[Ref ACE The Technical Pilot Interview 152/348]
The GPWS (Ground proximity warning system) is mandatory required for public transport aircraft over 5700 kg. It is a important system provide two major functions: 1) alert and 2) warning system.
After reaching certain precomputerized active range, a central computer will then activate aural and visual alerts to warn the flight crew by using the following cockpit equipment:
- Speakers – “Pull Up“
- a pair of red warning lights with “Pull Up.”
- inhibited amber (marker) advisory light (in a glide slope deviation)
The GPWS receives various data inputs (configuration, height/ altitude, and check if there is instrument landing system (ILS) glide slope deviation). It then calculates these inputs to detect if any of the potential dangerous:
- Excessive descent rate
- terrain closure
- Height loss after takeoff
- Flaps or gear not selected for landing
- Too low on the ILS glide slope
- Descending below approach minima
When (if) more than one alert or warning is triggered at the same time, the GPWS will give only the highest-priority alert or warning that has been triggered.