Incident Overview
A helicopter sustained a hard landing and rolled over after the certified flight instructor (CFI) attempted to recover from a simulated autorotative descent. According to the CFI, as he tried to level off at an altitude between 75 and 100 feet above ground, the helicopter experienced a sharp left yaw accompanied by a loss of main rotor RPM. Despite corrective actions, the helicopter touched down with the left skid low, resulting in a rollover.
Post-Accident Examination
Following the accident, the engine was removed and placed in a test cell. When started, the engine operated at approximately 2,550 RPM instead of the expected 2,700 RPM. During a differential compression test, the No. 3 cylinder showed only 5 psi. Subsequent examination of that cylinder by its manufacturer revealed discolorations typical of high temperature operations, as well as wear on the exhaust valve seating face and exhaust valve guide.