What was found
(CAN) ON FINAL APPROACH, FLT 650 AT APPROX 1830 HRS, FOLLOWING GEAR DOWN SELECTION, RT MLG UNSAFE INDICATION. GEAR CYCLED 2 TIMES, RT MLG STILL UNSAFE. ALTERNATE EXTENSION CARRIED OUT WITH SAME INDICATION. ALTERNATE DOWNLOCK INDICATION SHOWED THREE GREEN AFTER ALL GEAR DOWN SELECTIONS. AT APPOX. 17:15 HRS CET AN EMERGENCY LANDING WAS DECLARED AND THE AIRCRAFT LANDED WITHOUT INCIDENT.NOTE: TROUBLESHOOTING BY TECHNICIANS FOUND PRIMARY DOWNLOCK SENSOR OUT OF RIG. TOO FAR INDICATED ON PSEU. SENSOR RE-RIGGER AND PSEU CHECKED SERVICEABLE. CHECK / POSITIONING FLIGHT CARRIED OUT. NO FURTHER INCIDENTS.