Originally Posted by
xetroV
Boeing seems to think differently, judging from the Runaway Stabilizer checklist, which includes the following additional step after switching off the cutout switches: "If the runaway continues: stabilizer trim wheel - grasp and hold".
That statement isn't there for "erroneous MCAS". If the MCAS has "gone crazy" due to either faulty inputs and/or internal fault in whatever box drives it, then you can assume that the stab drive itself is healthy and just getting nonsense commands. So the cut-out switches will work.
the "if it still moves" is to cover something like a fault downstream of the cutout switches - maybe a short in the motor driving it regardless of command. In such a failure case, the motor will run regardless of the cutouts, so hanging on to the wheel is the last resort.
The chances of having a simultaneous MCAS (or other command system) fault AND an internal stab motor fault are insanely remote.
The procedure isn't just for MCAS, it has to cover all the various uncommanded stab scenarios.