N571HHHughes Helicopters HUGHES 369D · 1977

On January 11, 2018, about 1350 Atlantic Standard Time, a Hughes 369D, N571HH, operated by High Line Helicopters LLC. (HLH), was not damaged during an external load operation near San Juan, Puerto Rico. The commercial pilot was not injured, while one power line maintenance person was seriously injured. The external load flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 133. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight.The pilot reported to the U.S. Army Corps of Engineers (USACE) that the plan for the day was to install six polymer insulators and wire to utility towers. The flights originated from a landing zone, where different equipment could be added and removed from the helicopter throughout the day. During the day, the pilot used the helicopter to lift ladders with ground crewmen on them nine times. The common terminology used during radio transmissions for that specific task was "man pick with a ladder," which alerts the pilot to use an A-frame attachment at the end of the longline, instead of a grapple. After making nine "man picks with a ladder" using the A-frame, he was summoned back to the utility tower with a 100-foot longline and grapple to move a wire up to the middle arm of the tower. After doing so, a transmission came over the radio to move a ladder with the grapple and 100-foot longline.

The terminology used during that transmission was "ladder pick," which alerts the pilot that the A-frame is not required as it would be a gear move only. From the pilot's position, he was able to see a lineman down near the bottom arm and another lineman near the top arm of the utility tower. The pilot flew into position to pick up the ladder only. He witnessed the lineman at the top arm rig the grapple. After the pilot received a visual signal from the lineman near the top arm, he began to maneuver the helicopter to apply upward pressure. Shortly after this, the ladder appeared to become bound on something. At that point the pilot could see both lineman shaking the ladder back and forth to get it free. Directly following this action, the lineman near the top arm reached out for the right-side safety chain on the ladder to remove it. Following that action, the ladder pivoted, came free of the structure and grapple, and the lineman and ladder fell to the ground.

In a subsequent statement provided to the National Transportation Safety Board, the pilot reported that as the ladder became bound, the upper (accident) lineman gave a visual head signal to let the line down (shaking head left to right). The pilot then lowered the line until the grapple came free of the rigging and was suspended near the upper lineman, but not in contact with the ladder or any other rigging. As the pilot hovered above, both lineman were shaking the ladder in an attempt to free it. Immediately after, the upper lineman reached out for the right-side safety chain on the ladder in an apparent attempt to remove it. When he did so, the ladder pivoted to the right, came free of the structure and the lineman and ladder departed the structure and fell to the ground.

The accident lineman reported to the USACE that a conductor was positioned low and hard against the utility tower at an angle, which necessitated the helicopter to use a longer line to lift it up. The helicopter then had to maneuver at an extreme angle to pull the conductor away from the tower, but could not maneuver the conductor around the ladder. The pilot radioed the accident lineman and stated that he was going to attempt the lift again, but with a shorter line. The accident lineman then told the pilot that he wanted to move the ladder to the other side of the tower to provide more clearance to lift the conductor. The helicopter returned with the A-frame, and picked up the ladder with the accident lineman on it and moved it directly above where it had been. However, that was not where the accident lineman wanted the ladder, but he was not in radio contact with the helicopter at that time (the radio was working properly, but at that time he was using both hands to safety/unsafety himself and/or the ladder to the structure).

The helicopter returned with the grapple at the end of the long line and the accident lineman advised the pilot that he thought the ladder would have to be positioned on the other side of the tower to provide enough clearance. At that point, the helicopter pilot lowered the grapple down and did not go back to get the A-frame. The accident lineman hooked the grapple to the ladder and unsafetied the ladder from the tower. The helicopter then picked up the ladder with the accident lineman on it and successfully moved it to the other side of the tower. Subsequently, the helicopter pilot moved the conductor and returned to the ladder with the grapple. The accident lineman hooked the grapple to the ladder, but before he could unsafety the ladder from the tower, the helicopter pilot tried to lift the ladder with the accident lineman on it. The accident lineman then gave a down signal and was trying to get the safety undone. The accident lineman was able to disconnect the safety; after which the top of the ladder tipped over and the ladder and lineman descended to the ground.

Another lineman was partnered with the accident lineman throughout the day. He reported to the USACE that they had worked on a different tower earlier in the day. During that work, the helicopter pilot completed some tasks with the grapple and then lifted the ladder with the accident lineman to a different location on the tower with the grapple, rather than an A-frame. However, in that instance, the ladder was only being moved straight down to a different position on the tower. When the helicopter departed, the other lineman mentioned to the accident lineman that he was surprised that they could use the grapple to move the ladder with a lineman on it and they briefly discussed it. Later in the day, while working on the accident tower, the accident lineman told the helicopter pilot that he needed the ladder further away from the conductor. The helicopter pilot did not go back to get the A-frame and moved the ladder with the accident lineman, using a 50-foot line with a grapple, directly above where it had been.

The pilot subsequently instructed the accident lineman that he needed to move the ladder to the opposite side of the tower. The helicopter successfully moved the ladder with the accident lineman to the other side of the tower with the grapple. After the helicopter lifted the conductor up on top of an arm with a grapple, the accident lineman hooked the grapple to the ladder and the helicopter started to lift the ladder with the accident lineman on it; however, the second safety was still attached from the tower to the ladder. It seemed like it took about 1 minute for the accident lineman to free the second safety. When the helicopter lifted the ladder, it went up, then backwards and downwards at an angle before falling to the ground with the accident lineman on it.

Review of two videos provided by an eyewitness revealed that about 40 minutes prior to the accident, the helicopter lifted a cable with a grapple. About 20 minutes prior to the accident, the helicopter lifted a ladder with a lineman on it from a lower static arm to an upper static arm on the same side of the tower, using an A-frame.

Review of a video recorded by the accident lineman earlier that day revealed that the accident lineman was on a ladder and used hand-signals to the helicopter. The ladder was then lifted with a grapple, with the lineman on it, and subsequently placed on a lower static arm.

Review of the USACE Accident Report revealed the "direct cause" of the accident was: "Failure to follow written safety procedures…Grapple hook was used instead of A Frame which is approved for human transport. This does not follow flight rules for human transport or the written safety policies in company safety manual."

Review of the electrical contractor accident report revealed the "direct cause" of the accident was: "…The individual's failure to follow the written procedures for the transport of human cargo by both the helicopter pilot and both lineman resulted in Lineman 1's fall from the helicopter. The use of a grapple hook for human external cargo (HEC) is not allowed in the (HLH) safety manual. Lineman 2 observed this procedure being violated while working on the first pole but did not stop the work. Lineman 1 and (the pilot) both violated this procedure at least two times on poles 1 and 2."

In addition, the report noted that both linemen were wearing a bee suit due to the presence of bee nests and neither linemen had previous performed this work while wearing a bee suit.

Review of Federal Aviation Regulation 27.865 (c) (2) and (4) revealed the for rotorcraft-load combinations to be used for human external cargo (HEC) applications: "Have a reliable, approved personnel carrying device system that has the structural capability and personnel safety features essential for external occupant safety…Have equipment to allow direct intercommunication among required crewmembers and external occupants…" The pilot must use approved attaching means during external load HEC operations and an intercom system, not radio, is required during external load HEC operations.

The 1356 weather observation at Luis Munoz Marin International Airport, located about 15 nautical miles northwest of the accident site included wind at 17 knots, gusting to 23 knots, a temperature of 29°C (84°F) and a dew point of 21°C (70°F).