Incident Details
The pilot of the helicopter reported that the aircraft had been 'topped off' with fuel prior to departure. Approximately 1 hour and 10 minutes after takeoff, a loud 'bang' was heard, followed by sputtering from the engine and a subsequent decay in engine RPM. The pilot initiated an autorotation in response to the power loss.
Landing and Damage
The autorotation was conducted into a small clearing situated in a wooded, swampy area. During the landing sequence, the main rotor blades struck and severed the tail boom of the helicopter. The aircraft came to rest in the clearing.
Engine Examination
Following the incident, an examination of the engine was performed. No discrepancies were found that would have resulted in a loss of engine power. The precise cause of the power loss remains undetermined.