Originally Posted by
FCeng84
As to the idea of a stick pusher rather than the MCAS use of the horizontal stabilizer, that has been discussed at great length. The 737 does not include the necessary hardware to implement such a stick pusher so the statement that "Surely a fail passive method to apply extra force to the stick is not a difficult thing to do." is not correct.
I know the 737 does not have a stick pusher, but, at least in the NG, it did increase stick power approaching a stall. That seems to be insufficient in the MAX, or not included in its systems. Below an excerpt from the NG FCOM, latest version i flew which is by now a few years old. If i understand it, there is now a fourth system with MCAS to aid in that situation.
Stall identification and control is enhanced by the yaw damper, the Elevator Feel
Shift (EFS) module and the speed trim system. These three systems work together
to help the pilot identify and prevent further movement into a stall condition.
During high AOA operations, the SMYD reduces yaw damper commanded rudder
movement.
The EFS module increases hydraulic system A pressure to the elevator feel and
centering unit during a stall. This increases forward control column force to
approximately four times normal feel pressure. The EFS module is armed
whenever an inhibit condition is not present. Inhibit conditions are: on the ground,
radio altitude less than 100 feet and autopilot engaged. However, if EFS is active
when descending through 100 feet RA, it remains active until AOA is reduced
below approximately stickshaker threshold. There are no flight deck indications
that the system is properly armed or activated.
As airspeed decreases towards stall speed, the speed trim system trims the
stabilizer nose down and enables trim above stickshaker AOA. With this trim
schedule the pilot must pull more aft column to stall the airplane. With the column
aft, the amount of column force increase with the onset of EFS module is more
pronounced.