Propeller at high incidence

Abstract

Existing small-incidence theory is generalized by use of a propeller solidity based on an average blade chord. With this solidity, simple expressions are developed for sixteen possible derivatives such as propeller normal (or side) force. In addition, an expression is derived which indicates that the ratio of normal force at high incidence to normal force slope at zero inflow equals the tangent of the angle of incidence, provided that both quantities have equal advance ratios as determined from the velocity normal to the propeller disk. Thrust, torque, and power at high incidence are likewise derived as ratios to the zero incidence value. Except for a small dependence on solidity, these ratios are independent of propeller geometry. Good correlation is shown with experimental thrust and power ratios to an incidence of 85°.