What was found
FLIGHT 1870 EN-ROUTE, AFTER ROTATION, THE FLIGHT CREW HEARD A UN-NORMAL CLUNK. THE GEAR HANDLE WAS PLACED UP. THE GEAR INDICATORS SHOWED GREEN SOLID ALL 3 & FLASHING RED ON NOSE & RT MAIN GEAR. ALSO, A GEAR UNSAFE ECAM MSG CAME ON. THE CREW TRIED CYCLING THE GEAR, BUT WAS UNSUCCESSFUL. THE FLIGHT DECLARED AN EMER, RETURNED & DID A FLYBY OF THE TOWER TO CONFIRM THAT THE GEAR WAS DOWN. THE FLIGHT LANDED WITHOUT FURTHER INCIDENT. REPLACED NLG EXTENSION PROXIMITY SENSOR 25GA. PERFORMED A GEAR SWING & FUNCTIONAL CHECKS WITH NO ABNORMAL INDICATIONS OR NOISE NOTED.