A rotor aircraft has a fuselage with a rotor mounted above by a rotor shaft. An arm is pivotally engaged with a lower portion of the rotor shaft and pivotally engaged with the fuselage, enabling the rotor to move with little restriction vertically and horizontal in all directions relative to the fuselage as the rotor rotates in order to isolate rotor oscillations. An infinitely variable air spring is used to counter vertical and fore and aft loads. Damping in the form of elastomeric materials, piston seal friction, and fluid flow through an orifice may be added as required.