CDA with RTA in a mixed environment

Procedures for continuous descent approach (CDA) and optimized profile descents (OPD) are being fielded to allow aircraft to approach moderately dense terminal areas while flying efficient, near-idle descent trajectories that save fuel, and reduce emissions and noise. However, CDA operations can have a negative impact on the airspace throughput and controller workload. Air traffic management automation systems are being developed and fielded to assist controllers in handling more aircraft and larger airspace per controller. Many of these systems are time-based and built to predict the aircraft trajectories as accurately as possible. Three technologies that can assist ATM automation systems in enabling CDA operations in dense terminal areas while maintaining or increasing airspace throughput and safety: controller pilot data-link communications (CPDLC), automatic dependent surveillance contract, extended projected profile (ADS-C EPP), required time-of-arrival control (RTA). Initial trials using RTA capability have shown some challenges in integrating RTA and non-RTA aircraft due to the structural shape of the speed profile strategy (how the speeds are chosen in different flight segments), and the automatic speed adjustments made by the RTA algorithm in response to observed trajectory error. Both of these issues can reduce the relative spacing between aircraft in trail. This paper presents an operational concept for how the RTA capability can enable the use of CDA procedures in high density traffic in a mixed equipage environment, either with or without the use of digital data link.