The function is reset once angle of attack falls below the Angle of Attack 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.
To summarise; MCAS will trim the Stabilizer down for up to 9.26 seconds (2.5 deg nose down) and pause for 5 seconds and repeat if the conditions (high angle of attack, flaps up and autopilot disengaged) continue to be met. MCAS will turn the trim wheel. Using electric pitch trim will only pause MCAS for 5s; to deactivate it you need to switch off the STAB TRIM CUTOUT switches.
Air speed, attitude, altitude, vertical speed, heading and engine power settings are the primary parameters the flight crews use to safely operate the airplane in normal flight. Stick shaker and the pitch limit indicator are the primary features used for the operation of the airplane at elevated angles of attack. All recommended pilot actions, checklists, and training are based upon these primary indicators. Neither the angle of attack indicator nor the AOA Disagree alert are necessary for the safe operation of the airplane. They provide supplemental information only, and have never been considered safety features on commercial jet transport airplanes.
Boeing is issuing a display system software update, to implement the AOA Disagree alert as a standard, standalone feature before the MAX returns to service. When the MAX returns to service, all MAX production aircraft will have an activated and operable AOA Disagree alert and an optional angle of attack indicator. All customers with previously delivered MAX airplanes will have the ability to activate the AOA Disagree alert."
Following the Lion Air accident, on 7 Nov 2018 the FAA issued an Emergency AD (2018-23-51) and Boeing issue an Ops Manual Bulletin (TBC-19) for MAX Runaway Stabilizer procedure directing operators to existing flight crew procedures" to address circumstances involving erroneous angle-of-attack sensor information. 2b1af7f3a8