The pilot stated that as he was flying low over the apple orchard and rolled out of a turn, the engine began to lose power, which was accompanied by the engine out horn and light. He decreased his airspeed towards zero, and performed a hovering autorotation into the orchard. During the landing the rotor blades impacted the trees and the tail boom separated from the main fuselage. An examination of the engine revealed that Pc air tube that connects the Pc air filter to to the Power Turbine Governor (PTG) was disconnected. The b-nut that connects the tube to the Pc air filter was present on the tube but not threaded onto the Pc air filter boss. Review of the maintenance records showed that about 6 hours prior to the accident the turbine assembly and bleed valve had been replaced. The threads on both the Pc air filter and b-nut did not exhibit any damage or abnormalities. The removal and reinstallation of the Pc air tube was conducted as part of the documented maintenance. According to the engine manufacturer's technical representative, the disconnection of the Pc air tube during engine operation would result in a loss of engine power.