A helicopter being used in construction of new power lines hit a wooden power line support structure when it crashed and killed two workers April 8 near Smethport, the National Transportation Safety Board reported.

The agency, which is investigating the crash with the Federal Aviation Administration, released a preliminary report this week.

The two men who died were Shane Filkins, 23, of West Virginia, and Michael Koon, 35, of South Carolina. The pilot, who suffered serious injuries, was Chase Olsen of Utah.

The helicopter was destroyed, according to the new report.

The three men were involved in construction on the Pierce Brook-Lewis Run Transmission Project, a 15-mile, 230-kilovolt power line between existing substations in Bradford and Keating townships. The helicopter was owned by High Line Helicopters of Virginia and was under contract to J.W. Didado Electric of Akron, Ohio.

A NTSB representative said earlier this month that it will likely be one to two years before the investigation is concluded. He said a probable cause will not be determined until the end of the investigation.

The preliminary report outlines the details of what the helicopter crew was doing.

According to NTSB’s preliminary report, on the afternoon of April 8, the three-man crew was moving a static line that was affixed above newly constructed power lines on a series of structures. The structures stood on “mountainous terrain” and included dual pole, H-frame wooden structures and single-pole steel structures, the report stated.

The static line had been attached temporarily with a wheeled pulley device, and they were re-attaching it with a more permanent device.

“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 report explained.

The two were tethered to the helicopter, Kane-based state police reported at the time of the crash.

The workers were to travel along the line from structure to structure to repeat the task.

Relating information from an interview with the pilot, the report stated, “The crew completed one structure, and the pilot hovered the helicopter into position to complete the work on the next structure.”

While the lineman was working at one structure, “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,’” the report quoted the pilot. “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,” it said.

It was at 5:11 p.m. that the aircraft — an MD Helicopters 600 N model — was destroyed due to the impact with the support structure and the ground.

At 4:53 p.m. that day, weather recorded 10 miles west of the accident site at the Bradford Regional Airport showed there was “an overcast layer at 4,100 ft, 10 statute miles visibility and wind from 290 degrees at 10 knots” — about 11.5 mph, according to the report. The temperature was about 27 degrees and the dewpoint was about 10 degrees. The altimeter setting was 29.95 inches of mercury.

The report included the pilot’s qualifications, as reported by the FAA.

The pilot had a commercial pilot certificate with ratings for rotorcraft-helicopter and instrument helicopter, and his most recent FAA second-class medical certificate was issued April 5, 2017. He had about 6,200 hours of flight experience; of that, 250 hours was in the MD 600N, and 3,000 hours working with power lines.

The 1998 helicopter had a Rolls-Royce/Allison 250-C47 series, 600-horsepower turboshaft engine and last had a 100-hour inspection on Feb. 4, the report said.

The NTSB reported that most of the wreckage was found at the bottom of the H-structure that was hit. However, the six rotor blades were scattered on the south side of the power lines; one traveled 300 feet west down the hill. The tailboom was about 70 feet west of the structure.

“The wreckage was recovered from the accident site to a secure facility for further examination at a later date,” the report stated.