N5187SHughes 369D · 1982

On October 2, 2018 about 1315 central daylight time, a Hughes 369D helicopter, N5187S, was destroyed when it was involved in an accident near McDougal, Arkansas. The pilot was fatally injured, and the two linemen sustained minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 133 external load operation.

The helicopter had departed from a grass landing zone after a lunch break with two linemen tethered to the helicopter for short haul operations in connection with utility line work to decommission power line structures.

Figure 1: Main Wreckage and Landing Zone Locations

One of the linemen stated he was in communication with the pilot via a Bluetooth communication system to coordinate his placement on the utility pole. The pilot was hovering the helicopter next to the power line structure when they heard a "loud boom" and "metallic crunch" and the crews' short haul lines were released from the helicopter. The helicopter descended and impacted the ground beneath the structure.

The lineman stated that the pilot typically had a calm demeanor during operations; however, before the pole strike, the pilot was not calm and hesitated in responding to the lineman's communications. The lineman said the helicopter was "getting choppy and moving around a lot" when he was attaching to the utility pole, but he did not look up at the helicopter. He could see the helicopter shadow on the ground and saw the tail "darting around."

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Note: Re-registration of the helicopter from N5187 to N454AR was pending with the Federal Aviation Administration (FAA), however, the tail number had already been repainted to reflect the new registration.

The area surrounding the accident site was documented using official Meteorological Aerodrome Reports (METARs) and Specials (SPECIs).

Figure 5: Sectional chart of accident area with the location of the accident site and the closest surface observation site.

Observations from the two closest airports to the accident site, around the accident time, indicated visual flight rules conditions; however, the winds increased in magnitude with gusts to 19 knots out of the southwest.

At K4M9, weather at 1315 CDT, automated, wind from 250° at 12 knots. At 1335 CDT, automated weather at K4M9 was wind from 240° at 10 knots with gusts to 17 knots. At KPOF weather at 1253 CDT, automated, wind from 220° at 11 knots. At 1353 CDT, automated weather at KPOF was wind from 220° at 14 knots with gusts to 19 knots.

The closest weather surveillance radar located in Memphis, Tennessee, indicated reflectivity values between 20 and 34 dBZ moved from west to east above the accident site at the accident time. These reflectivity values corresponded to light to moderate precipitation and occurred at the same time as the wind gusts increased to 17 knots at Corning Municipal Airport at 1335, which was located 10 miles west-southwest of the accident site. There were no lightning flashes around the accident site at the accident time.

Based on information from one of the linemen, the accident pilot checked the weather conditions before the flight, but it is unknown which weather products the pilot checked. A search of archived ForeFlight information indicated that the accident pilot did not review or request any weather information from ForeFlight. It is unknown if the accident pilot checked or received additional weather information during the accident flight.

Note: Re-registration of the helicopter from N5187 to N454AR was pending with the Federal Aviation Administration (FAA), however, the tail number had already been repainted to reflect the new registration.

The main wreckage came to rest on the north side of wooden and steel utility pole structures in a muddy soybean field. This area of the field was flooded with about 2 ft of water at the time of the accident due to heavy rains prior to the accident. The helicopter impacted the ground on the right side; the damage was consistent with nearly vertical forces. The main wreckage included the fuselage, left skid and rear strut, right rear strut, main rotor drive shaft, and engine. All five main rotor blades, the tail rotor section, tail boom, and right skid were found in the area surrounding the main wreckage.

Figure 2: Main Wreckage

Before impacting the ground, the helicopter's main rotor blades impacted the top of the steel utility pole. A drone was used to observe the impact damage and showed an inward indentation in the top of the pole, as shown in Figure 3. The tower cap plate was separated and about 3/4 of the plate was submerged in water. There was a gash in the side of the plate, as shown in Figure 4.

Gash in the Side of Cap Plate Platelate

Impact Damage from Main Rotor Blade

Figures 3 and 4: Photograph of Impact of Top of Steel Utility Pole and Cap Plate with Impact Mark

A postaccident examination of the helicopter revealed no mechanical anomalies that would have precluded normal operation.

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The State Crime Laboratory, Little Rock, Arkansas, performed an autopsy of the pilot. The cause of death was multiple traumatic injuries and drowning, and the manner of death was accident.

Toxicology testing performed by the FAA Forensic Sciences Laboratory detected the sedating antihistamine diphenhydramine at 0.037 micrograms per milliliter (µg/mL) in the pilot's blood; diphenhydramine was also detected in urine. Diphenhydramine (commonly marketed as Benadryl) is available over the counter in products used to treat colds, allergies, and insomnia. The therapeutic range is 0.025 to 0.100 µg/mL. Diphenhydramine undergoes postmortem distribution and central levels may be two to three times higher than peripheral levels.

Tramadol (commonly marketed as Ultram) was detected in cavity blood at 0.058 µg/mL; tramadol and its active metabolite O-desmethyltramadol were detected in the pilot's urine. Tramadol is an opioid analgesic used to relieve moderate to severe pain. Tramadol carries the warning that it may impair mental or physical ability required for the performance of hazardous tasks. The therapeutic range for tramadol is 0.05 to 0.50 µg/mL in blood. Tramadol undergoes postmortem redistribution and there is a high degree of inter-individual variation in its distribution in the body.

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