GB485299A - Improvements in and relating to sustaining rotors for aircraft - Google Patents

Abstract

485,299. Aircraft with rotary-wing systems. CIERVA AUTOGIRO CO., Ltd. Dec. 18, 1936, No. 34899. Convention date, Dec. 19, 1935. [Class 4] A blade for an aircraft sustaining rotor consists of two or more portions, the overall thickness of each of said portions being substantially uniform and smaller than the thickness of the adjacent portion inboard thereof, adjacent portions being joined by a relatively short tapered portion or portions. As shown, a rotor blade comprises sections 11a, 11b, lie. The blade spar is constructed with a variable thickness and is connected to the hub by flapping and drag pivots 8, 10 respectively. The sections are of substantially uniform chord and include ribs 18a, 18b, 18c made, e.g. of wood. The ribs are secured to fittings 19 riveted and welded to the spar. Nose strips 23 and trailing edge stringers 24 are provided. Weights 28 are bolted to the spar, sleeves 30 surrounding the bolts being stiffened by brackets 31. The ribs are covered with fabric. The weights are disposed at the ends of the various sections and a tip piece 16 is provided. The sections may have a gradual and progressive washout. As shown, the blade incidence (measured from the no-lift line) varies from 4¢ to 3¥‹ at 85 per cent span-and to 2¥‹ at the blade tip. The wing section has a substantially stable centre of pressure disposed at about 25 per cent of the chord from the leading edge throughout at least a major part of the normal range of attack and adapted to move rearwardly at angles of attack below 2‹. The centre of gravity of the blade sections is substantially coincident with or slightly ahead of the centre of pressure.