Quote:
Originally Posted by Fuzz
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I would assume autopilot takes care of the aircraft pitch itself, so it wouldn't need MCAS. "Manual mode" is not taking it out of autopilot in this case, it is overriding the MCAS system. They are 2 separate "auto" settings, where MCAS 's only job is to prevent runaway pitch. Autopilot is much more than that.
That's how I understand it, anyway.
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MCAS’ purpose is actually to use trim to pitch the nose down in a nose high approach to stall situation. (With autopilot off and flaps up). The problem is it trimming down due to a malfunction when it shouldn’t be. To stop it the crew needs to flip the stab trim cutout switches.
In the lion air accident it was a malfunctioning angle of attack sensor that caused the crew to be hand flying, and that erroneous sensor told the MCAS that it was approaching a stall causing it to trim down to prevent the aerodynamic stall. Which of course was incorrect.
The purpose of the system is fine, but obviously it appears that it was poorly designed.