As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
COUPLING HAS EXCESSIVE FRETTING WEAR ON OD SURFACE. CONTINUED OPERATION MAY HAVE CAUSED FAILURE. SAME CONDITION NOTED ON OTHER COUPLINGS OF THE SAME PART NUMBER. THIS PART NUMBER IS CURRENTLY UNDER INVESTIGATION BY ROLLS-ROYCE (ALLISON ENGINE COMPANY)DUE TO FAILURES OF LIKE PARTS.