What was found
(CAN) DURING APPROACH ALL 3 GEAR WOULD NOT EXTEND. PILOTS PERFORMED ABNORMAL CHECKLIST, THEN PERFORMED THE EMERGENCY GEAR EXTENSION, WHICH WORKED PROPERLY AND INDICATED ALL 3 GEAR WERE DOWN. THE CONTROL TOWER WAS INFORMED AND EMERGENCY VEHICLES DISPATCHED AS A PRECAUTION. THE PILOTS PROCEEDED TO MAKE AN UNEVENTFUL LANDING AND TAXIED TO THE FBO. MAINTENANCE PERSONNEL TROUBLESHOOTING, FOUND THE LANDING GEAR SELECTOR VALVE TO BE AT FAULT. THE VALVE WAS CHANGED AND THE LANDING GEAR SYSTEM FUCTION CHECKED SERVICEABLE. (TC# 20090918002)