What was found
AFTER TAKEOFF FROM LPLA, CREW EXPERIENCED LOSS OF HYDRAULIC FLUID. WHILE RUNNING CHECKLIST GOT A DOOR UNSAFE LIGHT ON THEN GEAR UNSAFE LIGHT. GEAR UPLATCH CHECK AFTER TAKEOFF WAS GOOD. FLUID LOST TO ALMOST TOP OF STANDPIPE. CREW RETURNED AIRCRAFT TO LPLA AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND HYDRAULIC LINE FITTING ON THE OUTLET SIDE OF THE NR 3 ENGINE HYDRAULIC PUMP LOOSE. TIGHTENED FITTING AS REQUIRED AND LEAKED CHECKED. MAINTENANCE PERFORMED INSPECTION OF THE MAIN AND NOSE GEAR DOORS WITH NO DEFECTS NOTED. PERFORMED OPERATIONAL AND LEAK CHECK AND ALL WAS NORMAL PER ALL APPLICABLE MANUALS. AIRCRAFT WAS RETURNED TO SERVICE.