CEN25FA307

The pilot and a lineman were conducting maintenance work on a powerline at the time of the accident. The operator’s chief pilot reported that the pilot had transported two linemen onto a powerline transmission tower to complete their work. The pilot then returned to pick up a third lineman. The pilot and third lineman were attempting to remove a marker ball from one of the transmission lines at the time of the accident. A barge flotilla and tow vessel were located along the south bank of the river and were stationary at the time. The helicopter was positioned above the forward portion of the barge flotilla. A witness located on the tow vessel reported that a lineman appeared to be standing on the left skid, wearing a safety harness. On the second attempt, as the pilot brought the helicopter closer to the powerline, the tail of the helicopter struck the powerline. The tailboom appeared to partially separate from the airframe with a portion of it “dangling.” The helicopter pivoted, and the cockpit hit the powerline, which created sparks similar to when an electrical transformer fails. The helicopter then fell onto the barge deck and a post-impact fire ensued. The witness did not recall seeing the helicopter on fire during flight, only the sparks when the fuselage struck the powerline. The crew of the tow vessel moved the tow vessel alongside the barge and used its pilothouse fire station to extinguish the fire. According to the chief pilot, the accident pilot and lineman had discussed accomplishing the marker ball maintenance via the helicopter platform versus utilizing a rope. The pilot had wanted to use the rope since it provided more clearance and, hence, a greater safety margin. He noted that the static line upslope was more pronounced near the transmission tower and presented more of a challenge than working farther from the tower. However, the lineman recommended utilizing the platform. Ultimately, the decision was made by the pilot to utilize the platform. The high-tension power lines spanned the river at the accident site, and the forward portion of the barge flotilla was positioned under the lines. One transmission line appeared to be frayed consistent with contact damage. The helicopter main wreckage consisted of the fuselage, engine, main rotor transmission, main rotor hub, and forward portion of the tail boom (fragmented into two sections). The aft portion of the tail boom, including the tail rotor assembly, was not present with the wreckage on the barge and likely landed in the river during the accident sequence. Each of the main rotor blades separated from the hub; two main rotor blade segments and one main rotor blade end weight were located on the barge. The remaining portions of the blades were not present and likely landed in the river. A post-impact fire consumed significant portions of the airframe. The engine remained within the engine compartment and was subjected to impact and post-impact fire damage. The compressor andturbine cases exhibited no evidence of release of high energy debris from within the engine. Visual inspection of the compressor inlet, 4th-stage power turbine wheel, and 1st-stage gas producer turbine exhibited no anomalous damage. Continuity of the compressor-to-turbine and power turbine (PT) shafts was confirmed. The interconnecting driveshaft from the engine to the main rotor transmission was fractured consistent with torsional overload. The main rotor transmission was continuous from the engine side driveshaft input outward through the tail rotor drive shaft connection. Based on the examination conducted, no evidence of a preimpact failure or malfunction was observed. However, portions of the airframe and tail rotor were not recovered from the river and could not be functionally tested. Although the autopsy revealed the presence of mild coronary artery disease, there was no forensic evidence of adverse effects or that the condition contributed to the accident. Toxicology testing did not identify any substances that might have contributed to the accident.

