An Analysis of Airborne Collision Risk During UAV Approach Phase

As the number of unmanned aerial vehicles (UAVs) takeoff and landing operations continues to grow, determining a minimum safe separation during the approach phase is critical for enhancing airspace capacity and operational efficiency. To improve the efficiency of unmanned aerial traffic management, ensure flight safety, and facilitate the safe application of UAVs in complex airspace environments, this study focuses on modeling airborne collision risks during the approach phase of multirotor logistics drones. Current research has three main limitations:First, most studies focus on open-category UAVs, with insufficient attention to the operational risks of specific-category logistics drones. Second, the existing literature emphasizes the cruise phase and lacks targeted analysis of theapproach phase. Third, many assessment models are adapted from manned aviation without adequately accountingfor the unique maneuverability and control characteristics of UAVs. Based on two typical entry methods of mainstream logistics unmanned aerial vehicles: horizontal entry with vertical descent and diagonal approach, this studyimproves the traditional probability model of position error and introduces a dynamic closed-loop control feedbackmechanism. The real-time characteristics of positioning sampling interval and speed adjustment are incorporated into the risk calculation. According to the characteristics of logistics unmanned aerial vehicles, the positioning errorand speed error parameters are adjusted, and a collision risk assessment framework applicable to the entry stage isestablished. Based on the safety target level, the minimum safe interval is calculated. The calculation results showthat as the initial interval between the two unmanned aerial vehicles increases, the collision risk shows a decreasingtrend. By setting the safety target level to 1 × 10^-7 accidents per flight hour and requiring that the initial intervalthroughout the entry stage meets the target level, the minimum safe interval is 21 m for the horizontal entry with vertical descent method and 26 m for the diagonal approach. This establishes a quantifiable safety evaluation framework for the air collision risk during the entry stage of unmanned aerial vehicles.