Date: 201407
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737-300
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ; Tower ZZZ
Aircraft component: Instrument and Control Panels
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Distraction; Training / Qualification; Troubleshooting; Workload
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action; Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Ambiguous

Narrative: Prior to descent; the First Officer replaced a routine light bulb on the forward instrument panel. When he replaced the socket; multiple indicators failed to test when the Master Light Test/Bright/Dim switch was placed to TEST. On final; the First Officer called for the gear and the entire gear indication panel was dead (black). I sent the First Officer around and worked airspace over the bay to analyze the problem. I kept the First Officer flying and gave him the ATC radio. I established a conference call with Dispatch and Maintenance through radio patch. Maintenance had us check the two Start Valve Open light circuit breakers as this was the bulb that he had attempted to replace. Both the First Officer and I searched for open circuit breakers multiple times and couldn't find an open breaker. Maintenance had no other recommendations so I terminated the call. We looked through the Landing Gear section in the QRH and none of the checklists dealt with a 'dead' panel. We reviewed the Alternate Gear Extension Checklist; but we were extremely confident that with these events; an operable gear handle and good hydraulics that this was simply an indication problem. I coordinated with the flight attendants to leave the cockpit and verified that all landing gears were locked down. With fuel getting low; safe gear and good hydraulics; we decided to land. We flew a visual approach; landed uneventfully; and taxied to the gate.Sometimes in aviation; things happen. I don't think anything could have prevented it nor would I recommend any policy change. I do think Maintenance could have had us check the circuit breakers that controlled power to those blank indicators but didn't. I also think that pieces of checklists could be used to develop a separate checklist for a blank indicator panel; as all others deal with conflicting indications or stuck handle. The Bright/Dim power source; circuit breaker location; and visual confirmation procedures where all in the Alternate Gear Ext Checklist; but my initial tendency was that checklist didn't apply because we could operate the physical gear normally. So; if I dismissed that checklist at that point; I would've missed vital information that was essential to a safe landing. Also; the sighting windows could have been a bit cleaner. It took some time to figure out the angles and to clearly see the indications.




Synopsis: A B737 First Officer replaced a light bulb on the forward instrument panel and subsequently many lights failed to test. During approach the landing gear indicating system did not function so the crew went around to troubleshoot; then landed uneventfully without the indications.