GB452366A - Improvements in and relating to aircraft with autorotative wings - Google Patents

Abstract

452,366. Aircraft with rotary-wing systems. LA CIERVA, J. DE, Bush House, Aldwych, London. Jan. 16, 1935, No. 1548. [Class 4] In aircraft of the gyroplane type having a rotor-starting transmission from power plant to rotor including clutch means and having means for varying the mean pitch angle of the rotor blades, the sustaining rotor blades have a, non-uniform cross-sectional profile such that a relatively small part of the blade has a stable pitching moment characteristic and the remainder of the blade has an unstable pitching moment characteristic, the parts having relatively stable and unstable pitching moment characteristics being so relatively positioned and proportioned and having pitching characteristics so related that the overall pitching characteristic of the blade is substantially neutral. The tip portion of the blade may have an aerofoil section of greater aerodynamic efficiency than the rest of the blade. Fig. 1 shows a blade b of uniform chord having a uniform aerofoil section of the "unstable" type, such as shown in Fig. 2, which has an unstable pitching moment characteristic whilst the portion of the blade between section lines 3-3 and the tip is of the "stable" type shown in Fig. 3. The two sections may be blended into one another or there may be an abrupt transition giving the blade a stepped appearance. In a modification Fig. 5, a blade b<1> of uniform chord and profile is provided at the tip with a flap or tab f which is tilted slightly upwards so as to give this portion of the blade a stable characteristic. Specifications 264,965, [Class 4], 452,364, and 452,36.5, are referred to. The invention is stated to be particularly applicable to gyroplanes adapted to take-off in the manner described in Specification 420,322.