If you grip the control column, there's a switch toggle with 3 push-to-hold positions under your thumb. Nose up, off, nose down. It directly turns on the stabilizer trim motor, overriding any other signal.
When you put in trim with this switch, there is a wheel, about 18 inches across, right next to the pilot that starts to turn. As long as you give input, the wheel turns.
It is not quiet. It is a mechanical device.
Push trim for a 1/2 second, the wheel turns a bit.
Autopilot puts in trim, the wheel turns.
MCAS puts in trim, the wheel turns.
This is a very obvious and continuous source of information to the pilot that the stab trim is changing.
Technically it (used to) reset the timer until MCAS activation to 5 seconds after it is released. So you'd have to repeatedly engage to get your stabilizer to where you want it and cut the power. They removed the ability for the electric switches to actuate while the FC was isolated from the stabilizer motor controls as part of the MAX design. With NG's you could flip one cutout switch which would isolate the computer, while leaving on the yoke switches. In MAX, flipping either one apparently cuts out both the computer and the switches.
> So you'd have to repeatedly engage to get your stabilizer to where you want it and cut the power.
No. The electric trim switches override the MCAS signal (in addition to resetting the timer). You can just hold them on until the trim is normal. This is indeed what both the LA and EA crews did repeatedly, they just did not then turn off the stab trim.
This procedure is detailed in the Emergency Airworthiness Directive sent to all MAX pilots after the first crash.
Boeing Emergency Airworthiness Directive
"Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT."
The pickle switch overrides the MCAS command, meaning it can be used to restore normal trim. Then, the trim system can be turned off via the console cutoff switches.
No MCAS is not active with autopilot, because it's not needed. MCAS is there in manual flight to give the human pilot a specific "feel" to the control column forces at high angles of attack. Autopilot doesn't need that.
What does the switch do? I have scanned a few articles about this by now, and none of them describe it's purpose or function. Does it turn off MCAS?