This paper describes a system that calculates aircraft visual range with instrumentation alone. A unique message is
encoded using modified binary phase shift keying and continuously flashed at high speed by ALSF-II runway approach
lights. The message is sampled at 400 frames per second by an aircraft borne high-speed camera. The encoding is
designed to avoid visible flicker and minimize frame rate. Instrument qualified visual range is identified as the largest
distance at which the aircraft system can acquire and verify the correct, runway-specific signal. Scaled testing indicates
that if the system were implemented on one full ALSF-II fixture, instrument qualified range could be established at 5
miles in clear weather conditions.