What was found
CLIMBING THRU 18,000 FT, EXPERIENCED A LT ENGINE FAILURE. DECLARED AN EMERGENCY & DIVERTED. HEAVY VIBRATION IN AIRFRAME, AILERONS, ELEVATOR & RUDDER. FELT IT WAS A CATASTROPHIC ENG FAILURE, PERFORMED ENG SHUTDOWN CHECKLIST. AN UNEVENTFUL LANDING ACCOMP. INSP REVEALED EXTENSIVE DAMAGE TO LPT. INVESTIGATION FOUND ENG FAILURE DUE TO SEPARATION OF ROTATING HPT2 INTERSTAGE SEAL, WHICH DISRUPTED COOLING, LEADING TO HEATING OF HPT2 DISK RIM. DISK GROWTH ADVANCED TO A SINGLE HPT2 BLADE NO LONGER SECURED, SEPARATION OF THE SINGLE HPT2 BLADE. SEPARATION CAUSED FAILURE TO ADJACENT & DOWNSTREAM FLOW PATH. ENGINE BEYOND ECONOMIC REPAIR & REPLACED. ONGOING ROOT CAUSE INVESTIGATION CONDUCTED MANUFACTURER.