What was found
JOLT FELT IN FLIGHT AT 13,000 FEET, ENGINE INSTRUMENTS NORMAL, NO COCKPIT INDICATION OF MALFUNCTION. CARGO INSPECTED IN FLIGHT BY FIRST OFFICER. EMERGENCY DECLARED FOR LANDING. LANDING NORMAL, EXCEPT LEFT ENGINE THRUST REVERSER DID NOT GET BLUE LIGHT. INSPECTION IN BLOCKS SHOWED LEFT THRUST REVERSER DAMAGE. INSPECTED NR 1 ENGINE, FOUND NR 1 THRUST REVERSER UPPER DOOR DEPLOYED. BOTH UPPER AND LOWER DOORS DAMAGED. ALSO, DAMAGE TO THE NR 1 PYLON AT THE AFT LOWER ENGINE MOUNT AREA. REMOVED NR 1 ENGINE TO FACILITATE PYLON REPAIR, THEN REINSTALLED ENGINE AFTER REPAIR, REF M17 WORKPACK. REPLACED NR 1 THRUST REVERSER ASSEMBLY AND OPS CHECKED GOOD ON GROUND RUN.