Change to 737 MAX controls may have imperiled planes, experts say

[Eugene]

Source: Reuters

Change to 737 MAX controls may have imperiled planes, experts say

By Alwyn Scott, Wen Foo and Eric M. Johnson

PUBLISHED MARCH 22, 2019

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.

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.

-snip-

ENGINE CHANGES

The 737 MAX has larger and more fuel-efficient engines that are placed higher and fUrther forward on the wing, changing the jet’s balance and how the jet handles in certain situations.

-snip-

Read more: https://graphics.reuters.com/ETHIOPIA-AIRLINE-CONTROLS/0100916V1NZ/index.html

[Wellstone ruled]

1. Boeing knows a Class Action is coming to the tune

of a Billion dollars. It is all about the cover up and running the Clock.

[JayhawkSD]

2. The first statement is a misunderstanding.

"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."

No. Before the MAX conversion, there was no automatic trim system to be turned off. The automatic trim is part of the MAX conversion, and is Boeing's "fix" to aerodynamic instability caused by bad engineering. They fitted physically larger engines onto an airframe which could not accommodate those engines. That is summed up here:

"The 737 MAX has larger and more fuel-efficient engines that are placed higher and fUrther forward on the wing, changing the jet’s balance and how the jet handles in certain situations."

The "larger" does not mean "more powerful." It means bigger in diameter, much bigger, and heavier. It makes the plane fly differently, which should have meant retraining the pilots. To avoid the expense of retraining the pilots, Boeing put some software in to make it seem like it was flying the same. Not only did the software fail to safely accomplish its purpose, it took control of the airplane away from the pilot.

So, tugging on the controls of older model Boeing 737s did not shut off anything, because older 737s did not have anything that needed shutting off.

[CaptainTruth]

3. I'm no expert, but I thought the "yoke jerk" disengaged the autopilot on older 737s?

[JayhawkSD]

4. Yes, it did, and does.

But it did not disengage the "automatic trim system" on older models, because older models did not have an "automatic trim system" and did not need an "automatic trim system."

Pretty much all airplanes have autopilots system, and pretty much all of them disengage whenever the pilot make manual input with any of the controls. In the same way, stepping on the brake pedal of your car disengages the automatic speed control.