ERA18FA122

The helicopter pilot's failure to maintain adequate clearance during power line construction work, which resulted in the helicopter's main rotor striking and becoming entangled with a wire and a subsequent dynamic rollover and collision with terrain. Contributing to the accident was the pilot's and linemen's decision to continue work without a secondary safety device installed, which was contrary to standard operating procedures.

The pilot of the helicopter was conducting a power line construction flight. The power lines were supported by a series of structures made of either wood (dual-pole, H-frame) or steel (single pole). 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 structures. One lineman completed the task from the skid of the hovering helicopter, and another lineman inside the helicopter passed tools and equipment back and forth to the lineman on the skid. The accident occurred when the crew (the pilot and the two linemen) were working on the second structure, which was constructed of wood. During work on that structure, the helicopter hovered facing westbound adjacent to the wooden structure with the pilot, both linemen, and the structure on the helicopter's left side. The static line sloped upward aft of the helicopter toward the uphill structure and downward and to the right toward the downhill structure. The initial steps taken for the task included wrapping the line with a spiraled wire coating (armor rod) and attaching a safety strap (safety). The lineman on the helicopter skid 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" before the attachment of the safety. About that time, the pilot felt the helicopter being "pulled" toward the structure. The pilot stated that he made cyclic and pedal inputs to avoid the structure but reported that "all I remember is rolling over the structure." The pilot stated that he neither felt nor heard anything unusual before the helicopter was pulled toward the structure. Visual examination of the static line, helicopter rotor blades, and visual and metallurgical examination of the dolly revealed that, as the lineman on the skid wrapped the armor rod, and before he attached the safety, the aft portion of the main rotor struck the static line, which broke the locking gate that secured the line inside the dolly. Once free of the dolly, the static line fell between the uphill and downhill structures and over the left front skid of the helicopter, which created the pivot point over which the helicopter rolled inverted. The pilot and the linemen began work without installing a safety. According to the operator's director of safety, the safety strap aboard the helicopter was "not long enough" to install it before work began. The holding company of the subsidiary that hired the operator as an independent contractor had a safety manual for linemen who performed work from helicopters. The manual indicated that "secondary securement systems shall be utilized" when clipping wire (permanently securing a static line to the structures).

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 about 6,200 hours of total flight experience, 250 hours of which were in the 600N helicopter. 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 600-horsepower turboshaft engine. At the time of the accident, the helicopter's Hobbs meter indicated a total of 5,203.6 hours. Maintenance record excerpts showed that the helicopter's most recent 100-hour inspection was completed on February 4, 2018. The helicopter had accumulated 5,120.8 hours at that time. An FAA airworthiness inspector reviewed the helicopter's maintenance records. The inspector found numerous record-keeping errors but overall compliance with hourly and calendar inspections as well as compliance with airworthiness directives. The helicopter was installed with aluminum diamond-plate flooring, which required the removal of the left-side cabin door, and a 6061-T6 aluminum pipe. A search of the FAA's aircraft registry records and the helicopter's maintenance logbooks found no information regarding these installations. Also, no records were found showing FAA approval for these modifications or company documentation of weight and balance computations that reflected the changes. According to section 2-1 of the MD 600N flight manual, operations with the left-side cabin door removed were authorized, but operations with the pilot (right) seat removed (resulting in a left-seat command configuration) were not. Neither of these modifications was reflected in the helicopter's weight and balance or aircraft records. Title 14 CFR 91.107(a)(3) required that all passengers be seated in an approved seat and properly secured with a seatbelt during aircraft movement. The helicopter's cabin had no passenger seats installed. Weight and balance computations based on pilot and lineman weights, cargo, and three different fuel states (full, one-half, and one-third tank) showed that the helicopter, as configured, was likely within weight, lateral, and longitudinal center-of-gravity limits for the accident flight. On April 8, 2018, about 1711 eastern daylight time, an MD Helicopters 600N helicopter, N602BP, 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. The helicopter was being operated by High Line Helicopters, Inc., as Title 14 Code of Federal Regulations (CFR) Part 133 external load flight. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed from an unimproved landing zone adjacent to the accident site. Three power lines, which were newly constructed in mountainous terrain and oriented approximately east/west, were supported by structures that were constructed of either wood (dual pole, H-frame) or steel (single pole). 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 structures ("clipping wire"). One lineman completed the task from the skid of the hovering helicopter, and another lineman inside the helicopter passed tools and equipment back and forth to the lineman on the skid. The steps to complete the task on each support structure included wrapping the line with a spiraled wire coating (armor rod), attaching a safety strap (safety), ratcheting a chain lifting device (hoist) to the top of the structure pole, and placing the static line attachment device (shoe) to the line. Afterward, the line was hoisted into position and bolted to the structure, and the safety, hoist, and dolly were then removed from the structure and static line. The pilot then repositioned the helicopter so that the linemen could repeat the steps on the next structure. During a postaccident interview, the pilot reported that he and the linemen (the crew) met earlier in the day and flew to one of the structures to assess the work and tools required to complete the task. The helicopter then returned to the landing zone and was refueled before departing on the accident flight. The crew completed one structure, and the pilot hovered the helicopter into position so that work could begin on the next structure. In a written statement, the pilot stated that the pole where the accident occurred was at "a slight inside angle" but was considered to be a "safe" area in which to work. According to the pilot and the operator, the helicopter was hovering "inside the bite," which was the triangular area comprising the wire from the uphill pole, the turn at the accident pole, and the wire to the downhill pole. The "base" of the triangle was the horizontal line from the uphill pole to the downhill pole. The operator indicated that the "bite" had a vertical dimension as well. Once the helicopter was in position, the lineman on the helicopter skid 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" before the attachment of the safety. About that time, the pilot felt the helicopter being "pulled" toward the structure. The pilot stated that he made full right cyclic and full left pedal inputs to avoid colliding with the structure but that "all I remember is rolling over the structure." The pilot said that he neither felt nor heard anything unusual before the helicopter was "pulled" toward the structure. A witness to the accident stated that, while the helicopter was hovering, its nose turned away from the pole, and the helicopter "was violently forced back to the pole." The witness also stated that the tail section struck the pole and that the helicopter "broke in two," after which the helicopter appeared "to fall straight down." The witness did not see the helicopter's impact but stated that the engine "continued to surge." The helicopter descended vertically between and adjacent to the dual-pole structure. The tailboom and the six rotor blades from the main rotor separated from the helicopter during the descent. The accident site was at an elevation of about 1,600 ft. All major components were accounted for at the scene. The wreckage was contained largely at the bottom of the wooden H-frame 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 traveled about 300 ft down the hill (west) of the structure. The tailboom separated and was found 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 cross-tube. The six main rotor blades remained inside their respective pitch housings, and the laminated steel strap sets ("strap packs") were fractured at the hub. The blades showed varying degrees of chordwise and spanwise twisting and bending. One of the rotor blades displayed a concave dent 2.25 inches from the tip. The dent was about 1 inch wide and 0.75 inch deep. The overall dimensions of the dent and the dimensions of the individual striating marks inside it were consistent with the total dimensions of the static line and its individual strands. The safety strap was suspended from a cross-brace of the H-frame structure, and the hoist was found next to the fuselage. Both app