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Lethal Lion Air 737 crash review refers to automated systems that control the pitch pitch

Incorrect information from a sensor on the exterior of the planet has been identified as contributing to the crash of…

Incorrect information from a sensor on the exterior of the planet has been identified as contributing to the crash of the Lion Air Flight JT610 last week. Only on MAX is this sensor that can trigger indefinite movements of the jet’s horizontal tail, says an expert.

The security bulletin Boeing sent out Tuesday evening to all airlines flying its 737 MAX jet stations at least to a possible contributory cause of the lethal crash of the Lion Air flight that killed 189 passengers and crew last week.

Boeing Warning, which only concerns the MAX model in the Renton-based Single 737, emphasized an automated system designed to prevent a plan that stalls, but may be haywire if fake data is fed from a small blade sensitive sensor on the outside of the planet.

Although there is insufficient information to be sure of what caused the crash, the investigator’s attention is focused on the system that can move the jet’s horizontal tail to throw the nose up or down.

John Cox, a former pilot and chief executive officer of aviation security safety system, said that although a version of this automated system has been 737 since the first was built in 1

967. Only at MAX is this sensor that can trigger indefinite movements of the jet’s horizontal tail.

To counter the problem, if it occurs in airplane, should require a standard pilot procedure – one recently emphasized by Boeing in its security bulletin on Tuesday.

Because of that, Cox said he considered MAX safe and should fly in one morning without a doubt.

But he suggested accident investigators and Boeing’s own engineers must carefully study the incident chain on the Lion Air flight deck and how the pilots handled the chaos, which should be clear from the cockpit voice recorder, to determine if Boeing needs to fix system design.

Another expert, Bjorn Ferhm, an analyst with, a former jet pilot and airplane engineer, said that it is possible to change the internal logic of MAX’s airplane system could have been lost, believing that one more likely suspected is a hardware failure in the airplane on the specific aircraft that crashed.

He recalled that when an Airbus A320 powered by AirAsia in Indonesia was crashed in 2014, killed 162 people, the pilot also had to deal with a cascaded series of repeated instrument failures, as determined by accidents involving a fractured solder joint.

So Ferhm also believes that MAX is as safe as any 737. If anything happens to the pitch control system, pilots must only follow the procedures described in Boeing’s warning, he said.

Following the Boeing Security Warning, FAA issued on Wednesday an Emergency Airworthiness Directive, which immediately applied and required the airlines to update pilot procedures according to the instructions in the warning. FAA said the directive was based on an analysis carried out by Boeing.

An FAA engineer spoke with regard to anonymity said Boeing is bicycle pilots through 737 MAX simulators trying to understand how they react to the various instrument errors listed in the Lion Air crash.

If the accident investigation would ultimately find fault with Boeing’s design of the nose protection management system, it would be a question of the security certification process, many of which are delegated by FAA to Boeing itself. 19659003] Boeing on Wednesday declined to comment.

FAA mandate action

FAA said the directive addresses the potential effects of false information coming from the sensor on the outer surface of the planet which reports the plane’s “angular angle” (AOA), which is the angle between the wing and the airflow as the beam moves through.

This key data point is entered into the flight computer together with the temperature and air velocity. These three measurements affect each other and are used by different systems that control the flight of the flight.

FAA said false AOA readings “may potentially make the horizontal (tail) repeatedly throw the nose on the aircraft downwards, making the aircraft difficult to control.”

The danger that FAA warns is that this can “lead to excessive nose use, significant height loss and possible impact on the terrain “.

The Boeing service bulletin to the airlines notes that although pilots can retreat on the yoke and adjust the horizontal tail to get their nose torn back, the state that pulls the nose can then restart five seconds later.

Flight data of the Lion Air jelly in the 12 minutes before it crashed shows a pattern of the planet that repeatedly loses its height and regains it before it finally burned into the ocean.

Automated system that works on incorrect data

The problem is with the “machine”

When a pilot draws or presses the control column, he or she exerts a force to adjust the moving horizontal tail and raise or raise or lower the aircraft’s nose. Trimming means setting the system to keep the tail in that position without further effort from the pilot. The power of the control column is relaxed to zero and the system maintains the position.

A pilot can trim manually every time he adjusts speed or direction. Or he can set the system automatically so that it makes adjustments to hold the position.

However, if the automatic trim system is fed incorrect attack angle (AOA), it will go wrong.

If the sensor tells the system that the AOA is too high, the automatic system begins to touch the tail to point down the nose. Although the pilot corrects it by dragging the column, if the sensor continues to say that the AOA is too high, the system begins to throw the nose again.

“No other 737 is a system based on the angle of attack that will move (horizontal tail) trim. It’s unique to MAX,” said Cox, CEO of the aviation consultant. “I was surprised that a single attack indicator angle could lead to activation of this system. “

The FAA Directive urges operators to review the aircraft manual to give flight crew procedures exactly what to do when this condition occurs. Avoid the aircraft repetitively setting down.

The Boeing instructions indicate pilots as they should pull back tight to control your nose and then use a cutout switch to turn off the system that automatically trims the horizontal tail to maintain speed and level flight.

Instead of using this auto trim system, which goes wrong every 10 Second, the pilot must then manually adjust the trim positions every time he changes speed or rich tning.

But in the stress of a real life situation, it can not be that easy.

The FAA Directive tells operators that the fake AOA reading can create a cascade of false indications on the aircraft that can confuse the flight crew.

These include a continuous or intermittent shake of the control column and a low speed indication, both suggesting that the plane approaches a stall; increasing nose down forces, as the pilot must pull back heavily on the control column to counteract; and warning lights that indicate false flight speed and height reading.

Ferhm said it was a “runaway trim” scenario, where an automated system improves the air traffic lights, “is something you train for each aircraft”.

“It’s one of the most common situations you have,” he said. “You train for it and learn to turn off the system.”

Still, he said he would not jump to blame the pilots. He said that the airplane in the Lion Air jet beam suggests “they had hell up there” because they were fighting to control the planet.

“The airplane always throws basketball balls. Why they did not cut out the automatic trim system, we do not know. In some way, they did not break the breaker.” We need more information. We need to listen to the voice recorders to learn why these pilots were so stressed, says Ferhm.

All 246 MAXs fly worldwide, with 45 of them in the United States in southwest, american and united.

FAA in a statement said it “continues to work near Boeing and as a part of the investigation team on Indonesia’s Lion Air accident, may take further appropriate measures depending on the results of the investigation. “

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