Date: 201909
Local time of day: 1201-1800
Location: ZZZ.TRACON, US
Flight conditions: IMC
Weather elements / visibility: Cloudy
Aircraft: Small Aircraft; Low Wing; 2 Eng; Retractable Gear
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
ATC / advisory: TRACON ZZZ
Aircraft component: Landing Gear Indicating System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed in Emergency Condition
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I got this airplane in ZZZ. During the preflight all of the annunciator lights; including the three green gear lights worked. Once at cruise; I noticed a lot of post lights were out. As it was cloudy and getting darker; I started to change some of the post lights. I then pressed the press to test to make sure all of those lights were still working as they were on the ground. When I hit the press to test button; I noticed the right main landing gear green light was not illuminated. I thought to myself that this must be a bulb that burned out; and went into the QRH (Quick Reference Handbook) to find the 'bulb replacement' procedure. I followed the steps in QRH 5.6; and the bulb still did not come on. I consulted with a senior pilot on company frequency to get advice about if I should declare an emergency; because I knew I would need to blow the gear down. We agreed it was the smart and safe thing to do. I [notified ATC] with ZZZ Approach. I told them I needed a heading to let the passengers know what was going on. I let the passengers know what was happening; and also called SOC (System Operations Control). SOC asked if I could come to [base]; which I said I could. I told Approach that I would like to divert to [base] and [notify ATC]; and have emergency personnel standing by as a precaution. I then went to page 5.2 (as the QRH says to do) to go about blowing down the gear. While I was on base for XX in [base]; I went below 130 KTS and put the gear down. I did have 3 green lights; but continued to follow the procedure as outlined in QRH 5.2 to be safe and pre-cautionary. I then blew the gear down per QRH 5.2. I landed on XX in [base] without incident. Emergency personnel followed me off the runway and I stopped the aircraft. Airport Ops came and got my passengers off the aircraft. I then had MX (Maintenance) tow the aircraft as a precaution to the fleet and wrote up the aircraft. One passenger on the flight was a [other carrier] Captain and was pleased that I took pre-cautionary measures to ensure a safe and un-eventful landing. He told me through his years you always go by the book and complimented me on my professionalism and smooth landing. The passengers were brought to the gate and got on another aircraft with another pilot to head to ZZZ1. I explained the situation to the MX personnel; called the on-call duty manager and filled out necessary paperwork.




Synopsis: Pilot flying light twin encountered gear indication light anomaly.