CARSON CITY, NV, USA
N38JK
John H. Korb Jr. KITFOX III
The pilot stated that the purpose of the flight was to conduct touch-and-go landings. On the fourth touch-and-go landing the airplane veered to the right and the pilot attempted an unsuccessful go-around. Examination of the aircraft revealed a broken shock cord on the right main landing gear. Examination of aircraft records revealed that the aircraft had recently completed an annual inspection and the airframe had accrued 125 hours, without replacement of the shock cords. The shock cord was inspected, and found to exhibit internal ultra violet aging due to the abraded outside fabric lacing. According to the manufacturer, the shock cords are designed to be the weakest link in the landing gear system, and will fail at some point. He further stated that the shock cords should be replaced at the annual inspection. As a result of the accident, it was found that no provisions were made in the annual inspection checklist for replacement of the shock cords during the annual inspection. In the manufacturer's newsletter, under Maintenance Items, there was a reminder to replace the shock cords annually. The pilot stated that he was not aware that the shock cords needed to be replaced on an annual basis, as this was not mentioned in the annual inspection checklist. The manufacturer has since amended the annual inspection checklist to require replacement of the shock cord on an annual basis.
On May 24, 1998, at 0930 hours Pacific daylight time a Korb Kitfox III, N38JK, an experimental airplane, veered to the right off runway 27 while practicing touch-and-go landings at the Carson City, Nevada, airport. The airplane, operated under 14 CFR Part 91, sustained substantial damage. The private pilot/owner/builder, and a pilot rated passenger were not injured. Visual meteorological conditions existed for the local personal flight and no flight plan was filed. The pilot reported that on the fourth touch-and-go landing, the airplane veered to the right and departed the runway. The pilot attempted a go-around, but he stated that the airspeed was too low. He reported that the shock cord on the right main landing gear broke, "making it impossible to control the airplane." According to a Federal Aviation Administration (FAA) inspector, the airplane had recently gone through an annual inspection 2 months prior to the accident with no discrepancies noted. Approximately 125 hours had accrued on the airframe since the annual inspection, with no replacement of the shock cords. The kit manufacturer stated that they recommend replacement of the shock cord at the time of the annual inspection. The Product Development Manager from the airplane kit manufacturer inspected the shock cord. He stated that the shock cord is designed to be the weak link in the landing gear system and will fail at some point. The manager stated that the ends showed signs of ultra violet aging on the internal rubber that may have been caused by missing outer fabric lacing, or from it being worn through at the break point. He further stated that there was damage on the outer fabric lacing which may have been due to abrasion or from over stress. The report stated that signs of UV and abrasion to the bungee "point toward the shock cord rubbing on something that may or may not have played a part on the failure." The manager further stated that the airplane will normally veer away from the broken cord; however, it is possible with certain variables in place for the airplane to travel the same direction as the broken shock cord due to added drag on that side. Review of the manufacturer's maintenance and inspection criteria revealed that there were no provisions made in the annual inspection checklist for replacement of the shock cords during the annual inspection due to natural aging of the shock cord. In the manufacturer's newsletter, under Maintenance Items, there is a reminder to replace the shock cords annually. The pilot stated that he was not aware that the shock cords needed to be replaced on an annual basis. The manufacturer has since amended the annual inspection checklist to "replace bungee (recommended each year due to natural aging of bungee)."
The failure of the right landing gear shock cord because of ultraviolet deterioration in an area of abraded outer fabric, that resulted in a loss of directional control on landing and subsequent ground collision. Factors were the owner/builder's failure to replace the worn shock cord, and the kit manufacturer's failure to include its replacement in the annual inspection checklist.
Source: NTSB Aviation Accident Database
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