Was it a rudder issue?

Divers from the Brazilian Navy recover a portion of the rudder of the missing Air France Flight 447.
AFP

RIO DE JANEIRO - 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, told AP that a transcript of the messages posted on the website EuroCockpit is 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 stabiliser - which includes the rudder - was fished out of the water earlier this 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 authorised 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. If the rudder were to move too far while travelling fast, it could shear off and take the vertical stabiliser with it, which some experts theorise may have happened based on the relatively limited damage to the stabiliser.

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," Mr Jack Casey, an aviation safety consultant, said last week. "It does not give you any reason why it is not working or what caused it, or

what came afterward."

Unless the flight data and black boxes are found, the exact cause of the accident may never be known. AP

From TODAY, World –Monday, 15-Jun-2009

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