Freehold, NY, USA
N832LL
CZECH AIRCRAFT WORKS SPOL SRO SPORTCRUISER
The student pilot was practicing landings in a special light sport aircraft on an asphalt runway. After a soft touchdown, the nosegear collapsed and the airplane skidded approximately 30 feet before coming to rest on the runway. Examination of the wreckage revealed damage to the forward fuselage and firewall. The nosegear fork assembly separated from the nosegear strut on one end, and separated from the nosewheel on the other end. Further examination of the nosegear assembly revealed the fork of the assembly consisted of two aluminum fork leaves riveted together, which exhibited cracks. The inner fork leaf, which extended further than the outer leaf, had through holes for the wheel’s axle. The inner fork leaf was found to also have cracks on the side opposite the one that had separated. Microscopic examination revealed that the fractures on both pieces of the inner fork leaf were due to fatigue that initiated at multiple origins. Collectively, the fatigue cracks went through the thickness of the fork leaf. The large number of fatigue cracks was consistent with the nose gear fork assembly deteriorating for an extended period of time. The cracks were of a size that could be identified by visual examination. The nosegear strut exhibited slant fractures consistent with overstress. The airplane's most recent annual inspection was completed about 3 months, and 38 hours of operation, prior to the accident.
On June 18, 2010, about 1630 eastern daylight time, a special light sport aircraft (S-LSA) Czech Aircraft Works Spol Sro SportCruiser airplane, N832LL, operated by L & L Light Sport Aviation, was substantially damaged during landing at Freehold Airport (1I5), Freehold, New York. The student pilot was not injured. The solo instructional flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the local flight. The student pilot reported that he was practicing landings on runway 12, a 2,275-foot-long, 22-foot-wide, asphalt runway. He flared over the runway threshold and the main landing gear touched down on the center of the runway. As the nosegear touched down, the student pilot felt a sudden jolt and the propeller struck the runway. The airplane's nosegear had separated and the airplane skid approximately 30 feet, before coming to rest on the runway. Examination of the wreckage by a Federal Aviation Administration (FAA) inspector revealed damage to the forward fuselage and firewall. The inspector noted that the nosegear fork assembly had separated from the nosegear strut on one end, and separated from the nosewheel on the other end. The inspector did not observe any evidence of a hard landing, and noted cracks in the nosegear fork assembly. The nosegear fork assembly and strut were forwarded to the NTSB Materials Laboratory, Washington, DC, for further examination. The examination revealed the fork of the assembly consisted of two aluminum fork leaves riveted together. The inner fork leaf, which extended further than the outer leaf, had through holes for the wheel’s axle. A section of the inner fork leaf was received separated from the rest of the assembly. The rivets connecting the two fork leaves together had also separated. Visual examination revealed that the rest of the fork leaves, although they had not separated, all contained cracks and exhibited varying degrees of plastic deformation. The nose gear fork assembly was disassembled to examine the cracks on the fork leaves. The inner fork leaf was found to also have cracks on the side opposite the one that had separated. Laboratory fractures were created to open the cracks for microscopic examination. Microscopic examination revealed that the fractures on both pieces of the inner fork leaf were due to fatigue that initiated at multiple origins. Collectively, the fatigue cracks went through the thickness of the fork leaf. The large number of fatigue cracks was consistent with the nosegear fork assembly deteriorating for an extended period of time. The cracks were of a size that could be identified by visual examination. The nosegear strut exhibited slant fractures consistent with overstress. Two small areas on the fracture surface were flat, thumbnail like in appearance and oxidized, consistent with fatigue fractures. According to a representative at the FAA Small Aircraft Directorate, ASTM International (formerly known as the American Society for Testing and Materials) maintained the Design and Performance Standards for S-LSA. Due to nosegear failures on several different S-LSA models, ASTM was revising the standards. The last revision pertaining to the subject was during 2009, and the next revision was expected mid-year, 2011. The original manufacturer, Czech Aircraft Works was no longer in business and the product was currently supported by Czech Sport Aircraft; however, from January 2010, Czech Sport Aircraft no longer manufactured the SportCruiser as it was subsequently manufactured as the PiperSport, until January 2011. The airplane had accumulated 1,287 total hours of operation since new. The most recent annual inspection was completed on May 25, 2010 and the airplane had accrued 38 hours of operation since that inspection. During an interview with the FAA inspector, the airplane owner stated nothing abnormal was noted with the nosegear during the most recent annual inspection. The airplane owner estimated that the airplane experienced approximately 100 landings since the annual inspection. The airplane owner also reported that the airplane had experienced a nosegear shimmy about 1 year prior to the accident. Specifically, the nut that held the fork was loose. Once the nut was tightened, the shimmy ceased. According to a representative at Czech Sport Aircraft, the accident model underwent modification before becoming the PiperSport. The modification included a steel nosegear strut and with greater dimension; however, the fork leaves remained aluminum. Additionally, the newer model had a more effective anti-shimmy damper design. The representative further stated that additional guidance would be added to the maintenance manual, regarding a special inspection following the occurrence of a shimmy. The recorded wind, at an airport located 25 miles northeast of the accident site, at 1651, was variable at 3 knots. The student pilot reported the wind as calm during the landing.
The failure of the nosegear fork assembly due to fatigue. Contributing to the accident was an inadequate recent annual inspection.
Source: NTSB Aviation Accident Database
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