What was found
(CAN) AFTER HOT SECTION INSPECTION THE ENGINE WAS RUNNING HOT. WHEN THE ENGINE WAS SPLIT THE TECHNICIAN NOTICED THE COMPRESSOR TURBINE SHROUD SEGMENT RETAINING RING HAD FALLEN BEHIND THE VANE. THE SEGMENTS MOVED AND CAUSED COMPRESSOR TURBINE BLADE TIP RUBS. THIS PROBLEM HAS BEEN DOCUMENTED ON AT LEAST 5 OTHER ENGINES THAT THE AUTHOR IS AWARE OF. MFG HAS ISSUED P/N 3110741-02 RETAINING RING ON SB 13121 (60A, 61, 62, 65 SERIES) AND SB 3248 (41/42, 45 SERIES) TO PREVENT THE COLLAPSE OF THE RETAINING RING. THE LATTER SB HAS NOT BEEN ISSUED ON SMALLER ENGINE MODELS SUCH AS THE 114A ENGINE MODEL TO ALLOW THE MORE ROBUST RETAINING RING TO BE USED.