The video data recorder onboard the tow vessel did not record the accident sequence. Examination of the recorder revealed the most recent recording was from December 2024. Similarly, examination of a handheld GPS unit recovered from the wreckage did not contain any information relevant to the accident. The operator’s chief pilot reported that a rental main rotor transmission was installed at the time of the accident due to some metallic debris observed on the previously installed transmission chip detector. The helicopter had been issued normal and restricted category airworthiness certificates. It was operating under the normal category airworthiness certificate at the time of the accident. On August 7, 2025, about 1059 central daylight time, a Hughes (MD Helicopters) 369D helicopter, N173AL, was destroyed when it was involved in an accident near West Alton, Missouri. The pilot and crewmember were fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 133 external load flight. According to the available ADS-B data for the helicopter, the helicopter departed from the north bank of the Mississippi River about 1025. He appeared to make three trips to the powerline support tower on the south bank of the river and then returned to the original position on the north bank. The final ADS-B data point was recorded at 1035. No subsequent helicopter position data was available. The operator’s chief pilot reported that the pilot had transported two linemen onto one of the transmission towers to complete their work. The pilot then returned to pick up a third lineman. The pilot and third lineman were attempting to remove a marker ball from one of the transmission lines at the time of the accident. A barge flotilla and tow vessel were located along the south bank of the Mississippi River and were stationary at the time of the accident. The helicopter was positioned above the forward portion of the barge flotilla. A witness located on the tow vessel reported that a lineman appeared to be standing on the left skid and wearing a safety harness. On the second attempt, as the pilot brought the helicopter closer, the tail of the helicopter struck the line. The tailboom appeared to partially separate from the airframe with a portion of it “dangling.” The helicopter pivoted, and the cockpit hit the line which caused sparks similar to when an electrical transformer fails. The helicopter then fell onto the barge deck and a post-impact fire ensued. The witness did not recall seeing the helicopter on fire during flight, only the sparks when the fuselage struck the line. The crew moved the tow vessel alongside the barge and used its pilothouse fire station to extinguish the fire. A subsequent inspection of the barge did not reveal any structural damage or any release of barge contents. The Office of the Regional Medical Examiner (St. Charles, Missouri) performed an autopsy of the pilot. The pilot’s death was attributed to blunt forcetrauma sustained in the accident. The autopsy revealed the presence of mild coronary artery disease. Toxicology testing performed at the FAA Forensic Sciences Laboratory found no carboxyhemoglobin, ethanol, or drugs of abuse. Glucose (29 mg/dL) was detected in urine. No glucose was detected vitreous. Naproxen was detected in blood and urine. Sildenafil was detected in urine. Desmethylsildenafil, the metabolite of sildenafil, was detected in blood and urine. Tadalafil was detected in blood and urine. Naproxen is a non-prescription NSAID used to treat pain and inflammation. It is acceptable for pilots if the underlying condition is acceptable. Sildenafil is a prescription medication and is not typically impairing. Desmethylsildenafil is an active metabolite of sildenafil. Tadalafil is a prescription medication and is not typically impairing. The pilot’s flight time logbook was not available to the investigation. On the operator’s Annual Pilot Experience Form, dated May 20, 2025, the pilot reported helicopter flight time of 2,632 hours with 2,402 hours in Hughes 500D/E (369D) helicopters. His total flight time was also listed as 2,632 hours. The operator chief pilot estimated the pilot’s flight time within the preceding 90 days as about 250 hours. The chief pilot for the operator stated the pilot had completed training specific to flying in the wire environment in April 2024 and May 2025. According to the chief pilot, the accident pilot and lineman had discussed accomplishing the marker ball maintenance via the helicopter platform versus utilizing a rope. The pilot had wanted to use the rope since it provided more clearance and, hence, a greater safety margin. The chief pilot noted that the static line upslope was more pronounced near the transmission tower and presented more of a challenge than working farther from the tower. However, the lineman recommended utilizing the platform. Ultimately, the decision was made by the accident pilot to utilize the platform. ACCIDENT SITE The accident site was located on a barge along the south bank of the Mississippi River about 0.61 miles downstream from the Melvin Price Lock and Dam. The site was positioned under a set of high-tension power lines running across the river between Illinois and Missouri. The barge flotilla consisted of ten loaded barges. The flotilla and tow vessel were stationary at the time. The helicopter impacted the right-side (starboard) barge, three