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A rotor hub system for a helicopter in which the rotor hub and pitch housing are fabricated predominately of composite material, the flap hinge, pitch hinge and lead-lag hinge contain elastomeric bearings and one step blade folding in either the forward or aft direction using the same drive system.

A rotor hub system for a helicopter in which the rotor hub and pitch housing are fabricated predominately of composite material, the flap hinge, pitch hinge and lead-lag hinge contain elastomeric bearings and one step blade folding in either the forward or aft direction using the same drive system. The rotor hub includes closed loop straps which define generally opposed lugs of the flap hinge, and the pitch housing includes a pair of closed loop straps which define the lugs of the lead-lag hinge and a lug of the flap hinge. The use of composite materials as the predominant material of the rotor hub and the pitch housing results in a highly load redundant structure permitting a reduction in size and number of parts, a reduction in drag, and an increase in reliability and safety.

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1. A rotor system for a helicopter, comprising: a rotor hub including a plurality of lug pairs partly defined by a plurality of composite closed loop straps, each lug pair partly defining a flap hinge; a plurality of rotor blades, equal in number to the pairs of lugs; and a plurality of rotor b

1. A rotor system for a helicopter, comprising: a rotor hub including a plurality of lug pairs partly defined by a plurality of composite closed loop straps, each lug pair partly defining a flap hinge; a plurality of rotor blades, equal in number to the pairs of lugs; and a plurality of rotor blade attachment means, one for each rotor blade, for attaching a respective rotor blade to the rotor hub at a respective pair of lugs, each rotor blade attachment means further defining with an associated lug pair the flap hinge partly defined by said lug pair. 2. The rotor system as defined in claim 1, wherein the rotor hub further includes a plurality of composite core structures on which a respective one of the plurality of straps is attached said cores also partly defining said lug pairs. 3. The rotor system as defined in claim 1, wherein the rotor hub further includes means for attaching the rotor hub to a rotor shaft of the helicopter. 4. The rotor system as defined in claim 3, wherein the means for attaching the rotor hub to a rotor shaft of the helicopter comprises a plurality of bolt groups. 5. The rotor system as defined in claim 3, wherein the means for attaching the rotor hub to a rotor shaft of the helicopter comprises at least one laminated block of alternating metal and composite plates defining a splined inner diameter. 6. The rotor system as defined in claim 5, wherein said straps include a plurality of layers, and wherein said at least one laminated block and said straps form a plurality of interwoven intersections. 7. The rotor system as defined in claim 1, wherein the plurality of blade attachment means comprises a plurality of pitch housing assemblies. 8. The rotor system as defined in claim 7, wherein each pitch housing assembly includes a composite pitch housing and a pitch shaft mounted at each end to an elastomeric bearing supported by the housing and capable of reacting both axial and radial loads. 9. The rotor system as defined in claim 8, wherein the pitch shaft comprises a composite pitch shaft. 10. The rotor system as defined in claim 8, wherein the pitch housing assembly further includes flap motion stop means mounted to the pitch shaft and supported by the housing. 11. The rotor system as defined in claim 10, wherein the flap motion stop means comprises a metal flap motion stop means. 12. The rotor system as defined in claim 8, wherein the pitch housing includes two composite closed loop straps, one of which forms a lug for attachment to a pair of lugs of said rotor hub, and both of which form a pair of lugs to which a rotor blade is attached. 13. The rotor system as defined in claim 12, wherein the pitch housing further includes a support section about which adjacent loops of one of the closed loop straps of said pitch housing extend. 14. The rotor system as defined in claim 13, wherein the support section comprises a composite support section, said support section supporting one end of the pitch shaft and defining a bearing surface for engagement with one of the elastomeric bearings. 15. The rotor system as defined in claim 14, wherein the pitch housing further includes stiffener means situated between adjacent extensions of one of the closed loop straps of said pitch housing. 16. The rotor system as defined in claim 15, wherein said stiffener means comprises composite stiffener means. 17. The rotor system as defined in claim 7, further comprising: a lag damper and blade folding means associated with each rotor blade and its corresponding pitch housing assembly, for providing lead-lag damping and folding for the associated rotor blade. 