What was found
GEAR EXTENSION AT DESTINATION RECEIVED GEAR DISAGREE. RAN QRH, CYCLED GEAR SEVERAL TIMES IAW QRH DISAGREEMENT PERSISTED. HAD TO EXTEND GEAR WITH MANUAL GEAR EXTENSION. LANDING SUCCESSFUL. AA&E MX C/W GVI OF ALL LANDING GEAR, NO OBVIOUS DEFECTS NOTED. C/W MX PROCEDURE & DEFERRED LANDING GEAR RERTACTION SYSTEM PER MEL 32-30-1. (FLIGHT 5219) PSEU AND FDR DATA INDICATED FAILURE OF THE NLG SELECTOR VALVE. REPLACED AND OPS CHECK OF SELECTOR VALVE. COMPLIED WITH CAT II RTS CARD 34-220-1021-SKY. RTS, OK FOR SERVICE