The GPWS generates the following sound signal or signals when the helicopter is sinking after a take-off or a go-around…
Refer to figure.
The Ground Proximity Warning System (GPWS) or the Enhanced GPWS (EGPWS) is now a required equipment that improves safety and provides numerous protections that prevent Controlled Flight Into Terrain (CFIT).
GPWS provides by means of distinctive audible signals, which may be supplemented by visual signals.
There is a distinction between the more and less urgent warnings, by calling the less urgent "ALERT" and the more urgent "WARNING". The alert requires only a corrective response, while a warning requires an immediate climb manoeuvre.
The following GPWS modes do not use the TAWS database and are common to most GPWS systems:
| Mode | Meaning | Initial Audio Alert | Second Audio Warning |
| Mode 1 | Excessive descent rate | “SINK RATE” (twice) | “PULL UP” (twice) |
| Mode 2 | Excessive terrain closure rate (inhibited during autorotation or when the low altitude switch is selecteed) | “TERRAIN” (twice) | “PULL UP” (twice) |
| Mode 3 | Altitude loss immediately after take-off or missed approach (go around) (when it loses 10% of altitude with landing gear not in landing configuration or speed is greater than 50 kt) | "DON`T SINK" (twice) | NONE |
| Mode 4 | Insufficient terrain clearance related to phase of flight, altitude, speed and configuration. There three different envelopes (4A, 4B, 4C). | “TOO LOW, GEAR,” “TOO LOW, TERRAIN” | NONE |
| Mode 5 | Glideslope deviation | “GLIDESLOPE” (twice, initially at half volume) | “GLIDESLOPE, GLIDESLOPE” (at full volume) |
| Mode 6a | When passing the decision height | “MINIMUMS” "ALTITUDE" | NONE |
| Mode 6b | Excessive bank angle | “BANK ANGLE” (twice) | NONE |
| Mode 6c | Tail Strike Warning | “TAIL TOO LOW” (depending on radio altitude, pitch attitude, pitch rate, baro altitude rate) | NONE |
NOTE:
- On some helicopters, the aural alerts are preceded by a "WHOOP WHOOP" noise.
- Mode 6 gives audio alert only.
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