Originally Posted by
Avionista
I believe the JATR report recommended that the 'bare airframe' (i.e.with no MCAS) should be air tested for longitudanal stability. This suggests to me that they are not wholly convinced by the reasons given by Boeing as to why MCAS was needed in the first place. Could it be that not only does the stick force become lighter at a high AoA but, even if the stick back force is reduced/released, aerodynamic forces on the forward positioned engine nacelles at high AoA continue to pitch the nose of the aircraft up into a stall?
Here's the most directly-relevant recommendation from the JATR report:
Recommendation R3.4: The FAA should review the natural (bare airframe) stalling characteristics of the B737 MAX to determine if unsafe characteristics exist. If unsafe characteristics exist, the design of the speed trim system (STS)/MCAS/elevator feel shift (EFS) should be reviewed for acceptability.
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.
Finding F3.4-A: The acceptability of the natural stalling characteristics of the aircraft should form the basis for the design and certification of augmentation functions such as EFS and STS (including MCAS) that are used in support of meeting 14 CFR part 25, subpart B requirements