737 MAX Flight Crew Operations Manual
Warning Systems -
System Description
MN-FLT-OH-201
15.20.7
When either an overspeed condition or a system test occurs, the ADIRU transmits
a signal to the aural warning module, sounding the clacker. The system can only
be tested on the ground.
Stall Warning System
Natural stall warning (buffet) usually occurs at a speed prior to stall. In some
configurations the margin between stall and natural stall warning is less than
desired. Therefore, an artificial stall warning device, a stick shaker, is used to
provide the required warning.
The stall warning “stick shaker” consists of two eccentric weight motors, one on
each control column. They are designed to alert the pilots before a stall develops.
The warning is given by vibrating both control columns. The system is armed in
flight at all times. The system is deactivated on the ground.
Two independent, identical stall management yaw damper (SMYD) computers
determine when stall warning is required based upon:
• alpha vane angle of attack outputs
• ADIRU outputs
• anti–ice controls
• wing configurations
• air/ground sensing
• thrust
• FMC outputs.
The SMYD computers provide outputs for all stall warning to include stick shaker
and signals to the pitch limit indicator and airspeed displays and the GPWS
windshear detection and alert.
Two test switches are installed in the aft overhead panel. Pushing either of these
initiates a self–test of the respective stall warning channel. The No.1 activates the
Captain stick shaker, and the No. 2 activates the F/O stick shaker. Either stick
shaker vibrates both columns through column interconnects.
Autoland Advisory Messages
1B785, 1J585 - 1J594
(as installed)
When a system failure is detected that affects autoland status, an advisory message
is displayed on the engine display. Two advisories, NO LAND 3 and NO
AUTOLAND, are available. Only one advisory message can be displayed at one
time. A cancel/recall switch, located on the MFD panel, controls the display and
recall of the advisory messages.
October 26, 2021
