Incident Overview
A helicopter was en route from Morgan City, Louisiana, to South Marsh 243C, an offshore location in the Gulf of Mexico. Approximately five minutes after departure, while flying at an altitude of 500 feet above ground level (AGL), the aircraft experienced a sudden loud, continuous chattering sound accompanied by violent vibrations. The onset was described as without warning.
Emergency Landing
As the pilot initiated an emergency landing toward a canal, the vibration ceased entirely when the helicopter descended to about 50 feet above the trees. However, the helicopter then began an uncommanded right turn. The pilot responded by performing an autorotation and deploying the floatation system. The helicopter touched down on the water in a level attitude at a forward speed of 20 to 25 miles per hour. The aircraft subsequently came to rest on its side.
Post-Accident Examination
Inspection after the landing identified damage to the tail rotor. One tail rotor blade had been sheared from the leading edge to the trailing edge at its outboard end. Energy dispersive x-ray analysis (EDXA) of the sheared area detected two distinct compositional zones: one containing lead and chromium, and another containing titanium, iron, nickel, and chromium. Optical microscopy at 60x magnification of the lead-chromium area revealed the presence of red paint particles embedded in the blade. The investigation was unable to determine the specific object that struck the tail rotor blade.