What was found
(CAN) AFTER SLIGHT REDUCTION IN PWR SETTING PILOT HEARD A WHOOSH SOUND FOLLOWED BY N1 LOW RPM AUDIO WARNING HORN. CO-PILOT IDENTIFIED NR1 ENG IN A ROLLBACK CONDITION WITH A DECREASING N1 SPEED AND AN INCREASING T5 TEMP. AFTER VERIFICATION, EXECUTED A SHUTDOWN OF NR 1 ENG. FOLLOWED BY ENGAGEMENT OF ENG STARTER TO MOTOR ENG IN ORDER TO COOL DOWN T5 OVER-TEMP CONDITION OF 805 DEGREES C. WITH ENG TEMP IN AN ACCEPTABLE RANGE, MOTORING PROCEDURES DISCONTINUED, AC RETURNED, MADE A SINGLE ENG LANDING. A REPLACEMENT ENG, FREE TURBINE, FCU AND P&D VALVE WERE INSTALLED. ENG WAS GROUND TESTED AND AC WAS RETURNED TO SERVICE. AS A RESULT OF HAVING 2 ENGINE ROLL BACKS, FUEL SAMPLES WERE TAKEN FROM AC AND SENT FOR ANALYSIS.