An altitude alert system gives an aural and visual indication if approaching a selected altitude (acquisition) or departing a selected altitude (deviation). An altitude and the appropriate baro setting can be selected on the altitude alert control panel. The captain’s altimeter/alticoder set provides altitude information based on 1013 mb, which is compared with selected altitude.
The altitude alert warning light will illuminate steady between 900 ft and 300 ft above or below the selected altitude when approaching the selected altitude. The light will flash warning between 300 ft and 900 ft above or below the selected altitude when deviating from the selected altitude. A two second aural warning will sound 900 ft from the selected altitude for acquisition and 300 ft from the selected altitude for deviation. The altitude alert controller is reset to the acquisition mode either by manually depressing
the altitude setting selector or automatically after departing 900 ft from the previously selected altitude. The deviation mode is deactivated with flaps 40° or 50° extended.