History of Flight
On August 23, 2022, about 1447 central standard time, a Bell 206B helicopter, registration N770HP, was substantially damaged when it struck a marked, 1-inch diameter, energized 161K volt aluminum high-tension powerline cable near Whiteside, Tennessee. The pilot and the passenger/observer were fatally injured. The flight was conducted as a Title 14 Code of Federal Regulations Part 91 public aircraft operation, operated by the Tennessee Department of Safety.
The helicopter was participating in a joint-agency marijuana eradication mission that day. Earlier, the pilot and passenger stopped for lunch and fuel at Marion County Airport (APT) in Jasper, Tennessee, at 1248. After lunch, they departed at 1401 to assist with a missing person case unrelated to the eradication mission. They flew to a hotel where the missing person was believed to be, but did not locate them. On the return flight to rejoin the eradication mission, the helicopter struck the powerlines.
A witness driving eastbound on Highway 24 observed a dark-colored helicopter flying westbound just north of the interstate. The witness noted the helicopter was flying low and close to a set of powerlines, hovering, and not in distress. He then saw the helicopter strike the powerlines, observed an arc, and saw the helicopter spin several times before descending out of view. A broken section of powerline cable fell onto the interstate in front of his vehicle.
The pilot was not in communication with air traffic control and did not make distress calls. The helicopter was not equipped with video recording devices and operated outside radar or ADS-B coverage. A handheld Garmin 496 GPS recovered from the wreckage showed the helicopter was in a descending right-hand turn at the time of impact. The last recorded GPS position at 1447:16 indicated an altitude of 1,130 ft msl.
Aircraft Information
The Bell 206B is a two-bladed, 5-seat helicopter powered by a single Rolls Royce 250-C20J turbine engine. The Tennessee Department of Safety owned and operated the aircraft as a public use helicopter. Maintenance was conducted under a continuous inspection program. The last engine maintenance entry was on August 15, 2022, when a 150/300 engine inspection was completed per the Rolls Royce Maintenance Manual. At that time, aircraft total time (ACTT) was 5,668.0 hours, and engine total time was also 5,668.0 hours. The last entry in the electronic maintenance database on the day of the accident recorded an ACTT of 5,674.0 hours.
Wreckage Examination
The helicopter came to rest in heavily wooded, steep mountainous terrain on the west side of the powerlines. The nose was embedded in a ravine wall with the tail section pointing upward. There was no post-impact fire. The tail boom, minus the tail rotor, separated just aft of the horizontal stabilizer and was located downhill. The tail rotor (minus one blade) was found about 100 ft east of the main wreckage under the powerlines. The top portion of the vertical stabilizer separated and was found adjacent to train tracks north of the wreckage, exhibiting striated gouging marks consistent with powerline contact.
The cockpit and forward fuselage sustained extensive impact damage. The right-side pilot seat was equipped with cyclic and collective controls; both sets of anti-torque pedals were installed but separated from control tubes due to impact. Control system examination revealed numerous impact fractures consistent with overload from terrain impact. No preimpact mechanical malfunctions or failures were found that would have precluded normal operation.
The two main rotor blades were marked with red or white dots. The white blade had striated impact marks on its bottom surface about two-thirds outboard, consistent with powerline contact. The red blade exhibited arcing at the trailing edge tip. The engine remained secured and showed no evidence of preimpact mechanical malfunctions or failures.