Alarm filtering in a ground proximity warning system

Abstract

A ground proximity warning system used by aircraft when unsafe flight configurations defined by specified flight warning mode envelopes are detected. The invention provides that alarm generation signals are not immediately given, but instead the continuing flight of the aircraft is monitored by an alarm filtering system. The filtering system uses independently variable maximum and minimum threshold levels, and filtering constants which can be incremented and or decremented as functions of the flight location of the aircraft and the specific warning mode envelope for suppressing false or unnecessary alarm generation. The filtering parameters may be varied independently for each flight warning mode. In addition, a priority-ordered series of audio warnings are provided so that warnings once started are completed in the absence of higher priority warnings, even if the warning conditions cease to exist. Low priority warnings which are interrupted by higher priority warnings are regenerated when the higher priority warnings have been completed.