What was found
DFW - FLT 3311 - DURING DESCENT, THE CREW REPORTED THE LANDING GEAR WOULD NOT EXTEND, CREW FOUND CB F7 POPPED. F7 WAS RESET AND LANDING GEAR THEN EXTENED NORMAL. MAINTENANCE COULD NOT DUPLICATE DISCREPANCY. AN OPERATIONAL CHECK AS COMPLIED WITH, NO DEFECTS NOTED. AIRCRAFT WAS THE RETURNED TO SERVICE. (M)