Time scheduling of a mix of 4D equipped and unequipped aircraft

In planning for a future air-traffic system that is to be extensively automated, it is necessary to confront the transition situation in which some percentage of the traffic must be handled by conventional means. A safe, efficient transition system is needed since initially not all aircraft will be able to respond to a more automated system, and since it is necessary to encourage users of the system to purchase the equipment required for the more automated operation. The specific problem addressed in this paper is that of time-scheduling a mix of 4D equipped aircraft (aircraft that can accurately meet a controllerspecified time-schedule at selected way points in the terminal area) when operating in conjunction with unequipped aircraft (aircraft that require air-traffic handling by means of standard vectoring techniques). First, a relationship between time-separation and system capacity is developed. The conditions under which a mix of traffic can lead to a capacity improvement have previously been derived. The time-separations are then incorporated into a set of scheduling algorithms which contain the required elements of flexibility needed for terminal-area operation, such as delaying aircraft and changing time-separations. The problem of reducing the size of time-separations allotted for vectored aircraft by means of computer assists to the controller is also addressed.