Mixing four-dimensional equipped and unequipped aircraft in the terminal area

The problem of mixing four-dimensional (4-D) equipped aircraft (aircraft equipped with onboard guidance systems that can predict and control the touchdown time of an aircraft to an accuracy of a few seconds throughout the descent) with unequipped aircraft in the terminal area has been investigated via a real-time air traffic control simulation study. The objective of this study was to develop scheduling algorithms and operational procedures for various traffic mixes that ranged from 25 to 15% 4-D equipped aircraft. Results indicate substantial reduction in controller workload and an increase in orderliness when more than 25% of the aircraft are 4-D equipped. Moreover, this is accomplished without increasing the workload or adding delays for the unequipped aircraft.