GB1361174A - Helicopter rotor blade and method of fabricating same - Google Patents

Abstract

1361174 Helicopter rotor blade UNITED AIRCRAFT CORP 1 Feb 1973 [14 Feb 1972 19 July 1972] 5081/73 Heading B7W A helicopter rotor blade has a spanwise tubular spar 10, an outer skin 12 and rigid fluidimpervious filler material 14 between the spar and the skin, and an indicator (16), Fig. 2 (not shown), for indicating a change in pressure in the spar, and there are sparwise extending channels 17 located in the filler material and in communication with the outer surface of the spar. These channels communicate with a cap (18) at the blade tip which is vented to atmosphere through a spring valve (19), so that if a crack develops in the spar, gas therein may leak to atmosphere so that a pressure drop is registered. The channels 17 are formed by placing a resilient tube (20), Fig. 3 (not shown), against the spar before filling the skin with the filler and withdrawing it when the material has hardened; alternatively channels may be formed by strips of sheet material (22), Fig. 4 (not shown), bonded to the spar. In a further embodiment, spar 110, Fig. 6, is covered by a plurality of blankets 118 each consisting of a sheet (122), Fig. 8 (not shown), either having ribs (124) attached, leaving channels (135), Fig. 7A (not shown) between, or in which channels (135) are cut. The sheets (122) of adjacent blankets overlap, but the ribs do not abut, so that oblique transverse ducts 125 are formed, connecting the spanwise channels (135) with a spanwise duct (120), Fig. 7 (not shown), at the trailing edge of the spar 110. The aft part of the blade is filled with honeycomb material 114 which is perforated so that adjacent cells communicate with one another and with the duct (120) so as to form a sump for gas leaking from the spar so that a pressure drop may be indicated by indicator 116 in the event of a crack in the spar.