SEA04TA163

The reversal of the reel machine during a sock line pull which resulted in a loss of control while hovering out of ground effect. Factors were the failure of company management to develop adequate procedures for conducting sock line pulls, the inadequate communication between the chief pilot and the pilot, the inadequate communication between the ground personnel and the pilot, and the pilot's lack of recent experience in Class C external load operations.

The helicopter was pulling sock line (rope) that was to be used to install a static wire at the top of 220-foot-tall towers supporting a 500-kV power line. (The stringing of sock line is a Class C external load operation, meaning an operation in which the external load is jettisonable and remains in contact with land or water during the rotorcraft operation.) The sock line was attached to the helicopter's remote cargo hook and played out of a truck mounted reel machine operating in the power payout mode. The reel machine operator stated that "suddenly the rope wrapped over another rope or pulled down in the drum, causing the rope to reverse on the drum." The reel machine operator immediately moved the machine's shift lever from "OUT" to "NEUTRAL," but by the time he had accomplished this, the rope between the reel and the helicopter went taut. Numerous witnesses, who were all members of the line crew installing the wires, reported that when the rope went taut, the helicopter pitched up and rolled right. The helicopter descended, impacted the ground and came to rest on its right side. Post-accident interviews revealed that the pilot, the line crew, and company management did not adequately recognize and mitigate the risks inherent in the procedures they were using to conduct the sock line pull. Specifically, the rigging used was a 25-foot long line with a 31-pound ballast weight, while other operators pulling sock line use longer long lines (50 to 100 feet) and heavier ballast (150 to 300 pounds) in order to provide pilots with an earlier warning of an impending shock load due to a snag so that the pilot will have more time to respond. Additionally, at the pilot's request, the reel machine was being operated in the power payout mode, instead of the free wheeling mode. This was due to a miscommunication between the pilot and the chief pilot, who stated that when he discussed the operation with the pilot, he assumed the pilot understood that he intended for the reel to be freewheeling. In the freewheel mode, when a snag occurs, at worst, the reel stops. In the power payout mode, when a snag occurs, the line can double back on the reel and begin to pull back in, as occurred in this accident. Also, while preparing for the sock line pull, the line crew was paying out sock line on the ground and experienced a snag, which resulted in the line being pulled in instead of paying out, just as occurred in the accident. However, there was no communication of this occurrence to the pilot. Finally, although the pilot had 21,803 hours rotorcraft flight time, 16,000 hours in the accident make and model helicopter, and 4,000 hours conducting external load operations, his most recent Class C external load experience was 5 years and 3 months prior to the accident.

