Failure of a Screw in a Helicopter Fuel-Control Unit: Was It the Cause of a Fatal Crash?

摘要

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.