What was found
AIRCRAFT WAS CLEARED A VISUAL APPROACH. PILOT CALLED FOR GEAR DOWN AND BEFORE LANDING CHECKLIST, NOTICED THAT THE LEFT MAIN GEAR DOWN AND LOCKED LIGHT WAS NOT ILLUMINATED. PERFORMED A GO AROUND. AT A SAFE ALTITUDE, CYCLED THE GEAR. BOTH MAIN GEAR DOWN AN LOCKED LIGHTS DID NOT ILLUMINATE. TESTED THE LIGHTS WITH THE ROTARY TEST SWITCH. THEY COULD NOT GET THE TWO MAIN DOWN AND LOCKED LIGHTS TO ILLUMINATE. THE APPROPRIATE CHECKLIST WAS COMPLETED. USED THE BLOW DOWN GEAR SYSTEM. ONCE THAT WAS COMPLETE, A LOW APPROACH TO USE THE TOWER TO CONFIRM THE GEAR WAS DOWN. LANDING WAS MADE SAFELY AND TAXIED TO THE FBO.