This paper presents a process for selecting candidate Detect-and-Avoid Well Clear definitions for Unmanned Aircraft Systems and non-cooperative aircraft. The selection is based on considerations of the unmitigated collision risk, maneuver initiation range, and others. Operational assumptions related to low cost, size, weight, and power sensors equipped by the Unmanned Aircraft Systems are applied to set the scope of aircraft performance and drive metrics computation. Four candidate Well Clear definitions, two primary and two secondary, varying from 1500 to 2500 ft in their horizontal miss distance and from 0 to 25 sec in modified tau, are selected for future analyses.
This paper investigates effects of limited surveillance volume on the alerting performance of a Detect and Avoid (DAA) system for unmanned aircraft systems (UAS). The surveillance volume accounts for an airborne sensor capable of detecting non-cooperative aircraft. Independent variables include four candidate DAA Well Clear (DWC) definitions and five surveillance volumes. Open-loop alerting performance metrics are computed from the results of running a reference DAA algorithm on a large number of synthesized encounters. The speed range for the UAS traffic considered is between 40 and 100 kts. Results show that, with a 2.5 nmi sensor range, all four candidate DWCs allow at least an average of 25 seconds warning alert times before a loss of DWC. Cumulative distributions of the intruder's bearing and elevation at the first warning alert suggest that ±10 • and ±140 • , respectively, are sufficient for alerting > 95% of the encounters that lead to losses of DWC.
Detect-and-Avoid (DAA) systems are essential to the safe operations of Unmanned Aircraft Systems, and have the objectives of mitigating collisions with and remaining Well Clear of manned aircraft. This paper analyzes four candidate DAA Well Clear definitions for noncooperative aircraft using mitigated performance metrics of DAA systems. These DAA Well Clear definitions were proposed in previous work based on their unmitigated collision risk and maneuver initiation range. In this work they are evaluated using safety and operational suitability metrics computed from a large number of representative encounters. Results suggest that although the four candidate DAA Well Clear definitions provide comparable safety, the alerting characteristics give preference for the DAA Well Clear definition without a temporal parameter.
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