May 6, 1947. W. E. HUNT 2,420,174 ROTARY WING STRUCTURE Filed Oct. 3, 1942

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Patented May 6, 1947 2,420,174 UNITED STATES PATENT office ROTARY WING STRUCTURE William E. Hunt, Milford, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application October 31, 1942, Serial No. 464,069 5 Claims. (C. 244-23) - 2 This invention relates to a wing structure for 24 (Figs. 5, 6). The opposed sections 20 are aircraft, particularly to a wing or blade for a placed with the offsets in engagement to define, helicopter. as shown in Fig. 4, passages i 28 extending ver In helicopters, the rotating wing or blade pref tically through the rib. The leading ends of erably has a certain amount of flexibility in the flanges 26 of each rib are extended to form plane of the blade. An object of this invention is tongues 30 which enter recesses 32 in the upper to provide a wing structure capable of flexing and lower surfaces of the spar. These tongues Wtihout injury to the wing or the wing surface. are secured to the spar, and the plywood cover A feature of the invention is a longitudinal ing sheet 4 assists in holding them in position. Spar for a Wing Which may be made up of thin The trailing edges of sheet 4 are preferably plies of wood bonded together. Another fea faired down in line with the edge of the longitu ture is a rib made up of duplicate sections which dinal Spar. are held in Spaced relation to provide passages The trailing ends of the ribs may be connected through which attaching means for the wing to cable f6 by metal clips 34 bent around the covering may extend. 15 cable and secured to the spar to prevent any Another feature is a longitudinal spar to which relative movement between cable and spar. several rearwardly extending ribs are attached In attaching fabric covering 8, the passages With the trailing edges of the ribs held in spaced 28 in the ribs permit secure attachment of the relation by a cable. In this way as the wing is fabric covering by means of connecting threads flexed, the cable will permit the trailing ends 20 36 (Fig. 2) extending between upper and lower of the ribs to move toward each other. surfaces of the wing and engaging the covering. Other objects and advantages will be apparent It is to be understood that the invention is not from the specification and claims, and from the limited to the specific embodiment herein illus accompanying dra Wings which illustrate what is trated and described, but may be used in other now considered to be a preferred embodiment of 25 ways without departure from its spirit as defined the invention. by the following claims. Fig. 1 is a plan view of the helicopter Wing. I claim: Fig. 2 is a perspective view with parts broken 1. A rib for aircraft comprising, in combina away showing the wing structure. tion; a pair of contralateral members, each hav Fig. 3 is a sectional view through the wing. 30 ing upper and lower flanges, webs connecting Fig. 4 is a fragmentary plan view of the wing said flanges, offset surfaces on said webs for se ???cture With the cover removed to show the curing one member to the other; and means bond 10. ing said offset surfaces together; the offset Sur Fig. 5 is a Sectional view along the line 5-5 faces providing aligned upper and lower slots be of Fig. 4. tween said edges of said flanges, and elongated The Wing has a longitudinal spar to extending 35 vertical passages between the webs and the slots. the length of the wing and ribs 2 extending 2. A rib for aircraft comprising, in combina from the Spar to the trailing edge of the Wing. tion; a pair of contralateral members, each hav The Spair may be shaped to form the leading ing upper and lower flanges, webs connecting said edge of the wing, as shown, and may be covered 40 flanges, offset surfaces on said webs for Securing by a thin sheet of plywood 4. The spar may one member to the other; means bonding Said be made up of several thin strips of wood bonded surfaces of said webs together; the offset por together. tions providing elongated open passages between The trailing ends of the ribs are interconnected said webs and increasing the ratio of effective by a cable 6 fastened at its opposite ends to 45 solid area, to weight of said rib; and flange exten the ends of the longitudinal spar as shown in sions for mounting the rib. Fig. 1. Spar and ribs are covered by fabric 8. 3. A rib for aircraft comprising, in combina Each rib is preferably made up of opposed tion; a pair of contralateral members, each hav Sections 29, each formed from several thin sheets ing upper and lower flanges, webs connecting said of Wood bonded together by a plastic which may 50 flanges, flat surfaced offset portions of said webs be one of the familiar resins commonly used in for securing the inside edge of said flanges away the bonding of wood plies. from a plane containing the surface of the por Each Section 20 is channel-shaped and com tions; means bonding the surface of said portions prises a Web 22 With fianges 26 at top and bot together; the offset portions providing aligned tom. Each web has a series of integral offsets 55 upper and lower slots between said edges of said 2,420,174 3 4 flanges, and elongated passages between the webs intermediately to said clips for forming the trail and the slots; and a clip secured to all of Said ing edge of said blade, a blade COvering over flanges. lying all of said parts, and stitching for said 4. A rotor blade comprising, in combination, a cover extending through said slots and openings laminated spar shaping the leading edge of the 5 to opposite Surfaces of Said cover. blade and having recesses at its rear edges, ply VAMI E. EÜN. wood ribs, each rib having a pair of contralateral webs with offset portions and flanges spaced by 3 REFERENCES CITED Said portions to form a pair of open upper and The following references are of record in the lower slots between the flanges and elongated ver O file of this patent: tical passages between the webs, said flanges shaping the trailing portion of said blade, off UNITED STATES PATENTS set forward tips upon said flanges for fitting into Number Name Date Said recesses to mount the ribs upon said Spar, 1891,681 Messier ------Dec. 20, 1932 a leading edge cover overlying said spar and se 15 1949,785 Cierva ------Mar. 6, 1934 cured to the tips of Said flanges substantially 2,123,429 Klemmi ------July 12, 1938 flush with the trailing portion of said flanges, a 2,164,678 Bennett ------July 4, 1939 cable connected at its ends to inboard and out 2,303,707 Pullin ------Dec. 1, 1942 board portions of said spar and intermediately 998,978 Norris ------July 25, 1911 to the tips of Said ribs for forming the trailing 20, 1,344,640 LeinWeber ------June 29, 1920 edge of said blade, a blade covering. Overlying all 1789,240 Leitner ––------Jan. 13, 1931 of said parts, and stitching for said cover ex 2,329,366 Weill et al.------Sept. 14, 1943 tending through said slots to opposite surfaces FOREIGN PATENTS of Said cover. V 5. A rotor blade comprising, in combination, a 25 Number Country Date spar forming the leading edge of the blade and 737,063 French ------Sept. 27, 1932 having recesses at its rear edges, plywood ribs, 387,904 British ------Feb. 16, 1933 each rib having webs turned outwardly to form contralateral flanges Spaced to form a pair of open OTHER REFERENCES upper and lower slots in registry with elongated 30 Civil Aeronautics Bulletin No. 27-Sept. 1940 vertical Openings, said flanges forming the trail page 66. ing portion of said blade, the forward tips of Airplane Mechanics Rigging Handbook-Hartz said flanges fitting into said recesses, a leading & Hall, published by Ronald Press Co., New York, edge cover overlying said spar and secured to the 1930, page 50. - tips of said flanges substantially flush with the 35 Civil Aeronautics Bulletin 27-Sept. 1940, en trailing portion of Said flanges, clips at the tips titled “Pilot’s Airplane Manual,” by N. O. Ander of Said ribs, a cable Connected at its ends to the son, pages 60 to 65 (page 66 cited previously). inboard and outboard portions of said spar and