CEN21FA330

The pilot was conducting an aerial application flight in the helicopter. Just before the accident, a witness saw the helicopter completing east and west spray passes over a cornfield. The helicopter flew two consecutive spray passes over power transmission lines that crossed the field, but, on the third spray pass, the helicopter flew underneath the powerlines while heading west. The witness then entered a nearby barn and, shortly thereafter, heard a loud “boom,” and the barn shook momentarily. The witness exited the barn and saw smoke rising from the cornfield. The witness and another person subsequently found the helicopter engulfed in flames. According to the wreckage debris path through the cornfield, the helicopter was flying to the east when a main rotor blade impacted a powerline that crossed over the field. The powerline at the point of damage was about 28 ft above the ground. The corn crop under the transmission lines was 8 to 10 ft tall. The operator stated that, during aerial application flights, the helicopter was typically flown 10 ft above the crop to ensure optimal spray disbursement. If the 10.75 ft tall helicopter flew 10 ft above the 8 ft high corn crop, then the main rotor system would be at the same elevation as the transmission line. The position of the sun relative to the helicopter at the time of the accident would likely not have impaired the pilot’s ability to see the powerlines as the helicopter flew to the east. Postaccident examination revealed no evidence of a pre-existing mechanical malfunction or failure that would have prevented normal operation of the helicopter. Thus, it is likely that the pilot decided to intentionally fly the helicopter under the powerlines.

According to the Robinson R44 II Pilot Operating Handbook, the helicopter’s height was 10.75 ft. The operator stated that, during aerial application flights, the helicopter was typically flown 10 ft above the crop to ensure optimal spray disbursement. Postaccident review of available maintenance documentation revealed no unresolved maintenance tasks or issues with the helicopter. On July 19, 2021, about 1600 central daylight time, a Robinson R44 II helicopter, N44BJ, was destroyed when it was involved in an accident near Elgin, Minnesota. The pilot was fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. A witness saw the helicopter completing east and west spray passes over a cornfield, with each additional spray pass progressively closer to the north end of the field. The witness saw the helicopter make two consecutive spray passes over powerlines that crossed the field, but, during the third spray pass, the helicopter flew underneath the powerlines while heading west. The witness then entered a nearby pole barn and, shortly thereafter, heard a loud “boom,” and the pole barn shook momentarily. He exited the pole barn and saw smoke rising from the cornfield. The witness and another person subsequently responded to the accident site where they found the helicopter engulfed in flames. The Mayo Clinic, Rochester, Minnesota, performed an autopsy of the pilot. His cause of death was blunt force and thermal injuries. Toxicology testing by the FAA Forensic Sciences Laboratory detected no carboxyhemoglobin, ethanol, or tested-for drugs. At the time of the accident, the sun’s position relative to the accident site was along a west-southwest heading (249° true) and was about 48.6° above the horizon. The Federal Aviation Administration (FAA) revoked the pilot’s second-class medical certificate in a letter dated February 22, 2021. The pilot had been seriously injured in a forced landing accident that occurred about 11 months before this accident. The FAA sent a letter to the pilot, dated August 10, 2020, requesting a medical examination to determine if he remained qualified to hold a second-class medical certificate, but the pilot did not undergo the requested evaluation. On May 17, 2021, the pilot completed an application for a new medical certificate. On his last medical certificate application, the pilot reported 4,000 hours of total flight experience, 1,100 hours of which were flown during the previous 6 months. In addition, the pilot answered “no” when asked if his medical certificate had ever been revoked. The aviation medical examiner requested that the pilot provide information about the previous helicopter accident, but the pilot had not provided the requested records before this accident occurred. The pilot’s logbook contained only a single logbook endorsement for the required training, which was required by Special Federal Aviation Regulation 73 to act as pilot in command of aRobinson R44 helicopter. The date of the endorsement was not provided. The initial impact location was a multiphase power transmission line, as shown in figure 1. The transmission line consisted of 24 aluminum-conducting strands over 7 steel strands, and three lines were present. The western line remained intact, the center line was frayed, and the eastern line was severed. The frayed transmission line at the point of damage was about 28 ft above the ground. The corn crop under the transmission lines was 8 to 10 ft tall. Portions of the swashplate yoke, a blade droop tusk, the pilot’s headset, and plexiglass fragments were located under and immediately east of the power transmission lines. Figure 1. Powerlines above the cornfield with a red rectangle identifying the center powerline (main photograph) and an inset showing the frayed center powerline. The wreckage debris path, as shown in figure 2, measured 292 ft between the power transmission lines and the main wreckage. The wreckage debris path through the cornfield was on a 090° heading. The helicopter impacted terrain in a 15° descent angle. Fractured portions of the spray booms, cabin door, and plexiglass were scattered along the wreckage debris path. Figure 2. Wreckage debris path with the red circle showing the location of the wire strike. The main wreckage, as shown in figure 3, included remnants of the cabin, landing skids, cockpit, engine, main rotor transmission, main rotor head, main rotor blades, aft fuselage, sheaves, tail rotor driveshaft, tailboom, tail rotor gear box, and tail rotor blades. The product tank was relatively intact, and its support frame was located about 15 ft north of the main wreckage. Most of the cabin and cockpit were destroyed by the postimpact fire. Flight control continuity could not be established due to the extensive damage sustained during the impact and postimpact fire. Figure 3. Main wreckage at the accident site. One of the two main rotor blades remained intact but folded in half during impact. The other main rotor blade fractured about 3 ft from the blade tip and exhibited damage consistent with impact with a power transmission line, as shown in figure 4. The outboard 3 ft of the main rotor blade, as shown in figure 5, was located about 465 ft south of where the helicopter impacted the power transmission line. Figure 4. Main rotor blade fracture with damaged power transmission line. Figure 5. Outboard 3 ft of main rotor blade (Source: Helicopter operator). Postaccident examination revealed no evidence of a pre-existing mechanical malfunction or failure that would have prevented normal operation of the helicopter.