Originally Posted by
MPN11
It trims the horizontal stabiliser. Endlessly, unless stopped!
No, not endlessly, and that is a very important distinction. It does it in increments, and only starts a new increment when reset, e. g. by pilot electrical trim input.
This is so important because it is the qualitative difference separating it from "runaway trim".
And you can't
stop MCAS in any normal normal sense. You can only temporarily inhibit it by using manual electric trim, or you can disable electric trim altogether, and that includes disabling the speed trim system, Mach trim and pilot-commanded electric trim. Only crank-and-pulley mechanical trim remains operational.
Bernd