Boeing issues advice on 737 Max plane sensor after Lion Air crash

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howie
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Boeing issues advice on 737 Max plane sensor after Lion Air crash

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Post by howie » Wed Nov 07, 2018 12:31 pm

Boeing is advising airlines on procedures to deal with false readings from an aircraft sensor that authorities say malfunctioned on a 737 Max plane that crashed off the Indonesian coast over a week ago, killing all 189 people onboard.

The operations-manual bulletin was issued Tuesday, the US planemaker said in a statement posted to Twitter, and tells crew to use existing guidelines when dealing with erroneous inputs from the so-called angle of attack sensor. That sensor is intended to maintain airflow over a plane's wings but if it malfunctions can lead to an aerodynamic stall – which can cause aircraft to abruptly dive.
The bulletin is based on preliminary findings from the Lion Air disaster, a person familiar with the matter earlier told Bloomberg. Under some circumstances, such as when pilots are flying manually, the Max jets will automatically try to push down the nose if they detect that an aerodynamic stall is possible, the person said. One of the critical ways a plane determines if a stall is imminent is the angle of attack measurement.

The Lion Air 737 Max 8 jetliner plunged into the Java Sea minutes after takeoff from Jakarta airport on October 29, nosing downward so suddenly that it may have hit speeds of 96 km/h before slamming into the water.

Moments earlier, the pilots radioed a request to return to Jakarta to land, but never turned back toward the airport, according to Indonesia's National Transportation Safety Committee and flight-track data. The committee said the pilots were dealing with an erroneous airspeed indication.

The probe into what happened with the Lion Air plane "is ongoing and Boeing continues to cooperate fully and provide technical assistance at the request and under the direction of government authorities investigating the accident," the company said in its statement.

Indonesian authorities have downloaded information from the flight data recorder that showed a cockpit indicator on the Lion Air jet was damaged for its last four flights.

A search for the cockpit voice recorder, the second so-called "black box", remains underway.

On November 5, the Indonesian transportation-safety committee called on Boeing and the US National Transportation and Safety Board "to take necessary steps to prevent similar incidents, especially on the Boeing 737 Max, which number 200 aircraft all over the world," according to a statement.

Aircraft and engine manufacturers routinely send bulletins to air carriers noting safety measures and maintenance actions they should take, most of them relatively routine. But the urgency of a fatal accident can trigger a flurry of such notices.

After an engine on a Southwest Airlines plane fractured earlier this year over Pennsylvania, killing a passenger, CFM International issued multiple bulletins to operators of its CFM56-7B power plants.

Aviation regulators such as the US Federal Aviation Administration and the European Aviation Safety Agency often follow such actions by mandating that carriers follow the bulletins.

Pilots raise and lower the nose of Boeing jetliners by pushing and pulling on a yoke in the cockpit, which controls panels at the tail known as elevators. In addition, a system known as elevator trim can be changed to prompt nose-up or nose-down movement.

The angle of attack readings are fed into a computer that in some cases will attempt to push down the nose using the elevator trim system. In the early days of the jet age, the elevator trim system was linked to several accidents. If pilots aren't careful, they can cause severe nose-down trim settings that make it impossible to level a plane.

Such an issue arose in 2016 at Rostov-on-Don Airport in Russia when a FlyDubai 737-800 nosed over and slammed into the runway at a steep angle, according to an interim report by Russian investigators. That case didn't involve the angle-of-attack system. One of the pilots had trimmed the plane to push the nose down while trying to climb after aborting a landing, the report said. All 62 people on board died.



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Re: Boeing issues advice on 737 Max plane sensor after Lion Air crash

#2

Post by Bell 407 » Wed Nov 07, 2018 1:30 pm

Worrying indeed. Win7 always gives trouble on my PC so why not on an airplane :yikes:



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