Accident Details
On November 9, 2011, at 1134 eastern standard time, an experimental amateur-built Greiner RV-8, registration N220RG, operated by an individual, was substantially damaged during landing at Boire Field Airport in Nashua, New Hampshire. The commercial pilot and a passenger were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under 14 Code of Federal Regulations Part 91. The flight had originated from the same airport earlier that day, at about 1030.
According to the pilot, the pleasure flight was uneventful. The wheel landing and landing roll were normal until approximately 1,000 feet down the runway, when the right main landing gear collapsed. The airplane then ground looped, resulting in structural damage to the right wing. The passenger also reported that the landing was uneventful until the ground loop occurred.
Examination Findings
Subsequent examination revealed that the right main gear spring attaching bolt had fractured. The landing gear had accrued approximately 80 hours of operation with an estimated 100 landings and was original to the manufacturer's kit. Components from the outboard and inboard landing gear spring brackets and fasteners were submitted to the NTSB Materials Laboratory for examination. All fractured components exhibited features consistent with overload failure. Additionally, X-ray fluorescence spectroscopy determined that both landing gear spring brackets were consistent with a 4120 steel alloy.
Subsequent Information
After the accident airplane was repaired, the pilot reported a possible explanation for the landing gear failure: the hardware installation. The pilot had received the airplane partially built, with the landing gear already assembled. The pilot noted that the landing gear bolts are difficult to access. Although he ensured the appropriate torque was applied to the hardware, he stated that one of the bolts may not have been seated properly. During the rebuild, he also identified fretting in the area, though no photographs were taken of the fretting. Since the accident, the pilot has been using a video borescope to conduct visual examinations of the area.