Compact vibration isolation systems for aircraft

A rotorcraft comprising:

• a fuselage;
• a fuselage airframe supporting the fuselage;
• a pylon assembly subject to vibration;
• and
• a plurality of liquid inertia vibration eliminator units interposed between the fuselage airframe and the pylon assembly, each liquid inertia vibration eliminator unit comprising:
• an outer housing coupled to the fuselage airframe, the outer housing forming an outer housing cavity;
• a spherical bearing disposed in the outer housing cavity and forming a spherical bearing cavity;
• a fluid chamber housing disposed in the spherical bearing cavity such that the spherical bearing is interposed between the fluid chamber housing and the outer housing;
• a piston disposed in the spherical bearing cavity and coupled to the pylon assembly;
• top and bottom fluid chambers disposed in the spherical bearing cavity on opposite sides of the piston and at least partially defined by the fluid chamber housing;
• a tuning passage providing fluid communication between the top and bottom fluid chambers;
• and
• a tuning fluid movable between the top and bottom fluid chambers via the tuning passage to at least partially isolate vibration between the pylon assembly and the fuselage airframe.