B737 Manoeuvre Speed
Derfred
Direct quote from 737 NG FCOM.
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 s shaker. Either stick shaker vibrates both columns through column interconnects.
( With thanks to Boeing )
Hope that helps.