Stressing of Airscrew Blades

THE estimation of the stresses in airscrew blades presents difficult aerodynamic and structural problems, the solution of which often involves considerable labour even after simplifying assumptions have been made. The aerodynamic problems associated with airscrew design have received considerable attention and extensive wind tunnel tests have been made, but on the other hand, the literature on the elastic problems presented by the airscrew is nothing like as extensive, and is mainly concerned with the twisting of the blades and the frequencies of blade vibrations. There then appears to be some justification for taking the present opportunity to concentrate on the strength side of airscrew design, dcaliug especially with the blade bending stresses which arise. On this account methods of estimating the air loads on the blades will not be dealt with here, where it will be assumed that the distribution of the air loads on the blades is known.