On February 18, 1995, a Short Brothers SD3-60 (registration N376MQ) operated by Executive Airlines Inc. was involved in an aviation accident near St. Thomas. No fatalities were reported. Investigators recorded the probable cause as: The manufacturer's failure to apply sealant on the internal surface of the cylinder nut in the radius area between the threads and the flange before assembly, which led to stress corrosion cracking of the cylinder nut and subsequent collapse of the right main… This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.
During landing rollout, the right main landing gear collapsed. Investigation revealed the manufacturer had omitted sealant on a cylinder nut, leading to stress corrosion cracking and failure.
Incident Overview
The right main landing gear collapsed during the landing rollout. The Federal Aviation Administration (FAA) conducted an initial examination of the airplane, which revealed that the right main landing gear shock absorber had failed.
Laboratory Examination
Further examination of the components by the National Transportation Safety Board (NTSB) laboratory identified the root cause of the failure. The manufacturer had not applied sealant on the internal surface of the cylinder nut in the radius area between the threads and the flange before the nut was assembled. This omission allowed the development of stress corrosion cracking in the cylinder nut.
Conclusion
The stress corrosion cracking of the cylinder nut led to its failure, resulting in the subsequent collapse of the right main landing gear.
Probable cause
The manufacturer's failure to apply sealant on the internal surface of the cylinder nut in the radius area between the threads and the flange before assembly, which led to stress corrosion cracking of the cylinder nut and subsequent collapse of the right main landing gear.
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