Accident Overview
On April 20, 2019, at 1930 central daylight time, a Robinson Helicopter Company R66, registration N766WC, impacted an unmarked powerline and terrain during an aerial application flight near St Jacob, Illinois. The helicopter was operated by Skyline Helicopters LLC under 14 Code of Federal Regulations Part 137. The flight was conducted under day visual meteorological conditions without a flight plan. The local flight had originated from St Jacob at 1915. The airline transport pilot sustained serious injuries, and the helicopter received substantial damage.
Sequence of Events
The pilot reported that the wheat fields to be treated were not conjoined and were oriented north/south. He approached from the south to apply pesticide. During an initial reconnaissance at about 100-150 feet above ground level, he compared the fields' features to customer-provided maps. He noted powerlines and poles traversing east/west across the northern field, with a branch extending toward the northwest.
For the north field, he set an east/west A-B line and sprayed in a back-and-forth pattern progressing northward. After reaching the northern edge, he set a north/south A-B line for the southern section of the north field and the entire south field, spraying both simultaneously. He acknowledged that the north/south line was less ideal for spraying but offered better visibility of powerlines by avoiding direct flight into the sun. He completed those passes without incident.
He then lined up for an eastbound trim pass along the southern edge of the north field, which had a tree line. With the sun behind him, he retracted his helmet visor. During the trim pass, he noticed a powerline ahead but was too close to avoid it. He felt the powerline contact the helicopter mast, and shortly thereafter, the helicopter began to shake violently before impacting the ground.
The pilot stated he had not previously identified the struck powerline, even during the north/south spray passes. He described the powerline as oriented north/south, spanning an abnormally long distance from a pole at the southern field edge to a northern pole that was part of the east/west powerline structure. He also reported no mechanical malfunction or failure of the helicopter.
Post-Accident Examination
Examination of the accident site revealed that the struck powerline was a copper wire approximately 1/4-inch in diameter and green in color. The powerline pole at the southern edge of the north field was located within the tree line, and the field vegetation was green.