Pilots question airspeed sensors’ troubled history
PARIS – Airbus knew since at least 2002 about problems with the type of speed sensor that malfunctioned on an Air France passenger plane that went down in June, The Associated Press has learned. But air safety authorities did not order their replacement until after the crash, which killed all 228 people aboard.
The tubes, about the size of an adult hand and fitted to the underbelly of a plane, are vulnerable to blockage from water and icing. Experts have suggested that Flight 447’s sensors, made by French company Thales SA, may have iced over and sent false speed information to the computers as the plane ran into a thunderstorm at about 35,000 feet (10,600 meters).
The exact role the sensors — known as Pitots — played in the crash may never be known without the flight recorders, which have not been recovered and which have stopped emitting signals. Investigators insist sensor malfunction was not the cause of the crash, but many pilots think false speed readings may have triggered a chain of events that doomed the plane.
Fernando Alonso, head of Flight Operations at Airbus, maintains the doomed Airbus A330 plane was “totally airworthy.”
“There is no question for me the safety, the reliability of the airplane nor of the maintenance and operation procedures used by our operators,” he said.
The plane was flying from Rio de Janeiro back to the French capital when it went down in a remote area of the Atlantic, 1,500 kilometers (930 miles) off Brazil’s mainland and far from radar coverage. Automatic messages transmitted by the plane show its computer systems no longer knew its speed, and the automatic pilot and thrust functions were turned off.
Several European airline pilots, including former Air France captain Gerard Feldzer, believe a reading of the messages suggests Air France pilots were suddenly forced to take manual control in near impossible conditions: a cockpit ringing with warning bells and flashing lights, some of them contradictory, with few clues to speed, altitude and nighttime weather conditions.
“It’s very difficult when you are already experiencing turbulence in the middle of the night, to know what to do,” said Feldzer, adding that the plane’s automated warning system could have been issuing incorrect instructions. “It’s very difficult to resist what you are being ordered to do because they are false orders.”