NTSB Identification: CHI97IA117.
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Scheduled 14 CFR UNITED AIRLINES
Incident occurred Monday, April 28, 1997 in CHICAGO, IL
Probable Cause Approval Date: 06/26/1998
Aircraft: Boeing 737-200, registration: N9063U
Injuries: 2 Minor,56 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.
The airplane experienced an uncontained failure of the 10th stage compressor disk in the right engine. The flight crew aborted the takeoff, and an emergency evacuation was conducted after an engine fire was reported to the flight crew. Metallurgical inspection of the disk revealed that it had received insufficient nickel plating when it was reworked at the operator's facility 38 flight hours and 33 cycles prior to the incident. This resulted in cadmium embrittlement of the steel. The investigation revealed the operator had no written procedures to outline the process parameters and rectifier set-ups to be used during the NiCad plating process. NiCad plating line personnel also did not have any means of checking the thickness of the nickel plating during the plating process.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: inadequate nickel plating was applied to the compressor disk during the rework process at the operator's overhaul facility, which resulted in a brittle fracture in the disk and an uncontained engine failure. A factor was the operator's lack of written procedures and guidance for personnel on the NiCad plating line, along with their failure to supply a method of measuring the thickness of nickel applied. Full narrative available
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