What was found
IN FLIGHT, AFTER NORMAL GEAR RETRACTION , RED GEAR LIGHT ON AFTER UP LATCH CHECK. FOLLOWED ABNORMAL CHECKLIST. REMOVED AND REPLACED LEFT GEAR UP LATCH CYLINDER IAW MM, REMOVED AND REPLACED LEFT GEAR ACTUATING CYLINDER IAW MM. PERFORMED CHECK, NO LEAK, GOOD. PERFORMED GEAR EXTENSION AND RETRACTION IAW MM AND CHECKED INDICATION IAW MM. FOUND NORMAL OPERATION.