Failure of a screw in a helicopter fuel-control unit: Was it the cause of a fatal crash?
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Investigations into a fatal helicopter crash centered around the failure of a cadmium-plated, non-conforming, steel screw in a fuel-control unit. The present study, which includes a critical evaluation of previous investigations, was undertaken with the aim of getting more definitive answers as to whether the screw failed in flight due to hydrogen-embrittlement or stress-corrosion cracking, or whether the screw failed due to liquid-metal embrittlement during a post-crash fire. Previous investigations had not resulted in any consensus regarding the mode of failure or whether the failure was responsible for the crash.
Keywordscadmium-plated steel screw energy-dispersive spectroscopy failure analysis hydrogen-embrittlement liquid-metal embrittlement stress-corrosion cracking
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