Incident Description
The pilot was performing aerial burning operations over a wooded area when he heard a loud bang emanating from the engine area of the helicopter. At the time, the helicopter was approximately 20 feet above the tallest tree in the vicinity, with the aerial torch still burning. The pilot reported that the RPM audio warning immediately activated and the helicopter began to descend.
Pilot Actions
In response, the pilot keyed the microphone and called out "Engine failure, engine failure" twice. He then directed the helicopter toward the clearest area available for a forced landing. After impacting the trees, the pilot managed to crawl out of the wreckage. The helicopter was subsequently destroyed by the impact and ensuing fire.
Investigation Findings
An investigation revealed that the main drive shaft, part number 206-040-110-3, had failed. This failure disconnected the engine from the main rotor, leading to a loss of rotor drive and resulting in the accident.