[conspire] Ethiopian Air was following the emergency checklist

[Rick Moen]

A couple of hours ago, I wrote:

[NYT article quoting the Ethiopian preliminary report:]
 
>   The pilots countered [MCAS] by pushing electrical switches on their
>   control wheels that adjusted the angle of stabilizers on the tail of the
>   plane, which had been moved by MCAS. About five seconds after the pilots
>   tried the right the plane, MCAS again engaged, moving the stabilizers to
>   a dangerous angle in another nose-down action.
> 
>   The pilots pushed the electrical switches again. Then, the report says,
>   they followed the emergency checklist and disabled the entire stabilizer
>   electrical system using the so-called stabilizer trim cutout.

Here's a brand-new additional twist to that story, and, wow, just when
you thought this couldn't get more peculiar....

https://theaircurrent.com/aviation-safety/vestigal-design-issue-clouds-737-max-crash-investigations/

  Vestigial design issue clouds 737 Max crash investigations
  A 53-year old idiosyncrasy in the 737's design is expected to become a
  focus of the inquests.

Article starts out by recapping the Ethopian preliminary findings:

  The seeds of an intensifying crisis in 2019 with the planet’s most
  popular commercial airliner may have been planted more than a
  half-century ago.

  Five months after the crash of Lion Air 610, every Boeing 737
  Max-trained pilot on the planet was familiar with the MCAS system. They
  knew how it worked and knew how to disable it should they find it
  behaving in a way that put their airplane in danger. Flipping two
  cut-out switches would be sufficient, according to the Boeing guidance
  as part of the memorized checklist to troubleshoot errant movement of
  the horizontal stabilizer trim. Then crews would manually hand crank the
  jet’s trim wheel to right the nose. At least initially, the crew of
  Ethiopian 302 did just that, according to the preliminary report into
  the crash released Thursday.

  The recovery effort didn’t succeed and the trim wheel didn’t raise the
  jet’s nose. According to the 33 page report, the crew reactivated the
  electronic trim controls, causing the MCAS system to activate and push
  the jet’s nose down for a fourth and final time. With little altitude to
  recover, the 737 Max impacted the ground near Bishoftu, Ethiopia,
  killing all 157 aboard. The crash sparked the global grounding of the
  737 Max days later.

So far, so familiar.  But wait;

  The non-responsive trim wheel and the crew’s initial by-the-book
  efforts to save aircraft are expected to be an increasing focus of the
  myriad of inquiries into the 737 Max and its automated flight control
  system, according to air safety experts. But a vestigial design
  idiosyncrasy in the 737 may offer one clear explanation according to a
  former Boeing flight controls engineer, Peter Lemme, along with the
  procedures for recovering a badly configured 737 horizontal stabilizer
  that date to the early 1980s and before.

Oh?

  Three generations of 737s ago, pilots flying the 737-200 — a slightly
  longer version of the original 1967 airliner — were trained that if the
  jet’s horizontal stabilizer tilts too far — pushing the jet’s nose
  downward — hand cranking the trim wheel won’t work (after flipping the
  cut-out switches) while at the same time pulling back on the controls,
  according to Lemme and an Australian pilot who sought anonymity to speak
  freely about his experience training on the 737-200.

  The trim wheel barely budges, but why?

  As pilots would pull on the jet’s controls to raise the nose of the
  aircraft, the aerodynamic forces on the tail’s elevator (trying to raise
  the nose) would create an opposing force that effectively paralyzes the
  jackscrew mechanism that moves the stabilizer, explained Lemme,
  ultimately making it extremely difficult to crank the trim wheel by
  hand. The condition is amplified as speed — and air flow over the
  stabilizer — increases.

In short, the recommended way to assert manual trim becomes impossible
because the airframe fights the pilots because of an adverse pattern
of aerodynamic forces.

There's a lot more.  The gist of it is that MCAS triggering quite
possibly tended to put the 737 MAX into a dangerous condition that would 
tend to make Boeing's emergency checklist for fixing runaway automatic
trim not work at all -- unless the pilots also knew about a very unusual 
recovery method known to 737-200 pilots in the early 1980s but removed
from manuals after 1982.  This method:

  If other methods fail to relieve the elevator load and control column
  force, use the "roller coaster" technique:  If nose-up trim is 
  required, raise the nose well above the horizon with elevator 
  control.  Then, slowly relax the control column pressure, and 
  manually trim nose-up.  Allow the nose to drop to the horizon 
  while trimming.  Repeat this sequence until the airplane is in trim. 

The odds of current pilots knowing of this emergency recovery procedure
from four decades back is slim to none -- though I expect this is now a
hot topic among pilots.

The more I hear on this story, the more I like Airbus.  Seriously.