Accident Narrative
The pilot of the helicopter reported that an abnormal vibration developed while en route to a local practice area. Concerned about the unusual vibration, he decided to land as soon as possible to investigate its source. He executed a power-on approach to a terraced paved area located to the right of his intended course. While on approach with a northerly heading, as the pilot was flaring for landing, control was lost after the main rotor blades contacted the terraced terrain to his right-front. The pilot stated that the engine was performing normally and that he did not experience a loss of engine power. Winds at the accident site were from the south at an estimated 10 to 13 knots.
Pilot Actions
The pilot recalled receiving a Safety Alert Letter from the Robinson Helicopter Company three days prior to the accident. The letter, issued on June 25, 2002, addressed unusual vibrations and the possibility of a main rotor blade crack, stating: "IF MAIN ROTOR VIBRATION INCREASES RAPIDLY OR BECOMES SEVERE DURING FLIGHT, LAND IMMEDIATELY." The pilot indicated this as the reason for his landing attempt.
Post-Accident Examination
Both tail rotor blades were broken off about 3½ inches from their outboard mount points, with severe leading edge damage. One main rotor blade was bent aft and up from its normal position, leaving the trailing edge buckled. The other main rotor blade was bent aft and down, also leaving the trailing edge buckled. Small cracks were observed on both main rotor blades near the root fitting and spar cover area. Due to these cracks, the sealant was removed from both blades and they were subjected to a dye penetrate inspection per Robinson Helicopter Company Service Letter 21A. No indications of cracks in the root fitting material of either blade were found.