C.  
Stall warning computer No. 2 controls the first officer's control column shaker. Computer No. 2 is powered by 28 volts dc and 115 volts ac through circuit breakers on the P6-1 panel from the electronics No. 2 bus. Inputs to computer No. 2 come from the following sources:

 (1)  
Right AOA sensor

 (2)  
Left flap position transmitter

 (3)  
N1 and N1 valid tachometer indicator for engine No. 2

 (4)  
N2 tachometer indicator for engine No. 1

 (5)  
Air/ground relays on E-11 shelf

 (6)  
Leading edge light module

 (7)  
Right digital air data computer (DADC 2) on ARINC 429 bus

 (8)  
STALL WARNING TEST NO. 2 switch on P5-18 module

 D.  
Several different airplane flight conditions can cause the stall warning computer to activate the control column shaker. The shaker will be activated by whichever condition gives the earliest warning of an approaching stall.

 (1)  
Normal Stall Warning

 (a)  
The control column shaker is activated when airplane angle of attack becomes too great. The specific angle of attack at which the shaker is activated depends on flap position.

 (2)  
Asymmetry Stall Warning

 (a)  
If the leading edge flaps and slats are not in the position corresponding to that of the trailing edge flaps, the angle of attack required to activate the shaker will be lowered. The amount by which it is lowered depends on flap position.

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH DIGITAL STALL WARNING ú

 27-32-00
 COMPUTER P/N 65-52819  ú CONFIG 1 ú 01 Page 5 ú Mar 15/90
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 (3)  
High Thrust Stall Warning

 (a)  
The high thrust stall warning is enabled when the N2 tachometer for the opposite engine reads greater than 75%. Under this condition, the angle of attack required to activate the shaker will be lowered. The amount by which it is lowered depends on flap position and the coefficient of thrust gradient (CTG). The stall warning computer calculates the CTG from airspeed and the N1 tachometer for the near engine.

 (4)  
Speed Floor Stall Warning

 (a)  
The stall warning computer will activate the shaker if the airplane airspeed falls below a reference speed for a given flap position (Table I).

 FLAP SETTING  MINIMUM AIRSPEED (KNOTS)
 40 90 30 90 25 95 15 100 10 100 5 105 2 105 1 110
 TABLE I
 E. Stall Warning Mode Failure Schedule
 (1)  
If a failure of the high thrust stall warning is detected by the computer, the other modes (normal, asymmetry, or speed floor) will not be affected. If a failure of the normal mode is detected, the speed floor mode will not be affected. If failures of both normal and speed floor modes are detected, shaker operation will be inhibited.

 F.
Digital Stall Warning Computer Outputs

 (1)  
In addition to activating the control column shaker, the stall warning computer provides information to other airplane flight systems.

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH DIGITAL STALL WARNING ú

 27-32-00
 COMPUTER P/N 65-52819  ú CONFIG 1 ú 05 Page 6 ú Nov 15/90
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 (2)  
Digital Flight Data Acquisition Unit (Airplanes with DFDAU)

 G.
BITE

 (1)  
The stall warning computer has internal built-in test equipment (BITE) for maintenance and testing purposes. The front panel of the computer has a START BITE switch and LED indicator lights.

 (2)  
To perform a BITE test, press the START BITE switch for two seconds. All lights on the computer will come on for two seconds to confirm that the lights are functional. A light which stays on after two seconds indicates a fault with the unit called out by that light's label. The fault light will go off after 25 seconds.

 (3)  
　
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