N107EH

HISTORY OF FLIGHTOn March 31, 2020, about 1626 central daylight time, a Robinson R44 helicopter, N107EH, was destroyed when it was involved in an accident near Audubon, Iowa. The pilot and passenger were fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 aerial observation flight.

According to the operator, the purpose of the flight was to conduct a raptor survey of a 442 square-mile area in western Iowa under contract with another company whose biologist was the passenger on the helicopter at the time of the accident. The helicopter was flying a north-south grid pattern when two witnesses observed the helicopter flying in a southerly direction at low altitude. One witness observed the helicopter strike the bottom two wires of a power line before it impacted terrain and burst into flames. The second witness lost sight of the helicopter just before it impacted the wires but heard the impact and observed the helicopter descend with wires intertwined in the main rotor. Both witnesses thought the helicopter was in a turn to the southwest, toward the sun, prior to the hitting the wires. One witness described the helicopter in a gentle turn, not in a way that looked like the pilot was aware of the high lines.

Automatic dependent surveillance- broadcast (ADS-B) data showed that during the final moments of the accident flight, the helicopter was travelling 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 kts. The final recorded data point was about 160 ft north of the wires that were struck. There were no deviations in heading or altitude before the end of the data. The ground elevation at the accident site was about 1,460 ft. The flights within the survey area were conducted at altitudes about 100 ft above the ground. Examination of the flight track data for the previous flight showed that the helicopter had crossed the power lines on at least two occasions during the previous flight. (See Figure 1.)

Based on ADS-B flight data and the pilot’s flight records, he had flown a flight the night prior to the accident that concluded in the Sioux Falls, South Dakota, area, lasted about 45 minutes, and was followed by about 9 hours of non-flight activity. It is not known what the pilot did during this time of non-flight activity. On the day of the accident the pilot flew five flights lasting 51 minutes, 18 minutes, 3 hours 29 minutes, 3 hours 11 minutes, and 22 minutes, respectively. The first flight of the day took off at 0629. Between these flights were periods of non-flight activity lasting 17 minutes, 24 minutes, 35 minutes and 29 minutes, respectively. It was reported that the biologist joined the flight after the helicopter arrived at Arthur N. Neu Airport (CIN), Carroll, Iowa, after the second flight of the day.

Figure 1: Plot of the survey area and the helicopter flight path on the day of the accident.

Figure 2: 3-dimensional view of the final portion of the accident flight path.

WRECKAGE AND IMPACT INFORMATIONThe helicopter came to rest in a field next to the west side of Robin Avenue and south of 240th Street. The wires that were struck ran along the north edge of 240th Street, strung between poles that were about 100 ft. tall. The estimated height of the wires struck was about 85 ft. above the ground.

Figure 3. Location of powerlines, helicopter flight path, and wreckage.

A post-impact fire consumed most of the cabin section of the helicopter. A postaccident examination of the helicopter after it was removed from the site revealed no preimpact anomalies. A large wire was found wrapped around the rotor mast just below the main rotors.

Figure 4: Powerline wires wrapped around main rotor mast.