Incident Overview
A helicopter pilot reported experiencing a low-frequency vibration shortly after departing from a heliport. The pilot decided to return to the heliport to investigate the source of the vibration.
Landing and Gyration
After landing, the pilot positioned the collective to its full down position. At that point, the helicopter began a violent forward and aft gyration, which resulted in the main rotor blades striking the ground.
Post-Incident Examination
Inspection of the landing skids revealed that the left shock strut assembly (designated as 4H) had separated from the landing skid. The separation was attributed to severe exfoliation corrosion at both attaching lugs. The other three strut assemblies remained attached to the skid.
Technical Details
No further information regarding the helicopter type, registration, operator, location, or personnel was provided in the source.