rows forward from the tow vessel. An examination by a marine surveyor revealed no immediate structural damage to the barge. The exterior coating exhibited thermal damage consistent with the fire. Helicopter debris impacted the adjacent barges resulting in minor damage to one of them. No fire damage was observed to those barges. No evidence of release of any barge contents was observed. The high-tension power lines spanned the river at the accident site, and the forward portion of the barge flotilla was positioned under the lines. The powerline support towers – one on each side of the river – were about 0.37 miles apart and were about 350 feet high. The towers supported a total of five transmission lines – three lower and two upper – and two static lines. The southeast static line appeared to be severed. Additionally, the lower, southeast transmission line appeared to be frayed consistent with contact damage. AIRFRAME EXAMINATION The helicopter main wreckage consisted of the fuselage, engine, main rotor transmission, main rotor hub, and forward portion of the tail boom (fragmented into two sections). One tail boom fragment was draped over the edge of the barge upper deck and retained by the tail rotor push-pull tube. The fuselage came to rest upright on the barge deck. The entire fuselage was affected, and significant portions were completely consumed, by the post-impact fire. One main rotor blade was located about 150 ft from the main wreckage. A 7-foot segment of a second main rotor blade was located partially on deck about 176 ft from the main wreckage. Finally, a main rotor blade tip, about 6-inches in length, was located approximately 26 ft from the main wreckage. The end weight was securely attached. The extent of the fire damage precluded a complete examination of the flight control system. Both the cyclic and collective controls were identified in the wreckage. They were both separated from the support structure and control linkage, and they were damaged consistent with impact forces and thermal exposure. The main rotor transmission was dislocated relative to the engine and exhibited thermal damage. Each of the main rotor blades was separated from the hub. Rotation of the input drive shaft produced corresponding rotation of the rotor mast and the tail rotor drive shaft. The aft fuselage was partially consumed with the firewall remaining. The engine remained in position within the aft fuselage. The tail boom was separated. Two sections – one 4 ft long and one 3 ft long – came to rest on the barge deck adjacent to the aft fuselage. Both sections exhibited thermal damage. The 4 ft section contained a segment of the tail rotor drive shaft. One section of the tail rotor control push-pull tube was continuous between both tail boom segments. The aft portion of the tail boom including the tail rotor and horizontal stabilizer were not present with the wreckage and were presumed to have landed in the river. One main rotor blade was separated and located on the barge. The blade remained secured to the fitting at the root, and the fitting was fractured, consistent with an overstress failure. The blade was distorted and torn across the entire span with localized areas of trailing edge delamination. The blade tip weight was intact. A 7-foot section of a second main rotor blade was located on an adjacent barge. The section spanned from near the root to STA 105. This blade section was similarly distorted and delaminated. In addition, it exhibited repetitive leading-edge impressions andpaint erosion consistent with contact to a powerline. A main rotor blade tip, about 9 inches in length, with the tip weight attached, was located on the barge. It could not be determined if this blade tip was from the same blade as the 7-foot blade segment or from a different blade. The remaining main rotor blades were not present with the wreckage and were presumed to have landed in the river. A search of the river bottom in the vicinity of the accident site using side-scan sonar equipment did not locate the missing portion of the tailboom or the main rotor blades. ENGINE EXAMINATION The engine remained within the engine compartment and was subjected to impact and post-impact fire damage. Extensive smoke, soot, and thermal damage were present on the exterior of the engine. The compressor and turbine cases were intact and exhibited no evidence of release of high energy debris from within the engine. The accessory gears, to the extent they were visible through the partially consumed housing, appeared intact and in position. The gas producer (N1) and power turbine (N2) rotors could not be rotated by hand. Visual inspection of the compressor inlet, 4th-stage power turbine wheel, and 1st-stage gas producer turbine exhibited no anomalous damage. Continuity of the compressor-to-turbine (CT) shaft and the power turbine (PT) shaft was confirmed. Both components, including the splined sections, appeared intact, and were engaged to the mating splined components upon disassembly. The interconnecting driveshaft from the engine to the main rotor transmission was fractured consistent with torsional overload. The main rotor transmission was continuous from the engine side driveshaft input outward through the tail rotor drive shaft connection. The examination revealed no evidence of a pre-impact failure or malfunction of the engine.