Accident Overview
The pilot reported that while flying at low altitude over an apple orchard and rolling out of a turn, the engine began to lose power. This was accompanied by the activation of the engine out horn and warning light. The pilot decreased airspeed toward zero and executed a hovering autorotation into the orchard. During the landing, the rotor blades struck trees, resulting in the separation of the tail boom from the main fuselage.
Investigation Findings
Post-accident examination of the engine revealed that the Pc air tube, which connects the Pc air filter to the Power Turbine Governor (PTG), was disconnected. The b-nut that attaches the tube to the Pc air filter was found on the tube but was not threaded onto the Pc air filter boss. Inspection of the threads on both the Pc air filter and the b-nut showed no damage or abnormalities.
Maintenance records indicated that the turbine assembly and bleed valve had been replaced approximately six flight hours before the accident. The removal and reinstallation of the Pc air tube were part of that documented maintenance procedure.
According to a technical representative from the engine manufacturer, the disconnection of the Pc air tube during engine operation would result in a loss of engine power.