Incident Overview
A helicopter experienced a loss of lift shortly after takeoff and subsequently descended into a lake. The aircraft was operated at approximately 29 pounds below its maximum gross weight. The field elevation at the departure point was 4200 feet. Additionally, the calculated hover ceiling out of ground effect was noted as a relevant parameter.
Flight Sequence
The pilot had climbed to an altitude of 4300 feet and turned downwind in winds estimated at 10 to 15 knots. During this maneuver, the pilot reported a belief that he 'may have lost transitional lift,' a phenomenon that can affect rotorcraft performance when transitioning from out-of-ground-effect to in-ground-effect hover or vice versa.
Investigation Findings
A thorough investigation was conducted to determine the cause of the loss of lift. No evidence of any pre-impact failure of the aircraft or its engine was found. The investigation did not identify any mechanical or structural deficiencies that could have contributed to the accident.