18. The rotor system as defined in claim 17, wherein the lag damper and blade folding means includes drive means which serves to actuate blade folding in both the forward and aft directions. 19. A rotor system for a helicopter, comprising: a rotor hub including a plurality of composite core structures assembled together and an equal plurality of composite closed loop straps, each attached to a respective core structure, said plurality of composite core structures and their associated composite closed loop straps defining a plurality of lug pairs each lug part partly defining a flap hinge; a plurality of rotor blades, equal in number to the pairs of lugs; and a plurality of pitch housing assemblies, one for each rotor blade, each pitch housing assembly defining part of a lead-lag hinge to which a rotor blade is attached, and part of the flap hinge of an associated lug pair for attachment to the rotor hub. 20. The rotor system as defined in claim 19, wherein the rotor hub further includes means for attaching the rotor hub to a rotor shaft of the helicopter. 21. The rotor system as defined in claim 20, wherein the means for attaching the rotor hub to a rotor shaft of the helicopter comprises a plurality of bolt groups. 22. The rotor system as defined in claim 20, wherein the means for attaching the rotor hub to a rotor shaft of the helicopter comprises at least one laminated block of alternating metal and composite plates defining a splined inner diameter. 23. The rotor system as defined in claim 22, wherein said straps include a plurality of layers, and wherein said at least one laminated block and said straps form a plurality of interwoven intersections. 24. The rotor system as defined in claim 19, wherein each pitch housing assembly includes a composite pitch housing and a pitch shaft mounted at each end to an elastomeric bearing supported by the housing and capable of reacting both axial and radial loads. 25. The rotor system as defined in claim 24, wherein the pitch shaft comprises a composite pitch shaft. 26. The rotor system as defined in claim 24, wherein the pitch housing assembly further includes flap motion stop means mounted to the pitch shaft and supported by the housing. 27. The rotor system as defined in claim 26, wherein the flap motion stop means comprises a composite flap motion stop means. 28. The rotor system as defined in claim 24, wherein the pitch housing includes two composite closed loop straps, one of which forms a lug for attachment to a pair of lugs of said rotor hub, and both of which form a pair of lugs to which a rotor blade is attached. 29. The rotor system as defined in claim 28, wherein the pitch housing further includes a support section about which adjacent loops of one of the closed loop straps of said pitch housing extend. 30. The rotor system as defined in claim 29, wherein the support section comprises a composite support section, said support section supporting one end of the pitch shaft and defining a bearing surface for engagement with one of the elastomeric bearings. 31. The rotor system as defined in claim 30, wherein the pitch housing further includes stiffener means situated between adjacent extensions of one of the closed loop straps of said pitch housing. 32. The rotor system as defined in claim 31, wherein said stiffener means comprises composite stiffener means. 33. The rotor system as defined in claim 19, further comprising: a lag damper and blade folding means associated with each rotor blade and its corresponding pitch housing assembly, for providing lead-lag damping and folding for the associated rotor blade. 34. The rotor system as defined in claim 33, wherein the lag damper and blade folding means includes drive means which serves to actuate blade folding in both the forward and aft directions. 35. A rotor hub for the rotor system of a helicopter, comprising: a plurality of composite core structures assembled together; and an equal plurality of composite closed loop straps, each attached to a respective one of the composite core structures, the composite core structures and associated composite closed loop straps forming pairs of spaced apart lugs, with each pair of spaced apart lugs partly defining a flap hinge. 36. The rotor hub as defined in claim 35, further comprising: means for attaching the rotor hub to a rotor shaft of the helicopter. 37. The rotor hub as defined in claim 36, wherein the means for attaching the rotor hub to a rotor shaft of the helicopter comprises a plurality of bolt groups. 38. The rotor hub as defined in claim 36, wherein the means for attaching the rotor hub to a rotor shaft of the helicopter comprises at least one laminated block of alternating metal and composite plates defining a splined inner diameter. 39. The rotor hub as defined in claim 38, wherein said straps include a plurality of layers, and wherein said at least one laminated block and said straps form a pluarlity of interwoven intersections.