Abstract: A helicopter rotor having flexible blades mounted to a drive shaft by means of hub arms, wherein opposing blade members are interconnected by a common spar passing across the rotor axis. The spar members are supported from the hub arms by spherical bearing members. The universal freedom of these bearing members provides torsional freedom for blade pitching motions without restricting blade flapping or in-plane bending.

Abstract: A cylinder-and-piston type hydraulic damper has spaced dual seals on its piston rods to provide annular cavities between seals. A fluid leakage line connects said cavities to the closed reservoir of a fluid leakage indicator which consists of a cylinder closed by a spring biased diaphragm which carries the indicating member of the indicator. The damper chambers on opposite sides of the piston are alternately supplied with fluid from the reservoir during operation of the damper by means of a shuttle valve, thus providing a closed and sealed fluid system including redundant seals with means for indicating that the damper needs servicing upon a predetermined loss of fluid from the reservoir.

Abstract: A helicopter main rotor which can be supported in two positions of elevation above the fuselage, and apparatus and method for moving the helicopter rotor with blades attached from a first elevated position above the fuselage wherein the rotor is supported from an extension shaft projecting from a first shaft to a second elevated position above the fuselage wherein the rotor is supported from the first shaft.