Accident Overview
On August 7, 2021, about 1800 eastern daylight time, an experimental amateur-built Rotorway Exec 162F, registration N162KJ, was destroyed in an accident in Argyle, New York. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot and passenger sustained fatal injuries.
Witness Account
A witness located about half a mile north of the accident site observed the helicopter flying southbound at an estimated altitude between 50 and 75 feet above ground level. The witness reported that the helicopter appeared to be having issues, as it could not maintain altitude. The witness described the flight as appearing to bounce as it crossed a field. Shortly after the helicopter flew over a tree line, the witness heard a loud sound and saw the rotor stop. The helicopter then fell straight down. A postimpact fire ensued.
Pilot Information
Examination of the pilot's records revealed that he did not possess a rotorcraft-helicopter rating. His logbook contained two endorsements for solo flight, each valid for 90 days, with the most recent endorsement expiring in June 2004. His most recent valid medical certificate was issued in 2000. In 2016, the Federal Aviation Administration (FAA) denied his application for medical certification due to a medical history that included bipolar disorder and depression. The pilot completed the build of the helicopter in May 2003.
Wreckage Examination
Postaccident examination of the accident scene revealed a debris path approximately 400 feet long, oriented on a magnetic heading of 210 degrees. The debris path began in an open field of 4-foot-tall grass with a fractured piece of aluminum skin from the right side of the tailboom, just forward of the tail rotor arc. The right horizontal stabilizer was located 156 feet along the debris path, 70 feet left of the path centerline. The left horizontal stabilizer was found about 10 feet farther along the path and 205 feet left of centerline.
A 4-foot-long section of the aft end of the tailboom, including the vertical stabilizer and the tail rotor gearbox with one tail rotor blade attached, was located 30 feet farther down the path, 10 feet left of centerline, just after the path transitioned from the grass field to the tree line. An impact mark on the right side of this tailboom section, near the fractured forward end, was consistent in size and shape with the profile of a main rotor blade. The wreckage path continued for another 200 feet through the woods and down a steep hill, with numerous fragments of clear plastic canopy scattered along and to the sides.
The main wreckage, located at the end of the path, came to rest on its right side and top, almost completely inverted. It was largely consumed by the postimpact fire. Molten aluminum remnants were present beneath the main wreckage. No ground scars were observed leading up to the main wreckage, and trees and foliage along the wreckage path showed no damage except for broken branches directly above and immediately surrounding the main wreckage.
Control System Examination
Control continuity was established from the anti-torque pedals to the tail rotor through breaks in the push-pull cable. Continuity from the cockpit controls to the teetering main rotor head was partially established; several components in the push-pull cable system were not found.
Rotor System Damage
Both main rotor blades were intact and attached to the blade grips, and both exhibited downward bending damage in several locations. The teetering hinge attach points were fractured on both sides of the hub plate. One rotor blade had leading-edge damage and gouging about 1 to 2 feet inboard of the blade tip. Both pitch change links were fractured at their upper rod ends, and both links remained attached to fractured segments of their lower control horns. The inboard ends of both lower blade grips were bent upward, and each had semicircular deformation consistent with the diameter of the rotor mast.
Toxicology Findings
Toxicology testing by the FAA Forensic Sciences Laboratory detected ethanol in the pilot's blood; no ethanol was detected in his urine. N-propanol, a microbial product, was detected in his blood. Diphenhydramine, trazodone, and 7-aminoclonazepam (the inactive metabolite of clonazepam) were detected in his blood and urine. Delta-9-tetrahydrocannabinol (THC), 11-hydroxy-delta-9-THC, and carboxy-delta-9-tetrahydrocannabinol were also detected in the pilot's blood and urine.
FAA Guidance on Substances
According to the FAA, diphenhydramine and trazodone (used to treat depression, anxiety, and insomnia) are both sedating but can be acceptable for use if taken with sufficient waiting periods before flying; trazodone is disqualifying if used to treat bipolar disorder. Clonazepam is disqualifying due to the underlying condition it treats (panic disorders). The use of marijuana is addressed by 14 Code of Federal Regulations 91.17(a)(3), which states that no person may act as a crewmember while using any drug that affects faculties contrary to safety.
Helicopter Aerodynamics Reference
The FAA's Helicopter Flying Handbook describes low-G conditions and mast bumping for helicopters with two-bladed teetering rotors. It states that such helicopters rely entirely on the tilt of the thrust vector for control, making low-G conditions potentially catastrophic. Abrupt forward cyclic input or pushover at moderate or high airspeed can cause a low-G condition, reducing thrust and leading to loss of fuselage attitude control. Tail rotor thrust or other aerodynamic factors can induce a roll. If the pilot applies cyclic to correct, the combination of fuselage angle and rotor disk angle may exceed hub clearances, resulting in hub contact with the rotor mast, known as mast bumping. This can sever the mast or allow rotor blades to strike the tail or other parts of the helicopter.