B-18 Page 18 of 22
MN-FLT-OH-201
Flight Crew Operations Manual Bulletin No. GOT-18 , Dated March 1, 2021 (continued)
Stall Identification
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 Stall Management/Yaw Damper (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 approximately doubles control column forces.
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 stick shaker threshold.
There are no flight deck indications that the system is properly armed or
activated.
As airspeed decreases towards stall speed with flaps down, the Speed Trim
System uses the Speed Trim function to trim the stabilizer nose down above stick
shaker AOA. With flaps up, as AOA approaches stick shaker, the stabilizer nose
down trim commands transition from the Speed Trim function to the MCAS
function. These trim schedules produce a predictable and increasing column
force with increasing aft column displacement. With the column aft, the amount
of column force increase is more pronounced with the onset of EFS.
March 1, 2021
