Accident Details
On September 27, 2022, at approximately 1458 mountain standard time, a Vashon R-7, registration N151VR, was substantially damaged during a takeoff attempt near Glendale, Arizona. The pilot, operating under 14 CFR Part 91 for personal flight, was not injured. According to the pilot, after aligning with the runway and applying power, the left main landing gear (MLG) collapsed when the aircraft reached 15–20 knots. The airplane then ground looped to the left, resulting in substantial damage to the left elevator and left wing.
Aircraft Information
The Vashon R-7 was equipped with a Dynon Skyview HDX avionics unit capable of recording flight parameters, including vertical acceleration, at 4 Hz and 16 Hz. Review of the recovered data showed a maximum recorded vertical acceleration of 1.7g that could be associated with a landing event. The left gear leg, manufactured from NP 130HF (a woven E-glass/epoxy prepreg laminate pressed and oven cured), fractured at the attachment point to the fuselage at the outboard bracket. The raw material was supplied as cured sheets 4 feet by 8 feet by 13/16 inch thick, waterjet cut into shape, with a vinyl wrap for UV protection. The lengthwise orientation of the gear leg was cut along the warp (0°) direction for maximum flexural strength, advertised as 85 ksi.
Landing Gear Examination
The National Transportation Safety Board Materials Laboratory examined the fractured left gear leg. The fracture surface intersected the center of the attachment bolt holes on the inboard side and extended through most of the thickness near the outboard edge, shifting downward toward the lower end of the outboard bracket faying surface. The surface near the inboard edge was relatively smooth in a translaminar plane with limited interlaminar fractures, while the middle and outboard areas were rougher with increased interlaminar fractures and variable fracture paths. A portion of the surface had a flattened appearance. Scanning electron microscopy revealed indications of progressive crack growth.
Manufacturer Actions
A batch of 16 airplanes (serial numbers 10140–10155) was identified as having potential material strength inadequacy in the landing gear. Four of these aircraft experienced main landing gear fractures, two of which followed hard landing events. One of those events was classified as an accident (NTSB accident ERA21LA158). Flexural destructive testing of specimens from the material batch remnants, failed gear, and gear from several serial airplanes yielded an average flexural strength of 70.2 ksi. Following these tests, Vashon Aircraft issued inspection guidance to owners of airplanes with landing gear from the affected batch, began destructive flexural testing of each new batch of material used for gear legs to verify strength standards, and initiated evaluation of a landing gear redesign.