Abstract: A vibration isolation system for a passenger carrying helicopter with which the crew seats in the cockpit area and the floor in the passenger area are decoupled from the airframe thereby isolating the seats and floor from the airframe vibrations. In addition, the fuel tanks of the helicopter are isolated from the airframe so that a force feedback from the fuel tank to the airframe resulting from the changing fuel quantity is effectively eliminated. The system employs nodal isolators which both isolate (decouple) and support the particular structural mass in question.

Abstract: A vibration isolation system wherein a vibrating mass such as a helicopter rotor-transmission assembly is spring coupled to a body to be isolated, such as the helicopter fuselage, at a plurality of points. Each coupling point includes, in addition to a coupling spring, a weighted lever arm pivotally connected to the vibrating mass and to the body, with the body-to-lever pivot connection lying between the center of gravity of the arm and the vibrating mass-to-lever pivot connection. The coupling spring is in the form of a torsion spring, e.g., torsion bar, coupled between the body and the lever arm at the pivot connection therebetween. Vibratory forces of a predetermined frequency transmitted from the vibrating mass to the body through the spring are substantially cancelled by inertial forces generated by the lever and applied to the body through the body-to-lever pivot connection, thus isolating the body from the vibrating mass at the predetermined frequency.