What was found
AFTER DEPARTING SJU, WHEN GEAR WAS SELECTED UP AFTER T/O, GEAR WOULD NOT LOCK IN THE UP POSITION AND THE AIRCRAFT LOST HYDRAULIC PRESSURE. DECLARED AN EMERGENCY, EXTENDED THE GEAR USING THE EMERGENCY GEAR PROCEDURES, RETURNED TO SJU AND LANDED WITHOUT INCIDENT. MX INSPECTED THE HYDRAULIC SYSTEM, MX NOTED THE NLG UP HYDRAULIC TUBE UNDER THE COCKPIT FLOORBOARD HAD A LOOSE B-NUT WHERE THE FITTING GOES THROUGH THE FUSELAGE FLOOR. REMOVED THE B-NUT AND INSPECTED THE FLARED FITTING, NO DISCREPANCIES WERE NOTED. TIGHTENED FITTING, AND CHECKED THE OTHER FITTINGS IN THAT AREA FOR SECURITY. CONDUCTED SEVERAL GEAR SWINGS AND NO FURTHER LEAKS WERE NOTED. LAST LETTER CHECK E WHICH INSPECTS THE UNDER FLOOR AREA OF THE COCKPIT WAS CONDUCTED 09/29/2011, 507.7 FLIGHT HOURS AGO.