Design of a Control Law for an Autonomous Approach and Landing Spacing System

One of the flow bottlenecks in the National Airspace System is the landing runway. Flights are at their lowest speed for the approach and landing phase, and must be sequenced in close proximity to maximize use of the runway but with enough separation to avoid a wake vortex encounter. Self-separation, Required-Time-of-Arrival and other technologies have reduced the excess separation between flights that contributes to decreased runway throughput. A critical parameter in these technologies is the excess spacing buffer, over and above the required wake vortex separation distance, that is required to account for stochastic phenomena that affect separation in the approach such as atmospheric conditions, ATC instruction execution delays, and aircraft performance. This paper describes a closedloop control law to autonomously calculate and adapt the excess spacing buffer in real-time to achieve the desired level of safety while maintaining maximum throughput.