Impact of Propeller Design and Placement on Propeller-Driven Rotor Hover Performance and Scaling

After systematic testing of scaled propeller-driven rotor models in hover, and successful correlation of the test data with prediction methodology, a scaling study was conducted for a range of aircraft gross weights from 100 lbs to 20,000 lbs. From previous studies it became evident that propeller sizing and spanwise location on the main rotor blade were key for overall good main rotor performance. The impact of propeller design and placement on propeller-driven rotor hover power was estimated from the isolated propeller performance and propeller-driven rotor configuration. Propeller-driven rotor hover power was compared to a conventional shaft-driven isolated main rotor and a shaft-driven single-main rotor helicopter. The scaling study showed that, for a well designed propeller-driven rotor, the hover power was comparable between the propeller-driven and shaft-driven isolated rotor/single main rotor designs. Finally, a disk loading sensitivity analysis was performed which found that the propeller-driven rotor should have a low disk loading to prevent excessive rotor and propeller tipspeeds.