Practical payload assessment of a prototype blade for agricultural unmanned rotorcraft

Unmanned rotorcraft represents a new paradigm in agricultural activities. Rotor-blade design to improve lift performance was necessitated because payload-mounted flights suffer from a lack of lift. A prototype of rotor blade, comprising the V2008B airfoil, was assessed on an agricultural rotorcraft. The lift corresponding to the collective pitch angle (CPA) and rotor speed was measured on field and compared with a base-line blade. Measurements demonstrated that the prototype blade could sustain a maximum payload of 589 N, resulting in a total lift of 1256 N. Thus, an increase of 10.5 % in total lift was accomplished, compared with a base-line of 1137 N. Simulation also indicated that total lift equals 1269 N at CPA = 10°, approximately 1.0 % greater than the experimental lift. However, a practical spray payload would be reduced due to the ground effect and uncertainty, existing during an anchored field experiment. The ground effect from the experimental operation close to the ground would reduce 10 % of the total lift, resulting in 1138 N for hovering. Furthermore, uncertainty existed in stick control inputs and local wind conditions, resulting in fluctuations of rotor speed and payload. The standard deviation of net lift was ±45.33 N; therefore, the minimum net lift of the low envelope assessed from the uncertainty analysis would be 426 N.