Definition
A cockpit switch that allows the flight crew to suppress the terrain alerting and warning functions of a Ground Proximity Warning System (GPWS) or Terrain Awareness and Warning System (TAWS). When activated, it prevents the system from generating terrain-related aural and visual alerts during phases of flight where those alerts would otherwise be triggered by intentional operations near the ground.
Plain English
A switch the pilot can use to turn off the system that warns about terrain getting too close. It is used when the aircraft is intentionally operating near the ground and the warnings would otherwise sound continuously.
Context Anchor
Seen in aircraft equipped with terrain-warning equipment, usually on the instrument panel, avionics panel, or in checklist procedures.
Derivation
Inhibit comes from the Latin inhibere, meaning to hold back or restrain. The switch holds back the terrain warning system from doing what it would normally do.
Why Pilots Care
Lets pilots suppress repeated false alerts at airports surrounded by mountains or during steep approaches without losing the overall safety benefit of the system once the switch is turned off again.
Intuition Check
Inhibit does not mean the terrain system has failed. It means the pilot has selected a switch that prevents that terrain-warning function from alerting.
Example Sentence 1
Before commencing the circling approach into the unpublished strip, the captain selected the terrain inhibit switch to prevent nuisance GPWS alerts.
Example Sentence 2
After clearing the ridge line the crew turned the terrain inhibit switch off to restore full protection for the remainder of the flight.