Accident Overview
On June 1, 2023, at about 1000 mountain daylight time, an experimental, amateur-built MTO Sport gyroplane, registration N207AG, was substantially damaged during a landing accident near Gardiner, Montana. The pilot, who was the sole occupant, received minor injuries. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
According to the pilot, he had performed two takeoffs and two landings prior to departing for a short local flight. Upon return, he made an approach to land on runway 10. After touchdown, while the gyroplane was traveling at about 10 mph forward speed, it suddenly yawed to the right despite the pilot applying full left rudder and nosewheel steering. The gyroplane then rolled to the left, and the rotors contacted the runway, substantially damaging the rotor mast. The gyroplane came to rest on its right side off the left side of the runway. All major components remained attached except for a segment of one rotor blade.
Postaccident Examination
Postaccident examination revealed that the left side of the metal mechanical stop for the nosewheel was bent downward, and the nosewheel was turned right beyond the mechanical stop limit. Three of the four control rods that provide rudder movement and nosewheel steering had fractured and separated from their respective rod end bearings. No preimpact mechanical malfunctions or anomalies were observed that would have precluded normal operation.
Further examination of the control rods showed that each control rod separated through the threaded end of one of the rod end bearings. The separations occurred through one of the top threads whose thread root was inline with the top of the mating nut. The macro shapes of the separations were cup-and-cone, consistent with overstress. The fracture surface of the longest control rod had intergranular features consistent with tensile overstress, possibly due to low toughness. The fracture surfaces on the other two control rods had features consistent with ductile tensile overstress.
Control System Description
The gyroplane was a two-seat model with flight controls installed for both seats. According to the manufacturer, the rear rudder pedals are connected to the rudder via steel cables and to the front pedals by linkages (control rods) via the nosewheel for steering. The design was built to BCAR Section T, “Light Gyroplanes” standards. The manufacturer stated that normal pilot inputs will not bend the nosewheel limit stop. A visual examination of the mechanical stop revealed the left-side stop was bent downward, which allowed the nosewheel to travel beyond its mechanical limit.
Weather and Runway Conditions
The closest weather reporting facility was Billings Logan International Airport (BIL), Billings, Montana. An automated weather report around the time of the accident recorded wind variable at 5 knots, 10 statute miles visibility, few clouds at 6,500 ft, few clouds at 10,000 ft, scattered clouds at 24,000 ft, temperature 24°C, dew point 11°C. The pilot reported the weather as fair and calm. According to a Gardiner Airport website, the runway conditions were described as “asphalt/aggregate friction seal coat, in poor condition. LARGE CRACKS AND VEGETATION GROWTH THROUGHOUT RUNWAY SURFACE.”