NTSB Factual Report

On April 8, 2018, about 1711 eastern daylight time, an MD Helicopter 600N, N602BP, operated by High Line Helicopters, LLC, was destroyed when it collided with a wooden power line support structure and terrain in Smethport, Pennsylvania. The commercial pilot was seriously injured and two linemen were fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed for the power line construction flight, which was conducted under the provisions of Title 14 Code of Federal Regulations Part 133. The flight departed an unimproved landing zone adjacent to the accident site.

The power lines (3) were newly constructed in mountainous terrain and were oriented approximately east/west. They were supported by a series of structures of either wood (dual pole, H-frame) or steel (single pole) construction. A static line was affixed to the top of the structures above the power lines. The purpose of the flight was to remove the static line from the wheeled, pulley device (dolly) that temporarily secured the static line and permanently secure the static line to the structure. One lineman completed the task from the skid of the hovering helicopter, while a second lineman passed tools and equipment back and forth from inside the helicopter.

The steps taken to complete the task included wrapping the line with a spiraled wire coating (armor rod), attaching a safety strap (safety), a ratcheting chain lifting device (hoist) each attached to the top of the structure pole, and then placing the static line attachment device (shoe) to the line. The line was then hoisted into position and bolted to the structure. The safety, hoist, and dolly were then removed from the structure and static line, and the helicopter repositioned to the next structure to repeat the task.

In an interview, the pilot reported that the entire crew met earlier in the day, and flew to a structure to assess the work and tools required to complete the assigned task. They landed, refueled, and departed on the accident flight. The crew completed one structure, and the pilot hovered the helicopter into position to complete the work on the next structure. The lineman attached the first half of the armor rod ahead of the dolly, and manipulated the line and the dolly to complete the wrap. According to the pilot, the lineman opened the spring-loaded locking gate on the dolly above the static line to wrap the second half of the armor rod, which was "normal," and prior to the attachment of the safety . About that time, the pilot felt the helicopter was "pulled" toward the structure. He made cyclic and pedal inputs to avoid the structure, but "all I remember is rolling over the structure." When asked, the pilot said he neither felt nor heard anything unusual prior to the helicopter being pulled to the structure.

The helicopter descended vertically between and adjacent to the two-pole structure. The tailboom and all six rotor blades separated from the helicopter during the descent.

According to Federal Aviation Administration (FAA) records, the pilot held a commercial pilot certificate with ratings for rotorcraft-helicopter and instrument helicopter. The pilot's most recent FAA second-class medical certificate was issued April 5, 2017. According to the operator, he had accrued approximately 6,200 total hours of flight experience, of which 250 were in the MD 600N. The operator estimated that that pilot had accrued 3,000 hours performing power line operations.

The helicopter was manufactured in 1998 and was equipped with a Rolls-Royce/Allison 250-C47 series, 600-hourspower turboshaft engine.

Maintenance-record excerpts revealed the helicopter's most recent 100-hour inspection was completed February 4, 2018 at 5,120.8 total aircraft hours.

At 1653, the weather reported at Bradford Regional Airport (BFD), 10 miles west of the accident site, included an overcast layer at 4,100 ft, 10 statute miles visibility, and wind from 290° at 10 knots. The temperature was -3°C, the dew point was -12°C, and the altimeter setting was 29.95 inches of mercury.

The helicopter was examined at the accident site about 1,600 ft elevation, and all major components were accounted for at the scene. The wreckage was contained largely at the bottom of the wooden H-structure that was struck, with the six rotor blades separated at the hub and scattered at various distances on the south side of the power lines. One rotor blade travelled approximately 300 ft down the hill (west) of the structure. The tailboom separated and was about 70 ft west of the structure. Striating marks consistent with wire contact were visible on top of the left skid forward of the front crosstube.

The wreckage was recovered from the accident site to a secure facility for further examination at a later date.

The safety strap was suspended from a cross-brace of the H-structure, and the hoist was found next to the fuselage. Each appeared undamaged. Examination of the structure poles and the static line revealed signatures consistent with blade strikes. The dolly was in its swiveling mount and facing 180° from its operational position. Damage signatures to the pole above its mounting matched the dimensions of the dolly. The dolly was recovered from the top of the structure, and examination revealed it was intact except for the locking gate, which was fractured. The fracture surfaces displayed features consistent with overstress. The dolly was retained for further examination at the NTSB Materials laboratory.