Unmanned aircraft systems (UAS) will be required to equip with sense-and-avoid (SAA) systems in order to fulfill the regulatory requirement to remain "well clear" of other air traffic. This study investigates the effects that different well-clear metrics have on the rate of well-clear violations and evaluates the distribution of distances between aircraft at a wellclear violation in high-altitude enroute airspace. The first analysis determines the predicted rate at which violations of well clear would occur between UAS and manned aircraft operating under instrument flight rules, indicating the frequency with which a sense-andavoid system would create a nuisance alert. This analysis is done both with and without an algorithmic model of air traffic control (ATC) separation provision services. The second analysis determines the relationship between time-based well-clear metrics and the range at which the violation would occur, a relationship that may inform the required SAA surveillance range and the frequency with which violations would occur despite ATC separation standards still being maintained. The analyses are carried out using a fast-time simulation capability of the entire US air traffic system over a single day, including 3000 UAS and more than 50,000 manned aircraft. Results indicate that, without any separation provision, a UAS would encounter a manned aircraft with a range tau (defined as the ratio of the relative range to range rate) of 60 seconds only every six hours. Approximately 75% of such encounters would occur outside the ATC separation standard of 5 nmi.
This paper documents a study that drove the development of a mathematical expression in the detect-and-avoid (DAA) minimum operational performance standards (MOPS) for unmanned aircraft systems (UAS). This equation describes the conditions under which vertical maneuver guidance should be provided during recovery of DAA well clear separation with a non-cooperative VFR aircraft. Although the original hypothesis was that vertical maneuvers for DAA well clear recovery should only be offered when sensor vertical rate errors are small, this paper suggests that UAS climb and descent performance should be considered-in addition to sensor errors for vertical position and vertical rate-when determining whether to offer vertical guidance. A fast-time simulation study involving 108,000 encounters between a UAS and a non-cooperative visual-flight-rules aircraft was conducted. Results are presented showing that, when vertical maneuver guidance for DAA well clear recovery was suppressed, the minimum vertical separation increased by roughly 50 feet (or horizontal separation by 500 to 800 feet). However, the percentage of encounters that had a risk of collision when performing vertical well clear recovery maneuvers was reduced as UAS vertical rate performance increased and sensor vertical rate errors decreased. A class of encounter is identified for which vertical-rate error had a large effect on the efficacy of horizontal maneuvers due to the difficulty of making the correct left/right turn decision: crossing conflict with intruder changing altitude. Overall, these results support logic that would allow vertical maneuvers when UAS vertical performance is sufficient to avoid the intruder, based on the intruder's estimated vertical position and vertical rate, as well as the vertical rate error of the UAS' sensor. * mod = modified tau threshold I. Introduction AFE integration of unmanned aircraft systems (UAS) into the U.S. National Airspace System (NAS) requires that they interoperate with existing safety systems for manned aircraft. One requirement that is particularly difficult for UAS to satisfy is the requirement for aircraft to perform see-and-avoid to remain "well clear" of other aircraft. 1 This requirement is in the FAA's Federal Aviation Regulation §91.113(b), which dictates that, "When weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft. When a rule of this section gives another aircraft the right of way, the pilot shall give way to that aircraft and may not pass over, under, or ahead of it unless well clear." §91.113 also covers right-of-way rules for air vehicle operations. If two aircraft get too close and lose "well clear," they are expected to maneuver immediately and attempt to regain it. However, the exact definition of the term "well clear" is not given in the regulations, and is subject to interpretation by the pilot. This is diffi...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.