Ground proximity warning instrument using flight path modulation of glide slope alerting function

Abstract From the Canadian patent

A ground proximity warning system monitors the flight path angle (78) or barometric or inertially derived descent rate (74) of the aircraft and modulates the glide slope alerting function (80) in accordance with flight path angle (78) or descent rate (74) when the aircraft is not descending rapidly even though it is below the glide slope in order to reduce nuisance warnings without compromising system sensitivity. Alternatively the repetition rate of, the alert may be varied as a function of the flight path angle (78) or descent rate (74) to provide less frequent alerts when the aircraft is not descending rapidly.