What was found
(CAN) AFTER THE CREW SELECTED LANDING GEAR DOWN, THE NLG DID NOT EXTEND NORMALLY. THE CREW DECLARED AN EMERGENCY, COMPLETED AN ALTERNATE EXTENSION AND LANDED WITHOUT FURTHER INCIDENT. NLG DOOR SOLENOID SEQUENCE VALVE AND NLG MECHANICAL SEQUENCE VALVE HAVE BEEN REPLACED. AFTER ADDITIONAL CHECKING/TESTING, NLG MECHANICAL SEQUENCE VALVE HAS BEEN CONFIRMED AS FAULTY. IT HAD INTERNAL LEAKAGE UP TO 500 PSI ON PORT C2 AND DN. AFTER REPLACEMENT ACFT FLOWN 4 FLIGHTS WITHOUT PROBLEM.