27-31-00  STALL WARNING AND PROTECTION SYSTEM Back

A. System Function

The stall warning and protection system (the system) gives the flight crew warnings when the aircraft is near, or at, a stall condition. When the aircraft is at a stall condition, the stick pusher moves the elevators down eight degrees ±0.5 degree. This is from the elevator zero degrees position.

B. System Components (Ref. Fig. 1 thru Fig. 8)

The primary components of the system are the:

• Two Angle-of-Attack (AOA) sensors
• Two signal processors
• Two stick shakers
• Stick pusher

C. System Operation

1. Each AOA sensor gives an output to each signal processor. The signal processors compare the outputs from the AOA sensors with set values and give an output (as applicable).
2. Each signal processor also compares the signals from the left and the right AOA sensors with each other. The signal processors give a warning if they are not in the limits.
3. When the aircraft is near a stall condition, the related signal processor gives outputs to the relate stick shaker. This gives a warning to tell the flight crew and condition of the aircraft.
4. When the aircraft is at a stall condition ,the signal processors give outputs to the :
   • Two stick shakers
   • Stick pusher
   • Red L STALL and R STALL captions, on the Coaming Panel (Ref. 31-51-00)