ST. PAUL, MN, USA
N463US
BOEING 727-51
SHORTLY AFTER TAKEOF, THE AIRCRAFT EXPERIENCED AN UNCONTAINED 7TH TO 8TH STAGE REMOVABLE SLEEVE COMPRESSOR SPACER FAILURE IN THE NUMBER 3 ENGINE. PIECES OF THE SPACER PASSED THROUGH THE NUMBER 2 ENGINES DUCT CAUSING COMPRESSOR STALLS IN THAT ENGINE. THE AIRCRAFT LANDED SUCESSFULLY 9 MINUTES AFTER TAKEOFF USING THE SINGLE GOOD ENGINE. METALLURGICAL ANALYSIS OF THE RECOVERED SPACER PIECES REVEALED THAT CADMIUM EMBRITTLEMENT HAD OCCURRED AROUND AT LEAST ONE TIEROD SLEEVE HOLE ON THE SPACER. THIS EMBRITTLEMENT OCCURRED BECAUSE THE SPACER WAS INCOMPLETELY PLATED WITH NICKLE DURING A SPACER MODIFICATION THAT TOOK PLACE IN 1975. THE INCOMPLETE NICKLE PLATING ALLOWED A SUBSEQUENT CADIUM LAYER TO COME IN CONTACT WITH THE STEEL SPACER, CAUSING THE EMBRITTLEMENT.
Source: NTSB Aviation Accident Database
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