Helena, MT, USA
N959D
Stinson 108-2
The pilot reported that shortly after applying power for takeoff, the airplane started to track left of runway centerline. During his attempts to correct the situation, the airplane's right main wheel assembly and right landing gear strut collapsed. Post-accident examination of the wheel assembly and tire installed on the accident airplane revealed that the outboard wheel subassembly fractured in multiple locations along the bead seat ring. Multiple fractures were observed in the inboard wheel subassembly, and the brake disc had partially separated from the wheel. The Type Certificate Data Sheet for the airplane lists multiple approved wheel-brake assemblies for the aircraft. The wheel assembly found on the airplane is not listed as one of the approved installations, and the wheel assembly was not approved for use with tires larger than size 7.00-6. The accident airplane was equipped with 8.00-6 size tires. The airplane's last inspection, an annual inspection, was performed on March 7, 2002.
On April 20, 2002, about 1230 mountain daylight time, a tail-wheel equipped Stinson 108-2, N959D, experienced a right main gear collapse while on takeoff roll at the Helena Regional Airport, Helena, Montana. The commercial pilot and the two passengers aboard the airplane were not injured, however, the airplane sustained substantial damage. The Title 14, CFR Part 91personal flight was being operated in visual meteorological conditions, and no flight plan was filed. The pilot reported that he was departing from runway 34, and that shortly after applying power for takeoff, the airplane started to track left of runway centerline. During his attempts to correct the situation, the airplanes right main wheel assembly and right landing gear strut collapsed, resulting in substantial damage to the firewall and right aileron. Post-accident examination of the Cleveland wheel assembly (model 40-113X), and tire (McCreary size 8.00-6), installed on the accident airplane, revealed that the outboard wheel subassembly fractured in multiple locations along the bead seat ring. Multiple fractures were observed in the inboard wheel subassembly, and the brake disc had partially separated from the wheel. The Type Certificate Data Sheet (TCDS), number A-767, for the Univair (Stinson) 108-2, lists multiple approved wheel-brake assemblies for the airplane. The Cleveland 40-113X wheel assembly is not listed as one of the approved installations. A representative from Parker Hannifin Corporation, Aircraft Wheel and Brake Division (Cleveland), also reported that the accident wheel assembly was approved for use with 6.00-6 and 7.00-6 sized tires, but not with 8.00-6 sized tires. Reviews of the maintenance records for the accident airplane indicate that the wheel assembly was installed on August 1, 1991. The records also indicate that the airplane's last inspection, an annual inspection, was performed on March 7, 2002.
Fracture of the left main wheel assembly during the takeoff roll. Factors include the use of a wheel assembly not approved for the accident airplane, and the use of an oversized tire.
Source: NTSB Aviation Accident Database
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