Application of an Inverse Airfoil design for Improved Proprotor Performance

Significant progress has been made to improve the aeroacoustic characteristics of an existing UAV/ drone (RQ-7B). A four-bladed pusher propeller that replaces the existing two-bladed propeller was designed using public domain analysis. A four-bladed rotor, operating at a reduced RPM and with an acoustic footprint substantially lower than the baseline two-bladed rotor, was chosen for its comparable propulsive efficiency. Further improvements in rotor performance have been achieved by using advanced low drag airfoils specifically designed for this rotor, with lower drag coefficients over a broad range of lift coefficients.