N333ST

The flight instructor said the student was practicing a stable hover at 2 to 3 feet altitude, when they experienced an uncommanded loss of altitude with a slight drift to the right. The student said he made a correction and thought the helicopter might touch the ground and lift up again. When the right skid contacted the taxiway, the right rear skid shoe stuck in the asphalt surface and the aircraft rolled right, pivoting on the right skid. The flight instructor immediately bottomed the collective and pushed the cyclic left; however, the aircraft continued to roll onto its right side. Subsequently, the tail boom was bent up and partially separated, the windscreen structure was broken, the main rotor blades were damaged, and the fuselage was wrinkled.

The flight instructor said the helicopter belonged to the company and had been equipped with “flat” prototype skid shoes approximately 10 inches in length. When the aircraft touched the ground with lateral movement, the edge of the aft right skid shoe dug into the asphalt causing the aircraft to roll right. The flight instructor said that after this accident, the company modified their skid shoe design by rounding the shoes to conform to the landing skids.