20050103000409A

(-23) On January 3, 2005, at approximately 1345 local, N135NW, an EC-135 helicopter operated by omniflight helicopters was destroyed during a forced landing near the Casa Grande airport. The aircraft departed from williams gateway airport to conduct a part 135 flight evaluation and was conducting closed traffic pattern work at Casa Grande airport. After approximately 40 minutes of closed pattern work, while on right downwind for runway 5, the crew felt that the aircraft had flown through some turbulence. After turning base, as a descent was initiated, the aircraft began an uncommanded 60-90 degree bank to the right, followed by another 60-90 degree bank to the left. The PIC assumed the controls and initiated a powered descent while attempting to maintain a level attitude. At approximately 40-60 feet, with both crewmembers on the controls, aft cyclic was entered to flare the aircraft. The aircraft was witnesses to level momentarily, and then descend vertically to the ground. The crew does not recall if collective was applied to cushion the landing. The aircraft impacted the ground in a tail low attitude causing the tailboom to separate. The aircraft then contacted the ground on bothskids with significant force. Both skids spread, the right skid separated and flew up into the main rotor and was flung to the left side of the aircraft approximately 50 feet away. The aircraft then rolled to the left causing main rotor blade contact with the ground. All four blades were destroyed. The aircraft came to rest upright with the tailboom partially separated and displaced at a 45 degree angle to the right. The crew performed an emergency shutdown of the engines with the engine control switches (both engines were still operating). The crew was able to egress the aircraft unassisted and received only minor injuries.