A Flush-Mounted Glide-Path System

An instrument-landing system glide-path has been developed which produces a straight-line path originating directly from the touchdown region on the runway. This system makes use of five flush-mounted runway antennas which are mounted directly in the runway, thus eliminating the ground-reflected signals which are presently used to form the path. As a result, the effects of terrain irregularities in the approach region are minimized. Additional benefits realized in flush-mounting the glide-path system are the elimination of parallax problems encountered by flight close in, and the elimination of hazards of antenna supporting masts and buildings near the runway. Potential use of the glide-path at low elevations is enhanced by the paralleling of the path limits during the last 600 feet of the flight path. The path limits cease to converge and maintain a constant value which provides tolerance especially necessary for pilot-controlled flights, while still maintaining sufficient margin of safety. This new glide-path system is completely compatible with the present airborne equipment, and only a minor addition to the transmatter need be made. Automatic servo monitoring is provided for maximum stability in addition to conventional fail-safe monitoring.