The effect of blade twist on the characteristics of the c.30 autogiro

Abstract

An analysis of the blade motion and force characteristics of the standard Cierva C.30 autogiro rotor is made, taking into account the torsional flexibility of the blades. The results are applied to the steady motion and pitching equilibrium of the whole machine. Using the physical constants of the blades, the analysis has been carried out for the cases of a mean profile drag coefficient over the blade elements equal to 0.014 and 0.012, and a speed range from zero to 130 m.p.h. The most important assumption of the present investigation is that the blades remain straight under all circumstances. The other approximations are not expected to have any great influence. The blades are found to twist to the extent of several degrees, in the sense that the mean pitch angle (at any radius) round the circle is decreased and that superimposed on this there is a periodic variation. Both effects increase with the forward speed until at the highest speed the outer portion of the advancing blade is twisted to below the no-lift angle of the section.