NTSB Identification: CHI85IA097.
The docket is stored on NTSB microfiche number 28018.
Scheduled 14 CFR NORTHWEST ORIENT AIRLINES
Incident occurred Saturday, January 26, 1985 in ST. PAUL, MN
Aircraft: BOEING 727-51, registration: N463US
Injuries: 61 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

MAINTENANCE,MODIFICATION..IMPROPER..OTHER MAINTENANCE PERSONNEL

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

IMPROPER USE OF PROCEDURE..OTHER MAINTENANCE PERSONNEL



Contributing Factors

COMPRESSOR ASSEMBLY..BRITTLE FRACTURE


Index for Jan1985 | Index of months