History of Flight
On September 27, 2022, at about 1015 central daylight time, an Airgyro AG915 Spartan gyroplane, registration N499AG, was destroyed when it impacted terrain near Yankton, South Dakota. The pilot sustained fatal injuries. The gyroplane was operating under Title 14 Code of Federal Regulations Part 91 as a flight test. According to the pilot's family, the purpose of the local flight was to build flight time and achieve 40 flight hours on the experimental gyroplane. The aircraft was based at a hangar at Chan Gurney Municipal Airport (YKN) in Yankton, South Dakota. It departed from runway 31 and flew west.
A witness observed the gyroplane at about 400 feet above ground level (agl) emitting heavy black smoke. The gyroplane was flying west, then made a quick turn toward the south, went straight down nose first, and impacted the ground. The witness did not see any fire while the gyroplane was airborne. A second witness saw the gyroplane at about 350 ft agl, also observed a lot of black smoke, and reported a similar nose-first descent after a turn to the south.
The gyroplane struck a flat grass field on private property, approximately 2.3 nautical miles northwest of the departure end of runway 31 at YKN.
Personnel Information
The pilot was the builder of the gyroplane and, according to family, was self-taught in the build process. The pilot did not report any mechanical concerns to family members. Federal Aviation Administration (FAA) records indicated the pilot did not hold a mechanic or repairman certificate, nor was one required. The pilot's logbook was not available for review.
A pilot and mechanic who administered a builder's assistance program for experimental aircraft stated that the pilot spent about six weeks at his facility in Paris, Texas, with the gyroplane. He described the pilot as an "excellent craftsman" who performed "very good" work.
Aircraft Information
The gyroplane was built by the pilot. According to FAA airworthiness records and maintenance records, the pilot also performed maintenance as a listed repairman. The last two maintenance entries were on September 24, 2022, at which time the gyroplane had accumulated 37.8 flight hours. Those entries included replacing the engine oil drain plug and checking for oil leaks, and servicing the engine oil, replacing the oil filter, and checking for oil leaks. No uncorrected mechanical discrepancies were noted.
The gyroplane's weight and balance records were not available. The flight manual was not available because the gyroplane had not completed the required 40 flight test hours. The program letter to the FAA listed YKN as the geographical area for flight testing.
An experimental Rotax 915 iS3 engine was installed. It was partially configured for a constant speed propeller but lacked additional components, including a propeller governor. The Rotax factory installs a protective flange cover on the propeller governor pad for transportation; this cover is intended to be removed before flight. Rotax documentation states that the governor flange cover must be replaced with a functional governor or the engine converted to an iS2 version before operation. The accident engine operated as an iS3 version without a governor and without the necessary conversions.
The kit manual used to build the gyroplane (by MBL Classics – Gyroplane Department) did not specify anything about the governor flange cover, but it referenced the Rotax 915 Series Engine Installation Manual multiple times. The builder's assistance program administrator did not recall any conversations or work regarding the cover or engine conversion.
Wreckage and Impact Information
A postimpact fire consumed the composite airframe. Flight control and airframe-to-engine control continuity could not be established due to thermal damage. Four round weights (each 10 pounds, total 40 pounds) were found. The two main rotor blades were accounted for but sustained impact damage. The main rotor head, with blade remnants, was found forward of the main wreckage and could be rotated by hand with no binding.
The engine sustained thermal damage; the propeller was destroyed. Composite components showed signs of thermal damage not related to the postimpact fire. Fluid consistent with oil was found on both interior and exterior of several fuselage and empennage pieces, with patterns on exterior surfaces consistent with airflow direction.
The main rotor mast exhibited thermal discoloration and heavy sooting up to the swash plate. Remaining main rotor blade sections showed no thermal damage. The engine had oil coating over large exposed surfaces. The governor pad was heavily coated in oil, with coagulated oil beneath it. The governor oil pressure feed line banjo bolt was found finger tight, with no torque paint evidence (though paint may have been thermally damaged).
Examination revealed no governor installed on the governor pad; the governor flange cover was still in place. The cover plate bolts were finger tight. The only area not oil-covered was near the turbocharger and two exhaust ducts, which also exhibited thermal discoloration. Two aluminum valve covers (cylinders 2 and 4) collocated there were melted along the bottom edge with material flow consistent with an upright in-flight position. The oil return connection flange above the turbocharger had thermal damage and melted threads; the connector was separated from the engine. The cold side of the turbocharger and other aluminum components were also melted.
Medical and Pathological Information
An autopsy performed by the Minnehaha County Coroner (Sioux Falls, South Dakota) determined the cause of death was blunt force injuries and the manner of death was accident. No soot was found in the pilot's airways.
Additional Information
The FAA Advisory Circular 90-89C discusses flight test plans and the requirement for a minimum of 40 flight hours when a non-type-certificated engine or propeller combination is installed. The Experimental Aircraft Association's June 2023 article "The Top Five Build Errors" provides guidance on following directions, seeking expert review, being patient, and using checklists. The FAA's Aviation Maintenance Technician Handbook discusses the "dirty dozen" human factors, including the potential for catastrophic results from a lack of knowledge.