The AN/MSN-3: An Automatic Ground-Controlled Approach System

A system is described whereby information gathered by a standard ground controlled approach (GCA) radar is utilized to compute automatically all GCA approach-control commands; these commands are then transmitted simultaneously to a maximum of six aircraft via the USAF frequency-division digital data link for automatic control of the aircraft approach. The system is designed to enable continuous human monitoring of the AGCA traffic-control operation and to include visual and aural warning signals in the monitoring system for added safety. Problems relating to optimum system response and gain parameters are discussed and control equations are defined. Results of extensive testing demonstrate a system capable of providing smooth control during the aircraft final approach under high-density traffic conditions. System accuracy is well within specified limits of ±50 feet in azimuth and ±30 feet in elevation at a minimum release point 100 feet above the runway.