CLOSURE RATE (FPM)
MODE 2B - FLAPS IN LANDING CONFIGURATIONMode 2 - Excessive Closure RateFigure 5

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 (3)  The VHF navigation system provides glide slope deviation signal which is used in the mode 5 computation. The glide slope deviation signal provides a low level input with a sensitivity of 75 mv/deviation dot.
 C.  Binary inputs to the GPWC consist of a landing gear and landing flap position signal and 28-volt dc radio altimeter valid, glide slope valid and baro rate computer valid signals.
 (1)  
The landing gear lever switch actuation is determined by the position of the landing gear control lever. When the lever is moved to the down detent position, the microswitch is actuated. Switch actuation provides a ground to the ground proximity warning system, indicating that the landing gear lever is in the down position. The ground from the landing gear lever switch is also provided to the landing gear accessory module.

 (2)  
The landing flap position warning switch is set to actuate at 15 degrees of flaps, and the takeoff flap position warning switch is set to actuate at 25 degrees of flaps. The objective of these two switches is to provide a ground to the GPWC for flap settings of less than 25 degrees. One switch provides ground for settings of 1 to 25 degrees. The second switch provides coverage for flaps up (0 degrees) by providing a ground for settings of 1 to 15 degrees. With either switch closed, a ground is provided to the ground proximity warning computer, arming the TOO LOW-FLAPS warning. When the flaps are in a landing configuration, both switches are open and the warning is inhibited.

 D.  The GPWC provides nine different voice messages. With the possibility of more than one warning occuring at the same time, the following priority has been established with the associated modes. The highest priority message is always provided. If a higher priority warning occurs, the message will immediately switch to the higher priority message. If a higher priority warning stops, the priority message will complete before switching to any lower priority message.
 Priority________ Message_______  Mode
 1 WHOOP WHOOP PULL UP 1 and 2 2 TERRAIN 2 3 TOO LOW - TERRAIN 4 4 TOO LOW - GEAR 4A 5 TOO LOW - FLAPS 4B 6 MINIMUM (NOT USED) 6 7 SINK RATE 1 8 DON'T SINK 3 9 GLIDE SLOPE 5
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1000 
HEIGHT ABOVE TERRAIN (FT)  500 
100

BARO ALTITUDE (FT) (ALTITUDE LOSS)
Mode 3 - Descent After Takeoff
Figure 6

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 E.  The GPWC processes the input signals to provide warning outputs during the following flight conditions:
 (1)  
Excessive Sink Rate Warning (Mode 1)

 (a)  
The computer provides the pilots with a warning if the airplane exceeds the barometric sink rate with respect to terrain clearance as shown in Fig. 4. The warning may be visual and audible and is continuous while the airplane is within the warning area. The aural warning is SINK RATE, and is repeated every 0.75 seconds.

 (b)  
The aural warning changes to PULL UP if the airplane sink rate continuous and penetrate the warning area as shown in Fig. 4. The PULL UP warning boundary is below the SINK RATE warning boundary.