Change To 737 MAX Controls May Have Imperiled Planes, Experts Say | 3/21/2019 | Staff
graceygracey (Posted by) Level 3
NEW YORK/SEATTLE (Reuters) – Much like tapping the brake pedal in a car to disengage cruise control, a sharp tug on the controls of older models of Boeing Co’s 737 used to shut off an automatic trim system that keeps the plane flying level, giving the pilot control.

But Boeing disabled the “yoke jerk” function when it brought out the 737 MAX, the latest version of its top-selling jet – and many pilots were unaware of the change, aviation experts told Reuters.

Difference - Pilots - Aircraft - Climbing - Takeoff

The difference may help explain why pilots struggled to keep their aircraft climbing after takeoff on two fatal 737 MAX flights less than five months apart that killed 346 people.

Pilots of a Lion Air flight that crashed in October scoured a handbook for answers as the plane repeatedly lurched downward in the first minutes of flight, Reuters reported.

Airlines - Flight - March - Similarities - Lion

An Ethiopian Airlines flight that went down on March 10 showed “clear similarities” to the Lion Air accident, aviation authorities said after seeing black-box data.

A pair of switches on the center console between the pilots will turn off the automatic trim and a mechanism, new on the 737 MAX, known as the Maneuver Characteristics Augmentation System, or MCAS, that is suspected of playing a role in both disasters.

Pilots - MCAS - Power - Plane - Pull

But pilots would have needed to know that MCAS existed, that it had unusual power to force the plane down and that “a hard pull on the yoke” would no longer turn off the automatic trim that uses MCAS, John Hansman, an aeronautics professor at MIT, said in an interview.

“That wasn’t clear to the pilots flying the airplane,” Hansman said. “The training material was not clear on that.”

Boeing - Aftermath - Lion - Air - Crash

Boeing declined to comment. In the aftermath of the Lion Air crash, Boeing pointed to long-established procedures that pilots could have used to handle a malfunction of the anti-stall...
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