What was found
PDIS: HAD UNSAFE GEAR INDICATION ON ALL 4 GEAR ON BOTH PRIMARY AND SECONDARY INDICATORS. EXECUTED MISSED APPROACH AND COMPLIED W/QRH. GEAR RECYCLED ON OUTSIDE DOWNWIND IAW/QRH AND WE RECEIVED 4 DOWN AND LOCKED INDICATIONS ON PRIMARY AND SECONDARY INDICATORS. LANDED UNEVENTFULLY. JACKUP A/C. REPLACED LANDING GEAR SELECTOR VALVE AND HANDLE POSITION SWITCH H S1-431. PERFORMED LANDING GEAR EXTENSION/RETRACTION TEST IAW MM. RETURNED AIRCRAFT TO SERVICE.