Background
The helicopter was flying low over a river. The pilot and a policewoman serving as a traffic observer were on board. The pilot wanted to show the island to the observer.
Maneuver Details
The pilot flew a low pass to the south over the island at an altitude of approximately 30 feet AGL. He then initiated a climbing right turn at about 40 knots indicated airspeed to pass back over the island.
Aircraft Response
During the climbing turn, the helicopter experienced an excessive roll in the direction of the turn. The nose began to tuck down. The pilot reported that engine and main rotor RPM remained within the green range throughout the maneuver.
Pilot Input
To address the unusual attitude, the pilot applied only opposite cyclic. He did not increase engine power or add collective pitch. He was not sure if he used any left pedal to help reduce the turn rate.
Impact
The helicopter struck the water in a slight right bank attitude with the nose low.