Pylon mounting system for reducing helicopter vibration

In a helicopter with a fuselage and a pylon including a rotor, a mount for coupling the fuselage to the pylon while attenuating rotor excitation forces which comprises:

• a pair of fore/aft beams rigidly secured at the centers thereof to opposite sides of a portion of said pylon;
• a vertical pin rigidly secured to the end of each of said beams;
• a hollow vertical receptacle rigidly secured to the fuselage coaxial with each of said pins, each receptacle having an upper bore and a lower relatively larger reentrant bore;
• an annular elastomeric body connected between each pin and the upper bore of the corresponding receptacle, said elastomeric bodies having a predetermined composite spring rate of low stiffness relative to the pylon mass in order to resiliently support said fuselage from said pylon during level flight in an operational region immediately below the point where said pylon and fuselage would resonate so as to attenuate oscillatory forces from the rotor and thereby reduce vibration in said fuselage;
• and
• an enlarged foot rigidly secured to each pin and positioned within the reentrant bore of the corresponding receptacle, said feet and receptacles cooperating to rigidly limit vertical deflection between said pylon and fuselage;
• said elastomeric bodies being preloaded downward such that said pylon and fuselage are rigidly coupled by said feet and receptacles up to a predetermined rotor thrust below that required to achieve flight.

An attenuator mount for interconnecting the fuselage and pylon of a helicopter while attenuating rotor excitation forces, comprising:

• said pylon including at least one engine drivingly and rigidly connected to a transmission which drives a mass supporting a main rotor;
• at least three generally horizontal arms rigidly secured to the transmission of said pylon;
• spring means connected between the end of each arm and said fuselage for resiliently supporting said fuselage from said pylon during level flight;
• said spring means having a predetermined composite spring rate of low stiffness relative to the pylon mass selected to operate in a region immediately below the point where said pylon and fuselage would resonate in order to attenuate oscillatory forces from the rotor and thereby reduce vibration in said fuselage;
• and
• a vertical restraint assembly connected between said pylon and fuselage for rigidly limiting vertical deflection therebetween;
• said spring means being preloaded downward such that said pylon and fuselage are rigidly connected by said vertical restraint assembly up to a predetermined rotor thrust below that required to maintain flight.