Flight Attitudes and Spray Patterns of a Roll-Balanced Agricultural Unmanned Helicopter

Abstract

<abstract><title><italic>Abstract. </italic></title> Unmanned agricultural helicopters have certainly made precise and timely aerial spraying possible in Korean farming. A rotorcraft system depends on various dynamic factors for a roll-balanced maneuver. Even with the aid of an autopilot system, conventional agricultural helicopters cannot maintain a lateral balance due to issues with physical dynamics. Most agricultural helicopters exhibit biased downwash, resulting in an uneven spray pattern. To address this problem, a roll-balanced agricultural helicopter with an elevated-pylon tail rotor system was developed (Koo et al., 2010). In this study, we evaluated the effectiveness of a roll balanced helicopter during hovering and cruising spray maneuvers by analyzing flight attitudes and spray patterns. The hovering spray was performed at a height of 3.5 m, and the pattern was determined by a string deposition analysis system. The practical cruise spray maneuver was performed at a 50-m long cultivating field, and the pattern was acquired using water sensitive strips. Spray deposits from the left and right sides of the fuselage were compared and evaluated. For the hovering and cruise spray maneuvers, fluctuations in the roll and pitch angles were found for both the manual pilot and autopilot operations. However, the average values of roll angle were maintained at 0°, supporting the lateral balance. The spray patterns and roll attitudes under conditions of hovering and cruising were steadily balanced. The uniformity of the spray patterns with the roll-balanced helicopter was satisfactory in both manual pilot and autopilot operations. Consequently, the balancing behavior of the developed helicopter resulted in left-right balanced spray patterns with coverage rates of 20% to 25% during aerial applications.