Hard to keep up gents. Wonder if this description has been posted before. Pity there is no source and date on it.
The MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated AOA. 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.
The MCAS function becomes active when the AOA exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 deg's and are provided at a rate of 0.27 deg's per second. The magnitude of the stabilizer input is lower at high Mach number, and greater at low Mach numbers. The function is reset once the AOA falls below the AOA threshold, or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.