
737MAX: Trim Cutout can be difficult to recover - themgt
https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html
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dboreham
My thoughts as someone with not much aerospace engineering knowledge: FFS why
on earth should it be so hard to just keep an airframe in controlled flight
under benign weather and mechanical conditions??

Isn't this the equivalent of expecting my Mom to know to reboot her car's
engine management computer in order to be able to steer away from an oncoming
brick wall?

I guess I find it astonishing that this kind of mid flight debugging is even
considered viable as an approach by the industry. Are they inspired by
Armstrong's manual override feats on the Apollo 11 landing descent?

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cjbprime
In theory, nothing here is obscure. Trim is a control that airplanes have that
cars don't. It's a very basic control, it's right there on the control column.
A mechanical or computer failure could cause the plane to mistrim itself, so
one of the most basic emergency responses that every airliner pilot knows is
how to disable the auto-trim and fix it manually. MCAS is a new way for
mistrim to happen, but there were already many others before.

It sounds like the main issue is that Boeing didn't predict that MCAS would
mistrim at such low altitude that you don't have time to disable the trim
motor and perform the recovery before the ground intervenes.

~~~
miketery
> nothing here is obscure

Boeing chose to have the indicators that show the trim is on as a separate add
on, not as a default feature (i.e. an indicator showing the trim is enabled).
This is beyond unsafe, and unethical by all measures.

For a car it would be like having cruise control turn on automatically and
accelerating (without telling you), and worse yet, when you brake to try to
control your speed, it doesn't disable or do anything (pulling on the steering
column did nothing). To disable you need to do something totally different
(which is unnatural for a human).

I hope this error is costly to Boeing, and that the FAA learns from this
experience. This should have never been certified.

~~~
cjbprime
> Boeing chose to have the indicators that show the trim is on as a separate
> add on, not as a default feature (i.e. an indicator showing the trim is
> enabled).

This is nonsense. The optional light was just an AoA disagree sensor. It
doesn't provide any information about trim.

