Abstract: A helicopter load vibration damper having an outer cylinder with closed upper and lower ends. A piston is slidably mounted within the cylinder to define a chamber between the piston and the cylinder's lower end. The chamber is pressurized with an inert gas such as nitrogen, with the gas pressure being adjustable to suit the load which is to be transported. A rod is fixed to one side of the piston, extends through the chamber and protrudes through the lower end of the cylinder for attachment to the load. A hydraulic shock absorber is connected between the opposite side of the piston and the upper end of the cylinder. An anti-rotation mechanism prevents the shock absorber from rotating relative to the rod, around the vibration damper's longitudinal axis. The anti-rotation mechanism incorporates a tube which encircles the shock absorber, within the outer cylinder. A pin used to couple the shock absorber to the piston is also coupled to the tube.