Investigators in the U.K. determined the cause of a left-axle failure, which resulted in the wheel separating from a Ryanair Boeing 737 during taxiing before takeoff. Air Accidents Investigation Branch (AAIB) found that the axle journal sustained a re-tempering burn during post-chrome-plate grinding during overhauling. The heat-induced cracking in the base metal likely grew due to hydrogen embrittlement during cadmium plating.
Grind Retempering Caused 737 Axle Failure
November 19, 2018