On September 18, 2015, about 0815 Pacific daylight time, a Schweizer 269C helicopter, N290R, sustained substantial damage during an off field landing, near Forest Grove, Oregon. The helicopter was registered to and operated by Oregon Roses Inc., under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot, sole occupant of the helicopter, sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for the positioning flight. The local flight originated from a private helipad about 0814. The pilot reported that during low altitude cruise to a nearby landing site, where it was planned to take on chemical spray, the engine lost power and the helicopter began to lose altitude. At the time, the pilot was flying about 40 knots and approximately 55 feet above ground level. During the auto-rotation, the helicopter struck some wires near the ground, which resulted in a dynamic rollover, and the helicopter came to rest on its left side, nearly inverted. Postaccident examination of the helicopter by a Federal Aviation Administration (FAA) inspector revealed that the main rotor blades and tail boom were substantially damaged. The helicopter was recovered to a secure local storage facility for further examination. Further examination of the helicopter by the National Transportation Safety Board investigator-in-charge, an FAA inspector, a Sikorsky Investigator, and a certified Airframe and Powerplant (A&P) mechanic revealed no evidence of any internal damage to the engine or its accessories. The oil dipstick reading indicated a quantity of 6 quarts. The exhaust remained attached and was intact. Continuity of all the engine controls was established. The lower spark plugs were removed and examined and all sparkplug electrodes exhibited normal wear signatures when compared to the Champion Check-A-Plug comparison chart. The crankshaft was rotated by hand and compression was obtained on all the cylinders. It was determined that an engine run could be safety accomplished. The engine was subsequently test run and functioned normally at a low power setting. The magnetos were switched from left to right and the corresponding RPM drop was observed during the run. The Sikorsky investigator and the certified A&P mechanic stated that the engine ran smoothly and that they observed no engine anomalies. The engine run was accomplished at a low power setting only, due to concerns over the damage sustained to the mast support structure and the helicopter's overall stability, after the removal of the main rotor blades and tail boom. The helicopter's main transmission, gear boxes, drive shafts, and rotor heads were examined and no anomalies were noted with the exception of the tail rotor drive shaft that was separated by a main rotor blade strike, just aft of the vertical stabilizer mounting point. Tail rotor drive continuity was established to the point where the tail boom was separated, and from the separation point to the tail rotor gearbox. Flight control continuity was established with the cyclic and collective. The electric cyclic trim system was operated during the exam with no anomalies noted. Examination of the fuel system revealed that the helicopter was equipped with a 49 gallon fuel tank. The tank sustained damage to the aft, outboard portion but remained intact, with no loss of fuel. The fuel screen was removed, and there was fuel in the screen housing. The screen was observed to be clean of debris. Fuel samples from the storage tank and helicopter were taken and later tested by the FAA using a water detection paste, with negative results. A review of the helicopter's maintenance records revealed that the engine and airframe underwent their most recent annual inspection on September 08, 2015, at an airframe total time of 2,050.9 hours. The time since the overhaul of the engine was 494.2 hours.