Tactical Conflict Detection with Altitude Restrictions in Terminal Airspace

Abstract

Automated conflict detection in terminal airspace is a challenging problem, in part because key information regarding flight intent is not available. Unlike en route controllers, terminal controllers currently do not enter altitude clearances when they issue them by voice, so the altitude at which a flight will level off is unavailable to the conflict detection automation. This uncertainty increases the likelihood of false alerts. Requiring terminal controllers to make entry of altitude clearances may be met with resistance due to workload concerns. A new method is studied in which a ground-based trajectory predictor predicts altitude leveloffs a priori, based on altitude restrictions on published runway descent profiles and at waypoints on Nominal Interior Routes (NIRs) and Area Navigation (RNAV) Departure Procedures (DPs). The full benefit of the intent information of all altitude clearances is shown to be achievable when controllers only make entry of altitude clearances not attributable to altitude restrictions, which leads to an insignificant workload increase; an unacceptable level of workload increase may result if all altitude clearances are entered during busy hours. In addition, the integration of altitude restriction increases the average alert lead time to 43 seconds from 37 seconds without. 2 The inherent complexities of terminal operations pose a number of challenges in the development of automated tools that alert air traffic controllers to potential conflicts. Routine large-angle turns without well-defined intent information before final approaches requires proper handling to prevent a proliferation of nuisance alerts: alerts that do not provide useful information beyond what the controllers know and are not necessary to maintain safety [1]. Spacing of aircraft near standard separation thresholds to maximize arrival and departure throughput increases the difficulty of predicting separation conflicts without causing false alerts: alerts on predicted losses of separation that do not materialize, with no indication of any controller or pilot intervention [2]. The difficulty also stems from the dynamic and complex nature of the standard separation criteria, which depend on relative course, aircraft weight classes, distance to the runway, and other factors [3]. The Common Automated Radar Terminal System (CARTS) [4], which has been operational since the 1980s, and the recent Standard Terminal Automation Replacement System (STARS) [5] have a Conflict Alert (CA) functionalitythat generates safety alerts when CA determines that two aircraft are in dangerous proximity to one another or are on a course that will put them in dangerous proximity to one another. The Federal Aviation Administration (FAA) analyzed CA performance and classified 80% of CA alerts in terminal airspace as nuisance [1,6]. The analysis suggested flight-intent information to be incorporated in conflict detection algorithms so the nuisance alerts may be reduced.A ground-based initial prototype system that incorporates flight intent inform...

Enabling Airspace Integration for High-Density On-Demand Mobility Operations

“…40 NASA's Small Aircraft Transportation System (SATS) project successfully flight tested an automated, centralized sequencing and scheduling algorithm that could be extended to ODM operations. 41 Tactical conflicts between aircraft using the same TOLA could be managed by cooperative or centralized algorithms modeled after approaches being tested for busy IFR terminal areas, 42,43,44,45,46,47,48 however these algorithms are designed to assist an air traffic controller in the traditional ATM system. The concepts of operation of these algorithms could be adapted so that the SSS and separation approaches for ODM require no human oversight and can operate in a fully automatic mode.…”