A Three Dimensional Theory For The Ducted Propeller At Angle Of Attack

An inviscid theory is developed for the steady aerodynamic loading on a ducted propeller in forward flight at angle of attack. As a first approximation, the problem is regarded as the superposition of the given ducted propeller at zero incidence and a cylindrical duct of the same aspect ratio but of zero thickness and camber at the given incidence. This approximation is then improved to include the cyclic variation of the blade loading. Not only are the normal force and pitching moment changed but also a finite side force and yawing moment, unknown heretofore, are found. Explicit formulas are given to carry out numerical calculations and a limited comparison with experimental results show good agreement.