What happened
The flight departed from an island after the completion of a mosquito control inspection. While cruising at 200 feet above the water with a setting of 23 inches manifold pressure and 2800 rpm, the engine began missing and failed to produce sufficient power to maintain flight. The engine sputtered before regaining full power.
The pilot initiated an autorotation procedure with a forward airspeed of 50 knots. During this process, the pilot split the needles and set the engine rpm to 2,000. As the helicopter decelerated at 50 feet above the water, the engine returned to operational status. The pilot then joined the needles and established an attitude intended to continue flight; however, the landing skid contacted the water.
The investigation
Investigators performed a test run of the engine. Prior to the test, the magnetos and the ignition harness required repairs due to damage sustained during the event. Following these repairs, the engine test run was completed, and no discrepancies were identified at any power settings.