Improvements in or relating to aeronautical propeller blades and methods of locating the pitch axis of variable-pitch propeller blades

摘要

518,626. Screw propellers. TENNANT, W. J. (Aviation Patents, Inc.). Aug. 29, 1938, No. 25325. Drawings to Specification. [Class 114] Screw propeller blades intended to be mounted for pitch adjustment are arranged so that the blade axis lies within the confines of the blade throughout the major length and the centre of gravity of the blade is located toward the leading edge of the blade from the blade axis whilst the centre of pressure of each blade section is closer to the leading edge than the centre of gravity, whereby there is 'substantial balance between the centrifugal and aerodynamic moments about the blade axis. The centre of pressure is selected so that the net blade torque at the extreme limits of the normal range of operation will be in opposite directions, and also the aerodynamic movement exceeds the centrifugal moment under take off conditions, whilst the reverse occurs at maximum flight conditions. At the time when the centrifugal moment equals the aerodynamic moment for a selected flight condition, the centrifugal, moment predominates in an inner radial zone of the blade whilst aerodynamic moment predominates in an outer zone and the two moments are locally equal at the junction of the two zones.