Originally Posted by
Halfnut
10
MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall. MCAS is activated without pilot input and only operates in manual, flaps up flight. The system is designed to allow the flight crew to use column trim switch or stabilizer aislestand cutout switches to override MCAS input. The function is commanded by the Flight Control computer using input data from sensors and other airplane systems.
Wow, thanks for posting. This appears to be the missing puzzle piece, a new MAX system apparently unknown outside of Boeing which directly links AoA to the stab for improved stall protection (when sensors are working). I can't see how MCAS can be retained in the present form, with a single high alpha AoA sensor failure now capable of failing the MCAS to inappropriate downtrim as well as providing a set of additional cascading alarming failures (primarily UAS) to reduce the pilot's chances of recognising the problem in time and deactivating trim. I do still wonder whether the STS did not contribute to the accident at all, or whether in UAS it made things worse by adding inappropriate trim input to the MCAS's.