(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 gears down. Only the TERRAIN aural warning is activated.
(c)
To provide additional nuisance warning protection at the runway threshold during steeper approaches, the lower limit of mode 2B varies as a function of barometric rate as shown in Fig. 5.
(d)
The GPWC cannot provide a warning if an airplane is flying directly towards a vertical cliff with no initial terrain slope at the bottom. Mode 2 warnings are inhibited below 50 feet of radio altitude.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
25002000
1500
HEIGHT
ABOVE
TERRAIN
(FT) 1000
500
500
00.1 0.2 0.3 0.4 0.5 0.6 0.7
MACH NUMBER
MODE 4A
2500
2000
1500
HEIGHT
ABOVE
TERRAIN
(FT) 1000
500
200
500
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
MACH NUMBER
MODE 4B
Mode 4 - Proximity to TerrainFigure 7
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A 737-300/400/500MAINTENANCE MANUAL
1.32.0 3.0
(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
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A 737-300/400/500MAINTENANCE MANUAL
PUSH
WHOOP! WHOOP! PULL UP!
WHOOP! WHOOP! PULL UP!
(7 TIMES TOTAL)
Ground Proximity Warning System - Self Test
Figure 9 (Sheet 1)
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù.
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INHIBIT SWITCH ú ú 05 Page 15 ú Mar 15/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
PUSH
WHOOP! WHOOP! PULL UP!
(7 TIMES TOTAL)
Ground Proximity Warning System - Self Test
Figure 9 (Sheet 2)
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