Purpose and Preflight Preparation
The pilot stated that the purpose of the flight was for the two passengers, both biologists, to conduct a low-level river and land survey. Before departure, the pilot discussed the planned route with the passengers, and all reviewed maps and sectional charts, emphasizing potential hazards such as wire crossings.
Flight Maneuvers and Initial Hazards
After takeoff, the pilot maneuvered the helicopter in a crab angle to facilitate the biologists' view out the windows, tracking along the riverbank with the nose pointed left. The helicopter maintained an altitude just above treetop level. About one hour into the flight, the pilot observed the first high-power line crossing. Approximately 20 minutes later, one of the passengers drew attention to another line crossing marked with marker balls.
Final Maneuvers and Wire Contact
As the flight continued, the river divided into numerous channels. A passenger advised the pilot on which channel to follow. After surveying one channel, the pilot made a 90-degree turn to circle back; it was then decided not to return to the channel's origin. The pilot then initiated a left turn to rejoin the river and immediately observed blue sparks and a wire contact on the upper windscreen bubble.
Damage and Post-Impact Conditions
The helicopter was substantially damaged after descending and coming to rest in 4.5 feet of water, approximately 50 feet from the power line. The pilot reported no preimpact mechanical malfunctions or failures that would have precluded normal operation.