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Section 8 Terrain Awareness Warning System
8-12
IDU-450 EFIS Software Version 8.0H (Rotorcraft)
1
st
Ed Nov 2018
Table 8-9: HTAWS GPWS Mode 4A Envelopes
Segment Speed
(KIAS)
AGL Altitude (ft
.
)
4A Low-Speed
100
150
400 in autorotation
4A High-Speed
100
Figure 8-10: Rotorcraft GPWS Mode 4
8.8.
Excessive Downward Deviation from an ILS Glideslope
(GPWS Mode 5)
GPWS Mode 5 function is present in Enhanced HTAWS only and uses ILS
glideslope deviation information and AGL altitude to alert when an
excessive downward glideslope deviation is detected on the final approach
segment of an ILS approach. GPWS Mode 5 is armed when a valid
glideslope signal is being received, and the aircraft is below
1000’ AGL
.
GPWS Mode 5 has a caution and warning threshold. When below a
threshold, a GPWS Mode 5 warning is generated. The curve compares
glideslope deviation to AGL altitude.
0
200
400
600
0
100
200
300
Height Above
Terrain
(FT)
Airspeed (Knots)
Rotorcraft Mode 4
Normal
Autorotation