One of the articles this one links to [1] makes what might be a significant point, at least with regard to the Lion Air crash: "[The MCAS-commanded trim change

One of the articles this one links to [1] makes what might be a significant point, at least with regard to the Lion Air crash: "[The MCAS-commanded trim change] can be stopped by the pilot counter-trimming on the yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the pilot pulling the yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the pilot pulling so hard on the yoke that the aircraft is flying close to stall. "It’s probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn’t. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the pilots pulling against it. The faulty high AOA signal was still present. "How should they know that pulling on the yoke didn’t stop the trim? It was described nowhere; neither in the aircraft’s manual, the AFM, nor in the pilot’s manual, the FCOM." From other sources, it seems that Boeing's decision not to reveal this feature was justified, in part, on the grounds that the documented procedure for dealing with a trim runaway was the same as for preceding versions of the aircraft. This does not seem to have taken into account that the pilots' experience would differ from what they had been led, through their training, to expect, and likely to cause confusion over what was going on. Of course, now that this has come to light, one would hope that every 737-MAX pilot would have by now been well-prepared to handle the situation - unless there is some additional issue which has not been identified yet. [1] https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/ https://leehamnews.com/2018/11/14/boeings-automatic-trim-for...