On August 17, 2004, at 0940 Pacific daylight time, a Bell 206B helicopter, N34698, was destroyed when it impacted terrain following a loss of control while hovering out of ground effect with an external load near Mead, Washington. The airline transport pilot, the sole occupant, was fatally injured. The helicopter was registered to and operated by the United States Department of Energy (DOE). The purpose of the public use flight conducted under Title 14 CFR Part 133 was to assist in stringing power lines for the Bonneville Power Administration (BPA). Visual meteorological conditions prevailed, and a company flight plan was filed. The flight departed from Spokane International Airport in Spokane, Washington at 0655. INFORMATION FROM FAA According to information gathered by FAA inspectors who responded to the accident site, the helicopter was pulling sock line (rope) that was to be used to install a static wire at the top of 220-foot-tall towers supporting a 500-kV power line. (The stringing of sock line is a Class C external load operation, meaning an operation in which the external load is jettisonable and remains in contact with land or water during the rotorcraft operation.) The sock line was attached to the helicopter's remote cargo hook and played out of a truck mounted reel machine. The reel machine operator provided a written statement to the FAA inspectors stating that "suddenly the rope wrapped over another rope or pulled down in the drum, causing the rope to reverse on the drum." The reel machine operator immediately moved the machine's shift lever from "OUT" to "NEUTRAL," but by the time he had accomplished this, the rope between the reel and the helicopter went taut. Numerous witnesses, who were all members of the line crew installing the wires, reported that when the rope went taut, the helicopter pitched up and rolled right. The helicopter descended, impacted the ground and came to rest on its right side. A small fire erupted near the engine compartment, which the line crew extinguished with their fire extinguishers. They then used a winch to raise the helicopter upright to gain access to the cabin and render first aid. Examination of photos and a diagram provided by the FAA inspectors revealed that the 500-kV power line was oriented east-west, and the helicopter was pulling the sock line from the east towards the west. The helicopter came to rest about 700 feet west of the reel machine, near the base of a 13.8-kV power line that ran perpendicular to and beneath the 500-kV power line. One of the wooden towers supporting the 13.8-kV power line was damaged. Pieces of the wooden cross arms were broken off the tower, and there was evidence of a main rotor blade strike to one of the tower's poles about 18 feet agl. The right side of the helicopter's fuselage was crushed inward. The main rotor system, the vertical fin, the forward cross tube, the left skid, and one tail rotor blade were separated from the helicopter. All of the damage to the helicopter appeared to be impact related. The helicopter's 25-foot long line was severed about 5 feet below the helicopter's belly hook. The shackle on the upper end of the long line was still attached to the belly hook; however, the long line's electrical plug was disconnected from the mating plug on the belly of the helicopter. The other section of the long line ending with the remote hook to which the sock line was still attached was found hanging from a chain link fence about 70 feet east of the helicopter. INFORMATION FROM DOE Personnel with the DOE conducted witness interviews, examined the accident site, and prepared a report of their observations. According to the DOE report, the helicopter was being used to string sock line to enable the subsequent stringing of new conductors and static wire on the 500-kV power line. The helicopter was needed in order to pass the sock lines over nine energized power lines that crossed under the 500-kV line. (These nine energized power lines were in addition to the 13.8-kV line described above which was de-energized.) The sock line would later be used by the line crew to pull the heavier conductors and static wires. The first part of the job involved pulling sock line from a triple drum puller/tensioner (reel machine) for the three conductor wires. The second part of the job involved pulling sock line from a single drum puller/tensioner for the two static wires. Interviews conducted by DOE personnel revealed that on August 12, 2004, the pilot met with the line crew to discuss the sock line pull. The triple drum operator and the pilot discussed the operation of the puller/tensioners and whether to free-wheel or power payout the sock line. The pilot indicated that he had been told by the BPA Chief Helicopter Pilot that as long as the line would come off the reel at a fast walking pace, it would be adequate for the operation. The triple drum operator paid out the sock line under power from the triple drum puller as the pilot walked with it at a fast pace. As a result of this test, the pilot was satisfied with the speed of power payout. This test was not repeated with the single drum puller. The Chief Pilot later reported to the DOE investigators that he intended the reel to be freewheeling and assumed the pilot understood this. The DOE report noted that in the freewheel mode, when a snag occurs, at worst, the reel stops. In the power payout mode, when a snag occurs, the line can double back on the reel and begin to pull back in. On August 16, 2004, the pilot and the line crew attended an in-depth briefing of the work at a "tailboard" meeting. The tailboard meeting included a helicopter safety briefing given by the job foreman that covered ground crew safety. According to the DOE report, the helicopter briefing did not include a general discussion of "such topics as how to respond to emergency situations like sock line hang-ups, other hazards specific to Class C loads, or other detailed helicopter operational procedures." However, conversations between the pilot and individual crewmen took place during which some of these issues were discussed. Witnesses interviewed by the DOE investigators reported that the helicopter landed at the work site about 0700 on the day of the accident. The pilot shut down the helicopter and attached a 25-foot long line with a 31-pound ballast and remote cargo hook to the helicopter's belly hook. The pilot and one of the linemen (a heavy mobile equipment mechanic) physically checked the range of motion in all directions of the belly hook with the long line attached to ensure that it would not interfere with the remote hook's electrical connection at the belly of the helicopter. The pilot and a lineman then tested the remote hook to ensure that it operated electrically and mechanically. Later examination of the helicopter by the DOE investigators revealed that the pilot did not wrap electrical tape around the remote cargo hook's electrical connection at the belly of the helicopter. The investigators found that there was no written requirement in the BPA Aircraft Services External Load Manual to perform this task. They noted that experienced pilots conducting external load operations commonly take this precaution to prevent inadvertent disconnection of the remote hook's electrical connection, which disables the pilot's remote cargo hook electrical jettison switch. (The remote cargo hook electrical jettison switch is one of three methods the pilot can use to jettison an external load. The other two methods are the belly hook electrical jettison switch and the belly hook manual release handle.) Prior to commencing the work, the pilot discussed the use of the triple drum puller with an equipment operator. Approximately 0850, the helicopter began the conductor sock line pulls from the triple drum puller with the puller in the power payout mode. These thr