GB644478A - Improvements in rotor blade airfoils - Google Patents

Abstract

644,478. Helicopter rotor blades. PREWITT, R. H. Feb. 24, 1948, No. 5468. Convention date, Jan. 28, 1947. [Class 4] A rotor blade for a helicopter comprises a main structural member shaped to conform to the leading edge of the aerofoil, chord members extending toward the trailing edge of the aerofoil and a cover enclosing and attached to the main and chord members. The main member is hollow, the wall thickness increasing from the tip toward the root 2 where the section becomes annular and is reinforced by a collar 6 welded to it. Chord members 21-24, 44 are attached to and extend between the rear wall 31 of the main member and a trailing edge member 25. A thin sheet 4 of stainless steel or like metal surrounds, and is adhesively attached to, the leading edge and rib members. Hot gases for de-icing purposes enter the blade via a flexible tube 55 (Fig. 2, not shown), and a manifold 15, Fig. 1. At a predetermined temperature of the blade or of the gases a thermostat 29 operates a member 30 and allows hot gases, previously confined to a chamber 19 at the root, to flow through holes 18, unimpeded by plates 36, into the structural member 3 where they are forced by centrifugal action to the blade tip and exhausted through a vent 20 normally closed but constructed to open when the internal pressure rises. A weight 8 is pivoted at 9 to the blade tip and may be adjusted by a screw 10 to move the blade centre of gravity in a chordwise direction whilst manufacturing errors in the longitudinal balance may be compensated by changing this weight. Fig. 2 (not shown) illustrates a helicopter having one rigid and one flapping blade.