Accident Overview
A helicopter was observed flying northbound, parallel and just east of a north-south highway. Witnesses reported that the aircraft entered an autorotative landing approach, crossed over the highway, cleared power lines, and impacted in an open field on a westerly heading. The helicopter then burned. Witnesses noted the helicopter was descending at approximately 45 degrees when it went out of sight behind trees.
Investigation Findings
Examination of the accident site revealed that the helicopter impacted in a nose-high attitude while moving to the left. The wind at the time was from 340 degrees at 16 knots. After impact, the helicopter began to disintegrate, with wreckage scattered over a distance of 108 feet.
Engine Examination
A teardown of the engine revealed damage consistent with a lack of power and low RPM. No other evidence of pre-impact malfunction or failure was found during the teardown.
Pilot's Previous Observations
According to reports, the pilot had noted vibrations during left turns on a previous flight. Additionally, the pilot had to "beep up" the engine after lifting off to a hover, and then had to "beep down" after landing to prevent overspeeding.