A CE-560 flight crew noticed left main gear green light did not illuminate after gear extension. They determined the gear was probably down indicating a burned out bulb; but they elected to follow procedure and use the nitrogen bottle to ensure gear down. Landing was normal.

Narrative

The flight was from PBI to our destination. It was completely normal until I called for gear extension for the landing. We immediately noticed that the left main gear green (down/locked) light was not illuminated. I continued to fly the airplane while the Captain attempted to contact the company. I remained in level flight at the pattern altitude; notified Tower of our situation; declared an emergency and requested that the emergency equipment and crews be alerted. The Captain tried to contact the company via flight phone and cell phone; all without success. While he was doing so; I reduced the airspeed to less than 150 KTS and retarded the thrust levers to idle. The gear warning horn did not sound. I then extended the flaps to 35 degrees; and again the gear warning horn did not sound. This indicated that the gear was indeed down and locked; the warning light bulb was apparently burned out. Nevertheless; in accordance with our procedures; we executed the landing gear Will Not Extend checklist; using the emergency gear extension nitrogen bottle to blow the gear down. The gear light still did not illuminate. After completing the checklist we notified the Tower that we were ready to land. I made a straight-in visual approach and landing; which was uneventful. I stopped the airplane on the runway; and we shut down without moving it further. We arranged for our passengers to be picked up and for the FBO to tow the airplane to the ramp. We notified the company of the event as soon as we shut down the engines. After we arrived at the ramp we performed the required maintenance paperwork and postflight duties.