Abstract: Methods and apparatus are provided for a tubular composite structure with particular application to the design and assembly of space vehicles. The apparatus, designated herein as an X-strut, comprises alternately crossing tow-placed layers of parallel strands of a composite material, to form top and bottom intersecting faces. Alternately crossing strand layers are built up from the bottom faces to form the side walls of the tubular composite structure. The top and bottom faces and the side walls are configured to form intersecting tubular members in an X-shape. The layers of strands run continuously through the intersecting tubular members to form an integral joint, without the need for adhesive bonding or mechanical fasteners.

Abstract: A universal joint for use in a pitch cone rotor system in a helicopter is comprised of crossed lift beams, one beam of which is coupled to the rotor hub and the other beam of which is coupled to the driven rotor shaft. The two crossed lift beams are coupled to each other through a cruciform case. The cruciform case in turn is coupled to each of the crossed lift beams by means of a plurality of flexures. The flexures and cruciform case are made of composite fiber materials and the flexures are soft enough to permit angular and translational deflections of the crossbeams with respect to each other thereby tending to smooth out and reduce sudden changes in rotor speed between the shaft and rotor system and thereby tending to make rotor speeds more uniform. The crossed lift beams are further coupled together at the center of their crossing by a flexible elastomeric tension link which conducts rotor loads between the two beams when the rotor develops negative lift loads on the ground and in flight.

Abstract: An improved flexure member in a helicopter rotary system is devised wherein the flexure member is made of wound monofilamentary resin impregnated material comprising a fiber matrix and is formed in a flat strap disposed through a rotary hub of the rotor system and integrally extends from the flat strap to form a transition member and then to a cruciform flexure member having an X-shaped cross section. The cruciform member then extends and attaches to an outboard fitting adapted for coupling to the root of a rotor blade. In one embodiment the fiber matrix is wound around cylindrical lugs which forms the outboard fitting in combination with the integral extension of the cruciform member. The cruciform member is particularly characterized by including a woven X-shaped reinforcing fabric disposed within the X-shaped member about which fabric the monofilamentary layers are formed thereby forming each leg of the X-shaped cruciform.

Abstract: A compact, rugged, streamline, stiff, pitch control system is devised in a helicopter by concentrically nesting a cyclic pitch control tube and collective pitch control tube within the drive shaft and stationary mast of a helicopter rotor system. The collective pitch control tube terminates in an upper inclined flange which engages a stationary swashplate by means of a bearing member disposed in an inclined bearing raceway in the stationary swashplate. The stationary swashplate in turn is rotatably coupled through a universal joint to the cyclic pitch control tube. Relative rotation of the cyclic pitch control tube with respect to the collective pitch control tube adjusts the stationary swashplate to a selected inclination with respect to the longitudinal axis of the control tubes and of the helicopter mast. A rotating swashplate is rotatably coupled to the stationary swashplate and transmits the angular orientation of the stationary swashplate to the pitch case of each rotor blade as appropriate.

Abstract: There is disclosed a method of manufacturing a filament wound blade including the steps of forming a spar by winding a plurality of resin impregnated filaments in side-by-side relationship between a pair of spaced apart spools. The spools are held in their spaced apart orientation to maintain the filaments in their unidirectional orientation and a flexible bondable bag fitted over the spar filaments and inflated to assume a generally cylindrical configuration. Resin impregnated shell filaments are wound in a helical pattern about such bag to form a shell and the bag then deflated and placed in a female mold defining the desired contour of such blade, and such bag then re-inflated to thereby cause the shell to assume such desired contour.