Originally Posted by
GordonR_Cape
There are two followup aspects to your question, depending on the version of MCAS 1.0 and MCAS 2.0:
- MCAS 1.0 was designed to satisfy the criteria that you describe, though not smoothly, due to the 5 second pause.
- MCAS 2.0 may remove the option of repeated trim during the same high AOA "event", depending on the definition of event. This would not satisfy the 25.173 criteria, if it allowed the pilots to do a second pull into the high AOA region, after interrupting MCAS by blipping the stabiliser trim switches.
Long ago I posted this assertion: It is logically impossible to design a system that satisfies both limited MCAS activation and 25.173 criteria simultaneously. One of the two limits has to be broken in some scenarios, for example pilots repeatedly entering the high AOA condition. I have not seen any evidence to contradict my assertion.
I think everyone is missing the the point of MCAS. MCAS is supposed to operate behind the scenes to add just a little nose down trim at high angles of attack to replicate the "feel" of a "normal" aircraft" as the pilot pulls the nose up
WTHOUT TRIM. FAA 25.173 requires it for nose up, neutral trimmed high angles of attack. It is not needed if the flaps are out or if the autopilot is on. It is also not needed if the pilots decides
to trim on his own.
When MCAS has been triggered at high angles of attack, as soon as the pilot touches the trim, MCAS is disabled because the pilot now has decided to trim for whatever trim feel they want. There is now no need for MCAS as there is no FAA mandated "feel" that needs to be demonstrated. MCAS does not operate for 5 full seconds after each application of trim.
So yes, I believe MCAS can satisfy both limited activation and 25.173 criteria simultaneously.