Date: 201811
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: Mixed
Weather elements / visibility: Cloudy; 3
Light: Daylight
Aircraft: Baron 55/Cochise
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class E ZME
ATC / advisory: Center ZME
Second aircraft: Small Transport
Reporter organization: Corporate
Reporter function: Single Pilot; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Commercial
Human factors: Workload; Distraction; Situational Awareness; Troubleshooting
Second reporter function: Approach
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Executed Go Around / Missed Approach
Contributing factors: Aircraft; Human Factors
Primary problem: Ambiguous

Narrative: While on the RNAV approach for runway X at the ZZZ airport; I leveled off at the intermediate altitude of 2100 between the fixes ZZZZZ and ZZZZZ1; and actuated the landing gear lever. I heard and felt the landing gear extending; and ran the before landing checklist; but did not see the only down and locked green light light up. Because of this; I was not sure the gear were in fact locked in the down position. Since the light is located directly behind the long; thick arm of the common elevator control; it was hard to tell if it was lit from my angle. I proceeded to cycle the gear once; and noticed that the up red light was working; but not the down green light. The passenger seated next to me also did not see the down green light. I then quickly removed the green 'down' light; and replaced it with the red 'up' light; but it did not seem to work in the 'down' socket either; as it did in its own socket. But while I was trying to determine the extent and cause of the malfunction; I did not notice that I had drifted several hundred feet below the charted altitude. Fortunately; by this point I had broken out of the clouds and was actually in VFR conditions; about 1000 feet above the ground; and about 7 miles from the airport. I determined that the ceiling and visibility would have then allowed me to continue to operate under VFR to the airport. But since I had not been cleared for the visual; and because there was an obstruction in the area at 935 feet; I began to climb back up to the charted altitude. By the final approach fix; I decided to do the missed approach to the hold over ZZZZZ2. I informed [ATC] of the situation; so as to get assistance with my problem. I ran the gear malfunction checklist; and was informed by a passing aircraft directed there by ATC that my all my landing gear appeared to be extended. Since nearby ZZZ has an ILS approach and the appropriate fire and rescue equipment; I elected to land there and asked for them to stand by. I got vectored for the ILS X approach; and landed as softly as possible. Having the flaps fully extended; and the power at idle did not result in a gear unsafe alarm. Since the gear behaved normally; and because I did not want to stop too abruptly; and because the fire trucks were blocking the first taxiway; I slowly continued to the second taxiway and exited the active runway and into the first ramp area available. I did this because I not want to go roll too far; just in case the gear were not secure; even though my passengers wanted me to continue all the way to the FBO. I cancelled my flight plan; and answered the questions of the lead Fire and Rescuer. The aircraft was then towed to a service shop on the field; where new bulbs were installed; and the landing gear was tested without any malfunctions detected. The aircraft was then released for continued normal operations by the mechanic. In retrospect; I should not have tried to diagnose the malfunction while on the approach; no matter how simple the action; because this caused me to be distracted and descend below a charted altitude; which could have been disastrous. It would have been more appropriate to discontinue the descent; proceed to go missed; and then try to fix the problem. Additionally; I should just have stopped on the runway as soon as possible; and not continue to roll or turn; as the gear might have been unsafe. Also; this is an old airplane; and I would like to suggest to the FAA that they not allow aircraft of a certain age to continue to operate normally; because of archaic and non-standard equipment; metal fatigue; worn parts; loose electrical connections; and lack of modern safety equipment; such as shoulder harnesses. I feel that too many old aircraft with components about to fail; along with pilots trying to operate unusual components hodge-podged together in these old 'Franken-planes;' in challenging conditions; will lead to accidents.


Second narrative: Aircraft X was on an instrument approach to ZZZ. He called missed and [notified us of an issue]. Pilot informed us that he wasn't sure if his landing gear was up or down. He said his landing gear light was off; indicating the gear was stuck in the up position. I instructed the pilot to execute the missed approach procedure and climb and maintain 050. Aircraft X told me he was in VFR conditions. Aircraft Y was also inbound to ZZZ and I asked the pilot if he would fly by and take a look. I cleared Aircraft Y from 060 to maintain 040. He told us that would put him in IMC. I climbed Aircraft X to 060 and Aircraft Y to 050. As Aircraft Y was descending he asked if 'we could do this at 060' because he was getting in the clouds at 055. I told him I could not have them at the same altitude and climbed Aircraft X to 070 and had Aircraft Y maintain 060. Aircraft Y had Aircraft X in sight but was too far below to see his landing gear. Aircraft Y climbed up to about 067 so that he could see that the landing gear was in fact down. I never asked or told the Aircraft Y pilot to climb but he had the aircraft in sight and he made very clear his intentions to follow the aircraft low and to the left. The pilots could hear each other on the frequency. If this happened again I would use visual separation and put the lower aircraft in a block altitude. I didn't realize how difficult it would be to see landing gear on a BE55 from 1000 feet below.


Synopsis: BE-55 pilot reported an altitude deviation while troubleshooting a gear unsafe indication. ATC reported attempting to help the BE-55 pilot.