WILDWOOD, NJ, USA
N10989
Bellanca 7GCBC
During the landing roll, the airplane's left main landing gear started to wobble and ultimately separated from the fuselage. The failed landing gear section was held in place with a through bolt near the center of the fuselage, and a u-bolt where the landing gear exited the fuselage. Examination of the failed bolts revealed corrosion pitting and the bolts had failed by overload. According to the airplane owner, the bolts had been in place for 20 years and had accumulated 580 hours. The manufacturer recommended replacement of the bolts when they had accumulated 500 hours, but did not list a calendar time for replacement. Additionally, there was no regulatory requirement for the owner to follow the manufacturer's recommendations.
On July 6, 2000, about 1440 Eastern Daylight Time, a Bellanca 7GCBC, N10989, was substantially damaged while landing at Cape May County Airport, Wildwood, New Jersey. The certificated airline transport pilot was not injured. Visual meteorological conditions prevailed for the personal flight, which originated from Eagle Creek Airport, Milton, Delaware. No flight plan had been filed for the flight that was conducted under 14 CFR Part 91. The pilot reported that the airplane touched down in a tail low attitude on Runway 01. After touchdown, the left main landing gear started to wobble. He raised the tail further, and the wobbling continued, after which, the left main landing gear separated from the airplane. The airplane remained on the runway and settled on its left wing, which fractured the wing spar. The separated left main landing gear came rest adjacent to the airplane. The main landing gear consisted of two spring steel pieces. Each piece was secured to the fuselage at two places, which included a through bolt inboard, and a u-bolt where the landing gear exited the fuselage. Both the u-bolt and inboard bolt had fractured on the left main landing gear. The fractured bolts were forwarded to the Safety Board Materials Laboratory for examination. According to the factual report: "The left gear u-bolt was fractured through the 90-degree bend that forms the forward leg of the bolt...The aft leg of the u-bolt was bent slightly rearward. Initial examination found that the fracture surfaces were obscured by red-to-black corrosion deposits...Optical examination of the cleaned fracture faces found features typical of an overstress separation. No indications of preexisting cracking, such as fatigue, were found." "The inboard straight bolt from the left gear was also fractured through the shank...Optical examination of the fracture found overstress features with no indications of progressive cracking. The bolt showed significant tensile yielding and necking (radial yielding), consistent with a predominately tensile loading. However, a small amount of bending deformation was also present." "Close examination of the outer diameter found that the surface of the bolt at the fracture location was pitted and corroded. The extent of pitting or diameter reduction could not be accurately established due to yielding. However, deep corrosion pits were visible around the entire diameter of the bolt. Other areas of heavy corrosion were also apparent near the bolt threads." "Corrosion was also visible on the diameter of the right gear inboard bolt, at the location corresponding to the fracture on the left gear bolt...The corrosion did not appear to be as severe as on the left bolt, but it had reduced the diameter by approximately 0.007 inches, from 0.435 to 0.428 inch." The hardness of the left and right bolts was found to be 36.4 HRC, and 36.5 HRC, respectively. The specified hardness was 34 to 40 HRC. According to the owner, at the time of accident, the bolts had accumulated 580 hours, and been in place for 20 years. A service bulletin from the manufacturer recommended the replacement of the bolts at 500 hours intervals, but did not specify a calendar time replacement. However, there was no requirement for the owner to follow the manufacturer's recommendations.
an improper flare by the pilot which induced an overload failure on the left side landing gear bolts. Factors were the corrosion on the bolts, and the failure of the operator to change the u-bolt in accordance with the manufacturer's recommendations.
Source: NTSB Aviation Accident Database
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