Robinson Helicopter Company R44 II accident near Audubon, Iowa, March 31, 2020

The NTSB's narrative final · quoted from the NTSB record

The pilot and passenger were conducting a low-altitude raptor survey flight. Witnesses reported seeing the helicopter flying just prior to its impact with powerlines about 85 ft above the ground. The witnesses described the helicopter in a gentle turn toward the sun prior to impact. One witness noted that he did not hear any unusual noises from the helicopter prior to impact. Automatic dependent surveillance-broadcast data from the helicopter provided information indicating the pilot flew six flights in the 24 hours prior to the accident. The accident flight was the fifth that day and occurred approximately 10 hours after the pilot had begun flying that morning. Intervals between flights that day were 17, 24, 35, and 29 minutes. These working conditions were conducive to fatigue. Research on pilot fatigue in a noisy, vibrating helicopter simulator found considerable increases in subjective fatigue after 6 hours of short repetitive flights. At the end of this period, some helicopter pilots who participated in the study said they were so fatigued that they did not feel safe to fly a real helicopter. As subjective fatigue increased, study pilots demonstrated increasingly frequent “lapses” in performance. While missions the day of the accident were longer than those in the study, flights were conducted at low altitude and involved repetitive observation tasks that required a high state of awareness to avoid terrain and obstacles. This heightened state of awareness would produce a mental workload similar to the shorter repetitive IFR flights in the study; therefore, it is likely that similar effects would be expected, including lapses in performance as fatigue increased. These lapses in performance were described in the study as outliers caused by moments of inattention. The accident pilot’s ability to avoid the same wire nine times earlier that day, but not avoid it during the accident flight is consistent with an attentional “lapse.” This potential lapse combined with over 10 hours since awakening, and 8 hours flight time already accumulated the day of the accident suggests that the pilot was likely fatigued during the accident flight and that fatigue likely challenged the pilot’s ability to see and avoid the power line.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.

Other NTSB records under N107EH the same tail number, which may have belonged to a different aircraft at the time