What happened
The pilot was operating the aircraft at an altitude of approximately 800 feet when the flight occurred roughly one mile offshore. During this phase of flight, the pilot reported a significant decrease in engine performance, specifically noting that the manifold pressure dropped from 29 inches of mercury to 20 inches of mercury. This loss of power was immediately reflected in the instrument readings, as the main rotor and engine revolutions per minute needles split, indicating a discrepancy between the two systems.
In an attempt to restore normal operation, the pilot activated the boost pump; however, this action produced no positive results. With the engine unable to sustain flight, the pilot initiated an autorotative descent. The aircraft ultimately impacted the water approximately one mile offshore in an area where the depth was only four feet. The impact resulted in substantial damage to the airframe.
Findings
The primary factor leading to the incident was the sudden loss of engine power indicated by the manifold pressure drop. Despite the pilot's attempt to utilize the boost pump, the mechanical failure persisted, necessitating an emergency water landing.