speed sensors on their Airbus 330 aircraft. The sensors on the Airbus that is used by Brazilian President Luiz Ignacio Lula da Silva are also being replaced.

All this may just be erring on the side of caution.

In fact, in one pilot forum, it was observed that the stream of equipment failures automatically reported in the flight 447’s final minutes look more like an “explosion” or a “fire” than an icing problem. All three pitot tubes were lost at once, according to the automatic message sent by the aircraft to its maintenance headquarters.

Until the black boxes are found, no one knows what happened. It may have been turbulence or icing or a fire or something else. But the debris may begin to allow investigators to draw some conclusions.

Telltale Tail Section?
On Monday, the vertical stabilizer – or tail – of the Air France aircraft was recovered by the Brazilian Navy.

Based on the photos of the vertical stabilizer, it looks like a lateral fracture, William Waldock told the Associated Press. Mr. Waldock teaches air-crash investigation at Embry-Riddle Aeronautical University in Prescott, Ariz.

The orange boxes – the ones that record all the data and voice information during the flight – are located in the fuselage near the tail section. Finding the vertical stabilizer may help narrow the search for the boxes.

Listening equipment that can detect the “ping” from the boxes in deep waters is expected to arrive and get put to use by Thursday.