What was found
NR 3 ENG FIRE IND IN FIRE SWITCH AND "B" LOOP AT 9.5 DURING CRUISE. "A" LOOP INOP. ENG SHUTDOWN AND BOTH FIRE BOTTLES DISCHARGED AND FIRELIGHT REMAINED ON. CONDITIONS BEFORE SHUTDOWN, OIL PRESSURE 47-PSI OIL TEMP 88. NO IGNITION OR ANTI-ICE. AFTER SHUTDOWN, OIL PRESSURE 17 WINDMILLING 45 MIN. 4 PSI PRESSURE FOR 6 MIN. DURING APPROACH AND LANDING, OIL TEMP 88. ENGINE STABLE THROUGHOUT. REMOVED AND REPLACED NR 3 (2EA) FIRE EXTINGUISHER BOTTLES IAW MM CH 26-21-03, SYS OPS CHECKS NORMAL. REMOVED AND REPLACED "A" AND "B" LWR AFT FIRE SENSOR ELEMENT IAW MM CH 26-11-02, SYS OPS CHECKS NORMAL. INSPECTED NR 3 ENG FOR ANY OTHER DEFECTS NO OTHER DEFECTS NOTED. ENG SHUT DOWN DUE TO FAULTS IND OF FIRE SENSOR ELEMENTS.