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Southwest Replaced Flight-Control Sensors of the Type Implied in Lion Air Crash

During the three weeks before the Lion Air Flight 610 entered water outside of Indonesia,Southwest AirlinesCo.replaced two function flow sensors…

During the three weeks before the Lion Air Flight 610 entered water outside of Indonesia,

Southwest Airlines

replaced two function flow sensors of the same type that have been publicly involved in the crash, according to a summary of Southwest Maintenance records reviewed by The Wall Street Journal.


737 MAX 8, the same model that crashed last month in Indonesia. The sensors measure whether the jet line is angled over or during plane flight. These sensors, or related hardware, needed repairs in southwest bodies, according to the summary document. The document also shows that southwest pilots reported that they could not engage in automated gas settings, which resemble cruise control on a car.

A southwestern spokesman said the sensors did not fail and were removed as a precautionary measure as part of a troubleshooting process. She said at least one was repaired.

Investigators have confirmed the same type of sensor that failed on the Lion Air flight, but they have not determined exactly what happened between the failure and the crash.

Since the accident, which killed 189 people, Boeing has warned airlines about the potential of incorrect data from what are called angle-of-attack sensors. “We have not experienced a sensor error or flight problem as described in Boeing’s bulletin,” said the Southwest spokeswoman.

Southwest incidents did not result in emergencies and no one was injured. They asked what seems to be routine reports by mechanics who check out the problems with the sensors. One written on October 9 in Baltimore and the other October 21 in Houston shows the documents, and they indicate that both sensors were repaired.

Flip the Switch

Returning to the yoke will not stop a stall prevention system in Boeing’s new 737 MAX plane from pushing down the nose if there is bad sensor data. But to turn off the system will come.

In Boeing’s older 737 models,

a common practice to pull back on the control column (oket) stops the cockpit systems from automatically pushing down the planet’s nose.

In Boeing’s new 737 Max models,

which retracts, it will not work if its stall protection system receives incorrect data from the sensors.

But an existing procedure works for both:

Pilots flip switches to keep the plane from pushing down the nose.

Just eight days later, just after the Lion Air jets took off from Jakarta on October 29, an attack sensor on that flight sent incorrect data to flight computers, according to Indonesian and American investigators. Boeing and the Federal Aviation Administration later sent high priority security warnings that stressed that the problem arose. The resulting sequence of events is the core of the International Crash Probe.

Boeing and FAA did not have any immediate comment on the southwest documents. Southwest spokesman said the carrier replaced the two sensors in October on the same aircraft and decided that they were not the source of the automatic throttle. Two other Southwest 737 MAX 8s had replaced an angle-of-attack sensor as part of routine maintenance due to external damage, such as a bird’s stop in flight.

Security experts point out that it’s too early for definitive answers about LIon Air tragedy because a host of other factors were at stake. But so far, investigators have suspected that attack swing problems may have affected a variety of interactions between different flight control computers and pilots leading to the crash.

Within the next few weeks, Boeing and FAA are expected to agree on a mandatory security fix that changes some MAX 8 flight control programs, according to industry and officials involved in or tracking the process. The most likely change, they say, will turn off automatic nose commands in case there is a big difference between angle-of-attack data flowing to the captain’s and the mediocre’s cockpit screens. Some officials anticipate action as soon as two weeks.

As part of the cooperative US-Indonesian effort to tear up the complex interaction between automated systems and Lion Air cockpit staff, investigators are now investigating the lessons they learned over the years about potentially bleak consequences of defective or unreliable attack indicators , according to US authorities and industry safety experts.

Planning engineers and aviation security regulators have long realized and managed air traffic hazards arising from such malfunctions on a number of other models, including Airbus SE A330 and A340 aircraft, as well as standard A320 and A321 jet jets from the European manufacturer.

An important aspect of the Lion Air probe is to investigate whether Boeing engineers and technical managers-supervised by FAA-fully incorporated the previous lessons in the design of cockpit automation for the 737 MAX 8 and the MAX 9 fleet. There are currently over 200 Max variants delivered worldwide, of thousands of a total of 737s.

New Model Certification Processes “include considerations about applicable lessons from in-service events and events,” said a FAA spokesman in a written statement on Thursday, but “one has to take care of comparisons as aircraft systems are not all the same and respond differently on sensor inputs. “

The spokesman confirmed that looking back at past security events, including those caused by anxiety disorders, and how the agency responded to them – is part of the ongoing investigation. “

Since the October crash, Boeing officials have refused to discuss the probe or air traffic control survey now under review and say they help and collaborate with investigators and regulators.

Without developing the Chicago planetary manufacturer, it has said that the latest 737 models are safe and Pilots have previously provided adequate checklists to counteract risks for repeated and automatic nose commands. Boeing has also said it is “taking all steps to fully understand all aspects of the crash.”

But at this time Many of the investigative works led by Indonesian authorities, but assisted by US crash investigators, FAA and Boeing regulators – seem to focus on potential hazards arising from problematic attack values.

Lion Air pilots have stated that they were not informed about it new flight control systems that have been implicated a v investigator before the crash.

“Not only me but others too,” said Yusni Maryan, a leading pilot for the airline in Indonesia flying the MAX jets. “[Boeing] did not specifically mention it.”

Boeing has not commented on communication with specific airlines or their pilots.

Write to Andy Pasztor at [email protected] and Andrew Tangel at [email protected]

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