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Indonesian investigators said the indicators used by the pilot and the co – pilot aboard the Lion Air plane, dropped into the sea last week, indicated very different readings of a key parameter during the flight. a flight just before his last trip.
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, at the same time, issued a security warning Tuesday night on a potentially suspicious flight control software on the version of the plane that crashed. Boeing provided pilots with specific instructions on how to handle their new 737 Max 8 jets when they encounter confusing or inaccurate information.
Boeing warned that failure to process this information properly could result in a steep descent of the affected aircraft model. US aviation regulators said they were about to follow their own directive.
Boeing's warning is the first public indication that investigators are investigating a possible software problem (or misinterpretation by pilots) associated with an essential system that measures the "angle of attack" of an aircraft or indicates the tip of his nose. Flight 610 from Lion Air plunged into the Java Sea last week, killing 189 people on board.
This is the first major accident involving a Boeing 737 Max 8, the latest variant of its popular 737, which sparked a keen interest in the new model. The aircraft was delivered in August to Lion Air, one of Asia's largest low-cost carriers. Boeing participates in the investigation of the accident.
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Boeing's advice is an official warning to pilots, highlighting the potential dangers of the interaction of some software with other cockpit alerts.
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Boeing issued a bulletin to operators Tuesday night on how to deal with the problem. The warning stops before requiring or requiring the replacement or inspection of any specific onboard system. Nor is it a question of drawing a definitive conclusion as to whether a system failure led to a fatal accident.
The notification is instead an official warning to pilots, highlighting potential dangers arising from the interaction of certain software with various other cockpit alerts. Boeing reiterated the importance of following standard procedures in such circumstances.
Indonesian investigators separately said Wednesday that two of the jet's previous flights had had speedometer problems, after which the technicians chose to change an angle sensor to attack. The jet cockpit does not display an angle of attack measurement, but the readings are stored by the flight data recorder and are taken into account in the calculation of the speed. The indicated speed is then transmitted to the pilot and co-pilot in separate indicators in the cockpit.
After the replacement of the sensor, the jet aircraft was cleared to perform its penultimate flight. The investigators, citing information gleaned from the flight data recorder found from the jet, indicated that the angle of attack inputs for the pilot's and co-pilot's speed differed by 20 degrees during this flight. The problem was identified and corrected in flight by the crew, who was able to travel to Jakarta and requested a priority landing. The pilots flew manually for about an hour and 45 minutes, according to a person familiar with the subject.
The next day, during his last flight, the plane sank in the Java Sea at high speed and at a sharp angle.
Boeing said on Tuesday that his alert concerned cases "where there is an incorrect entry of a sensor (angle of attack)".
On the last flight of the aircraft, the crew returned to manual flight after having had unreliable indications of speed shortly after taking off from Jakarta in good weather, according to preliminary information gathered by the investigation. A few minutes after the crew informed the air traffic controllers of the situation and gradually gained altitude as part of an apparent effort to solve the problem, the twin-engine aircraft plunged into the Water at high speed.
-Robert Wall and I Made Senata contributed to this article.
Write to Ben Otto at [email protected] and Andy Pasztor at [email protected]
