>I will leave a discussion of the corporatization of the aviation lexicon for another article, but let’s just say another term might be the “Cheap way to prevent a stall when the pilots punch it,” or CWTPASWTPPI, system. Hmm. Perhaps MCAS is better, after all.
It's not actually just intended for when pilot's pour on the thrust, it's for any time they pour on the AoA. There need not be any throttle change involved to bring this about. The most readily imagined example, however, is low speed, large throttle increase like you'd have if you were aborting a landing attempt to go around.
>When MCAS senses that the angle of attack is too high, it commands the aircraft’s trim system (the system that makes the plane go up or down) to lower the nose. It also does something else: It pushes the pilot’s control columns (the things the pilots pull or push on to raise or lower the aircraft’s nose) downward.
Nothing I've read characterizes MCAS as having an inbuilt-stick pusher. I've mentioned before that MCAS shares a spot with stick-pushers in terms of what they are trying to do, and problem they are employed to solve but MCAS does not actively put force on the stick through an extra mechanism with the intent to actuate a control surface deflection, and alerting the pilot through the haptic response, which is the defining characteristic of that type of system as I understand it. All MCAS does is modify the trim, which has the effect of passively modifying the flight characteristics of the aircraft.
>In the 737 Max, like most modern airliners and most modern cars, everything is monitored by computer, if not directly controlled by computer. In many cases, there are no actual mechanical connections (cables, push tubes, hydraulic lines) between the pilot’s controls and the things on the wings, rudder, and so forth that actually make the plane move. And, even where there are mechanical connections, it’s up to the computer to determine if the pilots are engaged in good decision making (that’s the bitey dog again).
As far as I am aware, Boeing has maintained manual reversion with regards to the trim system and yoke in the 737 MAX 8. I.e. there are direct connections to the control surfaces from the pilot's hand actuated controls. Boeing's concession to FBW is by implementing parallel automation managed control circuits that allow for electrically driven manipulation of control surfaces fed back to the pilot through the mechanical linkage. The envelope-protection -> bitey-dog analogy in this case, is still an accurate characterization.
>But it’s also important that the pilots get physical feedback about what is going on. In the old days, when cables connected the pilot’s controls to the flying surfaces, you had to pull up, hard, if the airplane was trimmed to descend. You had to push, hard, if the airplane was trimmed to ascend. With computer oversight there is a loss of natural sense in the controls. In the 737 Max, there is no real “natural feel.”
As far as I can ascertain, there still is "natural feel" in regards to pitch control. There are no hydraulic boosters in place. The problem though, is that MCAS actually hides the aberrant behavior at high AoA from the pilot by intentionally down-trimming the plane. This gets the job done (by some definitions), but does it instead through the trim system (which operates automatically in other circumstances enough where the pilot may mistake the behavior for some other system) and without doing anything to the stick (the primary instinctual control for the plane).
Other than those quibbles, this is a beautiful write-up that is a treat to read. The Supplemental Type Certification section was also informative for me, as it illustrates unambiguously that there was a process to handle this exact type of augmentation which was sidestepped by Boeing for whatever reason.
Bravo!