History of Flight
On March 31, 2020, at approximately 1626 central daylight time, a Robinson R44 helicopter, registration N107EH, was destroyed in an accident near Audubon, Iowa. The pilot and passenger sustained fatal injuries. The helicopter was operating under Title 14 Code of Federal Regulations Part 91 as an aerial observation flight.
According to the operator, the flight's purpose was to conduct a raptor survey over a 442-square-mile area in western Iowa under contract with another company, whose biologist was the passenger. The helicopter was flying a north-south grid pattern when two witnesses observed it flying south at low altitude. One witness saw the helicopter strike the bottom two wires of a power line before impacting terrain and bursting into flames. The second witness lost sight of the helicopter just before it hit the wires but heard the impact and observed the helicopter descend with wires entangled in the main rotor. Both witnesses believed the helicopter was turning southwest, toward the sun, prior to the wire strike. One witness described the turn as gentle, not indicating pilot awareness of the power lines.
Automatic Dependent Surveillance-Broadcast (ADS-B) data revealed that in the final moments, the helicopter was traveling south over Robin Avenue, approaching 240th Street, at an ADS-B-reported geometric altitude of 1,475 ft with a ground speed of about 85 knots. The last recorded data point was approximately 160 ft north of the wires that were struck. No deviations in heading or altitude were observed before the data ended. The ground elevation at the accident site was about 1,460 ft. Flights within the survey area were conducted at altitudes roughly 100 ft above ground. Flight track data from the previous survey flight showed the helicopter had crossed the same power lines on at least two occasions.
Based on ADS-B data and pilot flight records, he had flown a flight the night before the accident that lasted about 45 minutes and concluded in the Sioux Falls, South Dakota, area, followed by about 9 hours of non-flight activity. The pilot's activities during that time are unknown. On the accident day, the pilot flew five flights lasting 51, 18, 3 hours 29 minutes, 3 hours 11 minutes, and 22 minutes, respectively. The first flight of the day departed at 0629. Between flights, non-flight periods lasted 17, 24, 35, and 29 minutes. It was reported that the biologist joined the flight after the helicopter arrived at Arthur N. Neu Airport (CIN) in Carroll, Iowa, following the second flight of the day.
Wreckage and Impact Information
The helicopter came to rest in a field adjacent to the west side of Robin Avenue, south of 240th Street. The wires that were struck ran along the north edge of 240th Street, suspended between poles approximately 100 ft tall. The estimated height of the wires struck was about 85 ft above ground.
A post-impact fire consumed most of the cabin section. Examination of the helicopter after removal from the site revealed no pre-impact anomalies. A large wire was found wrapped around the rotor mast just below the main rotor blades.