GB606784A - Improvements in or relating to rotary wings for aircraft - Google Patents

Abstract

606,784. Rotary wing aircraft. FAIREY AVIATION CO., Ltd., and HODSON, C. F. Jan. 18, 1946, No. 1839. [Class 4] A rotary wing system has each blade divided transversely into at least an inner, or hub, section and an outer, or tip, section, the inner section being arranged for the reduction of its resistance to the airflow which, during the retreating travel of the blade, produces a downward reaction or reversed flow. Fig. 2 shows a construction in which the inner section 15 of the blade is slidable along the main spar 13 and can be telescoped over the fixed outer section 12. The section 15 is moved outwardly by the pilot when vibration or flapping of the blade occurs. In the arrangement according to Fig. 4 the outer and inner blade sections 16, 18 are adapted for cyclical pitch variations in opposite senses. The outer end of the inner section may be secured to the inner end of the outer section, and the pitch variation applied at the centre of the inner section, the pitch angle of the latter being thereby graduated along its length. Fig. 5 shows a modification in which the outer and inner sections 22, 26, and intermediate sections 27, 28 are interconnected by flexible rods 29, 30 to effect a progressive change of pitch between the inner and outer sections. The differential pitch adjustments of the blade sections are effected by separate concentric swashplates. Fig. 7 shows a construction of blade in which the ratio between the effective lengths of the inner and outer sections 41, 39 may be varied by coupling an intermediate section 42 to either section by means of bolts 46, 47 operated by a longitudinal member 45. To avoid the necessity of cyclical pitch change, the inner blade portion may be of an aerofoil section suitable for travel in either direction, e.g. a semiellipse or segment of a circle, and preferably having appreciable lift at zero incidence.