Originally Posted by
EDML
...So far we where told that MCAS was initially designed to work only at very low speeds. Later on, during test flights, they discovered they also need it at higher airspeeds with even more authority....
It was the other way round. From the JATR report:
Observation O3.4-A: The original implementation of MCAS was driven primarily by its ability to provide the B737 MAX with FAA-compliant flight characteristics at high speed. An unaugmented design would have been at risk of not meeting 14 CFR part 25 maneuvering characteristics requirements due to aerodynamics.
Observation O3.4-B: Extension of MCAS to the low-speed and 1g environment during the flight program was due to unacceptable stall characteristics with STS only. The possibility of a pitch-up tendency during approach to stall was identified for the flaps-up configuration prior to the implementation of MCAS.
https://www.faa.gov/news/media/attac...A_Oct_2019.pdf
One of the many scary parts here: the tech pilots were left in the dark by the test pilots and aero developers a mere four month before certification. So they knew of the high speed / limited authority implementation, but apparently were surprised by the later low airspeed high authority part. Sounds like the left hand had no clue what the right hand was doing...
A hectic last minute change to cover for an airframe instability, with dire consequences. As Tomaskî said, the interesting part is how this alarming discovery from 2016 was followed-up, and how a real review of this was avoided (until two years and a crash later).