The National Transportation Safety Board Examines Airbus Incidents

June 29, 2009 by Suzanne Conlon

Federal safety officials said Thursday they are investigating two incidents in which airspeed and altitude equipment on Airbus A330 planes may have malfunctioned.  The incidents include one that took place ten days before the same type of plane crashed into the Atlantic Ocean killing all 228 aboard.

The National Transportation Safety Board (NTSB) said the first incident occurred May 21, when a TAM Airlines plane experienced a loss of primary speed and altitude information while cruising. The flight crew noted an abrupt drop in the outside air temperature reading, followed by disconnections of the autopilot and auto-thrust, along with the loss of speed and altitude information. The flight crew used backup instruments, and that data was restored in about five minutes. NTSB only recently became aware of the incident.

The second incident involves a Northwest Airlines flight from Hong Kong to Tokyo on Tuesday, but there were no details available.  Following incidents, the planes landed safely and no one was injured. NTSB investigators are examining data recorder information, aircraft condition monitoring system messages, crew statements and weather information for the two incidents.

“These sources could provide important clues to what caused the Air France crash or not”, said former NTSB board member John Goglia.  "You just don't know yet," Goglia said, "but they would really be remiss if they didn't explore these possibilities."

If the doomed Air France flight experienced a similar failure, it could explain the crash. When that happens, Goglia said, "everything in the cockpit goes screwy — you have nothing to rely on. You speed up, you slow down. You go up, you go down. You have no reference," he said.

Air France Flight 447 crashed into the Atlantic after running into thunderstorms between Rio de Janeiro and Paris. Brazil has conducted the search and recovery efforts for bodies and debris, while France has been investigating the crash and hunting for the flight data recorders, or black boxes.

The cause of the crash remains unclear. Without the black boxes to explain what went wrong, investigators have focused on automated messages sent by the airplane minutes before it disappeared. One message suggests that external speed sensors, called Pitot tubes, may have iced over, which would undermine the plane's control systems. Under pressure from the pilots’ union, Air France has replaced the speed sensors on all its A330 and A340 aircraft.