(2)
The landing flap position warning switch is set to actuate at 15 units of flaps, and the takeoff flap position warning switch is set to actuate at 25 units of flaps. The objective of these two switches is to provide a ground to the GPWC for flap settings of less than 25 units. One switch provides ground for settings of 5 to 25 units. The second switch provides coverage for flaps up (0 units) by providing a ground for settings of 5 to 15 units. 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.
(3)
The air/ground relay supplies a binary input to the GPWC. The air/ground input allows the GPWC to inhibit mode functions while the airplane is on the ground to decrease nuisance warnings. When the airplane is in the air, the air/ground input inhibits testing of the GPWC.
D. The GPWC provides ten 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 WINDSHEAR 7 2 WHOOP WHOOP PULL UP 1 and 2 3 TERRAIN 2 4 TOO LOW - TERRAIN 4 5 TOO LOW - GEAR 4A 6 TOO LOW - FLAPS 4B 7 MINIMUMS (WHEN ACTIVATED) 6 8 SINK RATE 1 9 DON'T SINK 3
10 GLIDE SLOPE 5
NOTE: WINDSHEAR aural message is preceded by one cycle of siren sound.
____
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A
737-300/400/500
MAINTENANCE MANUAL
1000
HEIGHT
ABOVE
TERRAIN
(FT)
300
150
50
0
(0.46) (0.7) (1.05)
DOTS "FLY UP" (DEGREES BELOW GS)
1
THE REPEAT TIME OF THE GLIDESLOPE WORD CHANGES AS
THE TERRAIN CLEARANCE AND GS DEV CHANGE
Mode 5 - Excessive Deviation Below Glideslope
Figure 8
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH SUNDSTRAND MK V GPWC ú
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
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.
(2)
Closure Warning (Mode 2)
(a)
With the flaps not in landing configuration (airplane in cruise), the computer will provide the pilots with a warning if the airplane exceeds the terrain closure rates with respect to the terrain clearances shown in Fig. 5, (Mode 2A). The PULL UP indicator and two cycles of aural warning TERRAIN come on. If the airplane remains within the curve boundary, the aural warning will change to PULL UP, repeated every 0.75 seconds. Upon leaving the curve boundary, due to either terrain change or pull up maneuver, the aural warning will change to TERRAIN, repeated every 0.75 seconds. The warning will remain on until the barometric altitude has increased by 300 feet. During high speed operation, the upper curve boundary is increased linearly betweeen 0.35 and 0.45 mach to provide early warning.
(b)
With flaps in the landing configuration, the warning boundary is limited as shown in Fig. 5, (Mode 2B). No altitude gain is required to turn off the TERRAIN aural warning after the PULL UP aural warning is activated. The PULL UP aural warning is inhibited at radio altitude below 700 feet with landing gear down. Only the TERRAIN aural warning is activated.
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