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Section 8 Terrain Awareness Warning System
8-10
IDU-450 EFIS Software Version 8.0H (Rotorcraft)
1
st
Ed Nov 2018
Figure 8-7: Rotorcraft GPWS Mode 2
8.6.
Sink Rate after Takeoff or Missed Approach (GPWS Mode 3)
GPWS Mode 3 function uses aircraft vertical speed information and AGL
altitude to alert when a sink rate is detected immediately after takeoff or
initiation of a missed approach. GPWS Mode 3 is armed by either being in
ground mode or by being on the first leg of a missed approach procedure
(as determined by the GPS/SBAS) with distance to the active runway
threshold increasing. GPWS Mode 3 is disarmed upon climbing through
400 feet
AGL
, traveling more than
3 NM
from the last point at which the
ground definition was satisfied (this is near the liftoff point), or transitioning
to the second leg of a missed approach procedure. GPWS Mode 3 has a
caution threshold based upon height above terrain and vertical speed.
When below the caution threshold (AGL threshold = 1.4 x sink rate), a
GPWS Mode 3 caution is generated.
Figure 8-8: GPWS Mode 3 Warning (Sink Rate after Takeoff or
Missed Approach)
0
200
400
600
800
1000
1200
1400
0
2000
4000
6000
8000
Height Above
Terrain
(ft.)
Terrain Closure Rate (fpm)
Rotorcraft Mode 2
2A Envelope
2A Speed Expansion
2B Envelope