NTSB probes two incidents involving Airbus A330s
By Joan Lowy
WASHINGTON — Federal safety officials said Thursday they are investigating two incidents in which airspeed and altitude indications in the cockpits of Airbus A330 planes may have malfunctioned, including 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 said in a statement that the first incident occurred May 21 when TAM Airlines Flight 8091 flying from Miami to Sao Paulo, Brazil, experienced a loss of primary speed and altitude information while cruising.
The board said initial reports indicate that the flight crew noted an abrupt drop in the outside air temperature reading, followed by the loss of a computer system that supplies information on airspeed and altitude. The autopilot and autothrust also failed.
The flight crew used backup instruments, and airspeed and altitude data was restored in about 5 minutes, the board said.
The board only recently became aware of the incident, but it confirmed the event through the Brazilian government.
Information on the second incident is more sketchy, but it involves a Northwest Airlines flight from Hong Kong to Tokyo on Tuesday, the board said.
Data recorder information, aircraft condition monitoring system messages, crew statements and weather information involving that flight are being collected by NTSB investigators.
In both cases the planes landed safely and no one was injured, the board said.
Airbus officials didn’t immediately return a phone call from the Associated Press.
Air France Flight 447 came down in the mid-Atlantic on May 31 after running into thunderstorms en route from Rio de Janeiro to Paris. The Brazilian military has led the search and recovery efforts for bodies and debris, while the French are in charge of investigating the crash and the hunt for the flight recorders, or black boxes.
The cause of the crash is unclear. Without the black boxes to help explain what went wrong, the crash investigation has focused on a flurry of automated messages sent by the airliner minutes before it lost contact. One suggests that external speed sensors may have iced over, destabilizing the plane’s control systems.
The automated messages were not alarm calls and no distress call was picked up from the plane.
Air France has replaced the speed sensors, called pitot tubes, on all its A330 and A340 aircraft, under pressure from pilots who feared a link to the accident.
Two incidents could provide important clues to what caused the Air France crash or they could turn out to have no relationship to it, 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 Flight 447 also experienced a failure of the computer system that supplies key data like airspeed and altitude, Goglia said, that could explain the crash because when that happens "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.
The NTSB is a party to the Air France investigation because the plane’s engines and some of its cockpit navigation and communications systems came from U.S. manufacturers.