Autonomous precision approach and landing system APALS

The autonomous precision approach and landing system (APALS) system is a precision approach and landing system designed to enable low-visibility landings at many more airports than is now possible. It is an autonomous navigation system which uses standard avionics equipment to determine the aircraft position and altitude with respect to unique terrain features over which the aircraft flies. The primary measurement is made with the aircraft´s weather radar and provides the range and range rate information necessary to update the precision navigation system. The system makes use of stored terrain map data as references for map matching with synthetic aperture radar (SAR) maps. A flight simulation lest program which evaluated the ability of pilots to land in low-visibility conditions was conducted. The results are summarized