Accident Overview
On August 27, 2017, at approximately 1530 eastern daylight time, a Cessna 305A, registration N1834, sustained substantial damage when it nosed over and came to rest inverted on the turf runway at Wurtsboro-Sullivan County Airport (N82), Wurtsboro, New York. The commercial pilot, who was the sole occupant, reported minor injuries. The airplane was operated under Title 14 Code of Federal Regulations Part 91 as a glider tow flight. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight.
According to the pilot, he had completed five glider tow flights before the accident. After landing on the turf runway, during the landing roll, he noticed a severe vibration. The airplane then stopped, nosed over, and came to rest inverted. During the accident sequence, the wings and rudder were substantially damaged, and the left main landing gear wheel separated from its axle.
Aircraft and Operator Information
The Cessna 305A was manufactured in 1964 and was equipped with a Continental Motors Inc. O-470 series engine, producing 213 horsepower. According to Federal Aviation Administration records, the most recent annual inspection was completed on September 3, 2016, at a total time of 4,677.8 hours, at which time the aircraft was found to be in airworthy condition. The airplane was registered to and operated by a corporation.
Investigation Findings
The National Transportation Safety Board Materials Laboratory examined the left main landing gear wheel axle. The axle was fractured near the end that would have been attached to the landing gear strut. Examination under a stereo microscope revealed fracture features consistent with a fatigue fracture. Two opposing fatigue regions were present on the fracture surface, separated by an overstress region. The first fatigue region had a shiny appearance, consistent with recontact of the fracture surfaces. The second fatigue region exhibited a more matte appearance and covered a larger area than the first region. Additionally, the tread of the rubber tire displayed a wear pattern that was not centered but had shifted toward the shoulder.
Regulatory Context
The inspection requirements under Part 43 Appendix D – Scope and Detail of Items (as Applicable to Particular Aircraft) To Be Included in Annual and 100-Hour inspections specify that for the landing gear group, each person performing an inspection shall inspect all units for poor condition and insecurity of attachment; linkages, trusses, and members for undue or excessive wear fatigue and distortion; wheels for cracks, defects, and condition of bearings; and tires for wear and cuts.