Originally Posted by
LarryJ
It is not true. The author is confusing two different systems. (Or, if he understands it, he's presenting it in a way which leads others to be confused.
An unschedule MCAS activation can be overridden several ways by the pilots.
1. The easiest way to is use the primary electric trim switches, a set of which is on the outboard horn of each control wheel. These are the trim switches which a pilot uses to trim the aircraft when he is hand-flying. When either of these switches are activated during an MCAS activation, the MCAS activation is stopped and remains inhibited until five seconds after the trim switches are released. This would be the natural response to an airplane that is suddenly nose-heavy due to an unscheduled MCAS activation.
2. The primary and backup trim cutout switches below the throttles on the center console. Either of these switches will disable all electric trim including MCAS. These switches are used in the stabilizer runaway procedure (memory items) to disable all electric trim inputs.
3. Physically holding either of the trim wheels to prevent rotation. This is not something a pilot would normally do but it would work.
4. Extending the flaps. MCAS is inhibited with flaps extended.
What the article is talking about is the trim brake which is activated when control column movement opposes electric trim inputs. The trim brake does not stop MCAS because MCAS could not do its intended job if it did which is to increase the nose-down pitching moment at high angles-of-attack. By definition, you're going to be holding back-pressure in those situations and it is the job of MCAS to increase the amount of required back pressure. The trim brake is not something that a pilot would intentionally use to stop trim input. It works in the background to stop other scheduled trim inputs, generally from the speed trim system, when they aren't needed.
Not being a pilot, I would say that you have outlined actions which makes sense... once the pilot knows that there is a hidden software (MCAS) which is activating and controlling the aircraft.
If the operator knows about the software - dealing with it becomes much more straightforward.
But MCAS, as deployed, is malware. It's hidden from the operators and runs in a way which is NOT documented properly at all.
The highlighted portion illustrates the point that a powerful software function is altering the functions in an undocumented and unanticipated manner.
As you noted, 737 pilot does NOT expect to have to hold the trim wheels which suddenly start rotating on its own. Since pilots are human beings instead of robots, unexpected behavior which is outside the expected parameters creates confusion. The entire situation would have been avoided if Boeing hadn't focused on secrecy in order to get quick-certification without pilot retraining.
That's why, IMO, the blood of 300+ people are on the hands of Boeing executives and employees.
If they truly feel no guilt and no responsibility and believe the company line of "well, the pilots
could have saved the plane"... then they are (IMO) monsters.