Mon, Jun 15, 2009 - Page 7 News List

Air France jet sent rudder problem alarm

RUDDER LIMITER INOPERATIVE One of the 24 automatic messages sent by the aircraft minutes before it disappeared pointed to a problem in the rudder limiter


A burst of automatic messages sent by Air France Flight 447 before it crashed includes one about a problem with a rudder safety device, but lacks decisive clues as to what sent the jet plunging into the Atlantic Ocean two weeks ago, an aviation expert said on Saturday.

The industry official, who has knowledge of the Air France investigation, said that a transcript of the messages posted on the Web site EuroCockpit was authentic but inconclusive.

One of the 24 automatic messages sent from the plane minutes before it disappeared on May 31 with 228 on board points to a problem in the “rudder limiter,” a mechanism that limits how far the plane’s rudder can move. The flight was headed from Rio de Janeiro to Paris through an area of fierce thunderstorms.

The nearly intact vertical stabilizer — which includes the rudder — was fished out of the water last week by Brazilian searchers.

“There is a lot of information, but not many clues,” the official said, speaking on condition of anonymity because he is not authorized to discuss the matter.

The official said jets like the Airbus A330 that crashed automatically send such maintenance messages about once a minute during a plane’s flight. They are used by the ground crew to make repairs once a plane lands.

Martine del Bono, spokeswoman for the French investigative agency BEA, which is in charge of the crash probe, and Airbus spokesman Stefan Schaffrath declined to comment on the transcript.

If the rudder were to move too far while traveling fast, it could shear off and take the vertical stabilizer with it, which some experts theorize may have happened based on the relatively limited damage to the stabilizer.

The industry official, however, said the error message pertaining to the rudder limiter did not indicate it malfunctioned, but rather that it had locked itself in place because of conflicting speed readings.

Investigators have focused on the possibility that external speed monitors — called Pitot tubes — iced over and gave false readings to the plane’s computers.

“The message tells us that the rudder limiter was inoperative,” Jack Casey, an aviation safety consultant in Washington, said last week when the existence of the automatic messages was first divulged. “It tells us that for some reason it was no longer functioning. That is all the message means.”

“It does not give you any reason why it is not working or what caused it, or what came afterward,” Casey said.

Unless the plane’s flight data and cockpit voice recorders — the so-called black boxes — are found, the exact cause of the accident may never be known.

A French nuclear submarine is scouring the search area in the hopes of hearing audio pings from the black boxes’ emergency beacons.

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