History of Flight
On November 28, 2021, about 1658 central standard time, a Bell 206B helicopter, N59600, was destroyed when it was involved in an accident near Perry, Oklahoma. The commercial pilot sustained fatal injuries and the passenger, who held a student pilot certificate, sustained serious injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The passenger, the pilot's son, reported that the pilot preflighted the helicopter at 1530. The helicopter was kept in a barn on the pilot's property. Nothing abnormal was noted during the preflight. During the preflight, the pilot installed the flight controls for the left seat position. Both front doors were installed for the flight, and neither occupant filmed during the flight. The pilot, seated in the left seat, wore a surplus US Army SPH-4 flight helmet without a tinted visor and no sunglasses. The passenger in the right seat wore a headset and no sunglasses.
The helicopter departed from the property about 1600 with about 50 gallons of fuel. At the time of the accident, about 25 gallons remained. The helicopter flew to Perry Municipal Airport (F22) and performed three traffic pattern circuits. Then it departed west of I-35, where the pilot intended to demonstrate low-level aerial application maneuvers. The setting sun was in both occupants' eyes during this time.
The pilot performed several low-level east-to-west maneuvers about 15 feet above ground level at 60 knots. During a pass to the east, both occupants observed a coyote in a large field in tall grass near a barbed wire fence. The pilot executed a right pedal turn to look at the coyote. The helicopter transitioned to an out-of-ground-effect hover, facing south, about 40 feet above ground level. While both occupants were looking at the coyote, the helicopter began an uncommanded left roll.
The passenger could not determine cyclic positions during the roll. The accident sequence occurred very fast; the pilot was on the controls throughout and the passenger was not operating them. The pilot made no announcements. The helicopter did not spin, and the passenger did not recall the main rotor striking the ground before impact. No vibrations, alarms, or warning lights were noted. The helicopter impacted a grass field just south of the barbed wire fence.
Grasses around the helicopter ignited immediately after impact. The passenger extracted himself and the deceased pilot from the wreckage, and about five minutes later the wreckage caught fire and was destroyed. The passenger contacted first responders. No known witnesses observed the accident sequence.
Personnel Information
The pilot, owner of the helicopter, worked full-time as a helicopter air ambulance pilot and part-time as a Part 137 aerial application pilot and rancher. His personal logbook was not available; air ambulance company records were reviewed. He did not hold a mechanic certificate. The passenger was enrolled in a university aviation program learning to fly helicopters.
Aircraft Information
The helicopter was certificated in standard and restricted airworthiness categories. The pilot purchased it in November 2013. It was modified with a Simplex 4900 aerial application spray system per a supplemental type certificate; spray booms were not installed at the time. The helicopter was equipped with a Satloc unit and a Shadin Fuel Flow Indicator, but the Satloc was destroyed and the Shadin unit not identified. No crash-resistant fuel system was installed, nor required. An emergency locator transmitter was not identified. Airframe and engine maintenance records were unavailable.
Meteorological Information
The passenger reported no wind, no turbulence, and clear visibility. Meteorological data indicated a light southerly wind below 2,000 feet, no turbulence or low-level wind shear, and a pilot report of 10 miles visibility. No inflight weather advisories were in effect. The accident occurred before sunset with a low sun elevation. Density altitude at the site was estimated at 931 feet above mean sea level.
Wreckage and Impact Information
The accident site was a cattle pasture at 1,056 feet elevation. The barbed wire fence near which the helicopter came to rest was intact with no impact damage; it was cut later for access. All major structural parts were accounted for. Most of the forward and intermediate fuselage was consumed by fire. The tailboom detached from the intermediate fuselage and was found near the main wreckage. The main rotor hub and blade assembly remained attached to the fractured mast. Both main rotor blades had fracturing and bending. The transmission was partially consumed; main rotor drive continuity could not be established. The tail rotor drive system was continuous within the tail boom. The tail rotor gearbox separated but rotated freely without binding or abnormal sounds.
Fuel system components, including the bladder, boost pumps, and lines, were destroyed by fire. Hydraulic system components, including the pump and servo actuators, were destroyed; three servo actuators were retained for examination. Flight control components—collective, cyclic, and tail rotor controls—were destroyed by fire. One collective stick and one pedal assembly were present, but cyclic controls were not located. Flight control continuity could not be established due to thermal damage. The hopper was destroyed; no evidence of chemicals being carried. The cockpit structure, dash panel, seats, and restraints were destroyed. No gauge readings were obtained. Fuel samples were unavailable.
The turboshaft engine was securely mounted; all sections suffered fire damage. The second, third, and fourth stage turbine wheels were undamaged. The turbine-to-compressor coupling was intact. A silver powder-like substance consistent with compressor diffuser coating was observed, supporting engine operation at impact. Postaccident analysis of fluid from the servo actuators found a mixture of petroleum and synthetic hydraulic fluid with an unknown component; the passenger did not know if fluid was added. Examination of the servo actuators revealed no mechanical malfunctions or failures that could cause a cyclic hard over.
Additional Information
The task of installing and removing copilot flight controls is described in the Bell 206 maintenance manual. Bell issued Operations Safety Notice 206-84-12 in 1984, citing a previous accident caused by improperly installed copilot cyclic stick. Bell later released Alert Service Bulletin 206-85-27 with design changes to the quick-disconnect kit. Compliance with these bulletins is not mandated for Part 91 or Part 137 operations. Maintenance records were unavailable to determine if the bulletin was complied with. At the time of the accident, no clear guidance existed for Part 91/137 operators on flight control installation and removal. Bell declined to publish such guidance when requested by the NTSB.
The FAA-approved rotorcraft flight manual contained no guidance for pilots in the event of a flight control malfunction. Bell declined a request to publish emergency procedure guidance.
The FAA has published a Fly Safe Fact Sheet on startle response, describing how unexpected emergencies may delay or initiate inappropriate actions.
Flight Recorders
The helicopter was not equipped with a crashworthy flight data recorder or cockpit voice recorder, nor required to be.
Medical and Pathological Information
At his most recent FAA medical examination, the pilot reported no medications or medical conditions. Autopsy determined cause of death as multiple blunt force injuries, manner accident. The pilot had 90% stenosis of left anterior descending and right coronary arteries. Toxicology identified acetaminophen in femoral blood and urine. The passenger's toxicology detected THC in urine at 1.7 ng/mL but not in blood; 11-OH-THC in urine not quantified; THC-COOH in hospital admission blood at 23.4 ng/mL and urine at 84.1 ng/mL.