Abstract
Rotary-wing unmanned aerial vehicles (UAVs) are increasingly used for low-altitude atmospheric monitoring, but rotor-induced flow can bias samples taken close to the airframe or near the ground. This paper presents the design and feasibility assessment of a lightweight UAV-mounted winch that lowers an air-sampling pod beneath a hovering aircraft, allowing the UAV to remain at a safe altitude while separating the sampling point from the immediate rotor-wash region. The prototype integrates a compact motorized spool, a 10 lb (4.5 kgf, 44.5 N) test Stren Original monofilament tether, a 3 V geared DC motor, a DRV8833 dual H-bridge driver and an HT12E/HT12D radio-frequency control link. Design targets include a pod mass below 200 g, deployment speeds of 0.02-0.15 m/s and initial operating depths of 10-20 m below the UAV. Bench verification confirmed bidirectional actuation, command latency below 100 ms and reliable retrieval of a simulated 200 g pod with a total auxiliary payload of approximately 280-310 g. The main remaining limitation is wind-induced pendulum motion; future work should therefore add quantitative swing measurement, damping and closed-loop depth control before field deployment.