Narrative:

I was cleared by ZBW for the visual approach to runway 18 at bml. As I placed the landing gear handle in the down position, I observed an abnormal indication on the landing gear annunciator lights. The green lights, indicating that the wheels were down and locked, illuminated normally for the nosewheel and right main wheel, but the left main light remained unlit and the red 'in-transit' light was illuminated. I leveled off at about 7500 ft MSL in good VFR conditions and informed center that I had a gear problem and that I wished to orbit bml while attempting to troubleshoot. Center acknowledged my call, offered any assistance I might require, and instructed me to advise my intentions when able. I attempted several techniques to correct the abnormal indication. Based on my knowledge of the excellent beechcraft landing gear system, I knew also that the most likely scenario was an electrical problem of some sort and that the gear was probably mechanically down and locked. Still, being several hundred mi from home base, circling a non twred airport, knowing passenger were waiting on the ground expecting me to turn around and fly them to new york when I arrived, and having another 3 1/2 hours of fuel on board, I opted not to land at bml. Instead, I notified center of my intention to return to the new york area and requested a new clearance. I was cleared, for the time being, to climb to 8300 ft MSL (for terrain clearance over the white mountains) and proceed direct to teb. After a couple mins, I was past the high terrain and cleared to maintain 8000 ft MSL. I selected pou for several reasons: I am very familiar with the airport, which has a control tower and crash fire rescue equipment facilities, the WX at pou -- as elsewhere throughout the northeast -- was clear, pou is within reasonable distance of my home in new york city, I needed to fly at least another 1 hour to burn off the fuel remaining in the left tank, and a friendly airframe and pwrplant mechanic with specific knowledge of bonanza XXXX runs a shop located at pou. As I flew over central new hampshire, center advised that a military F16 was maneuvering about 120 mi west of my position and could be vectored for an intercept to visually examine the bonanza's landing gear. The fighter pilot reported no abnormal appearance to the bonanza's landing gear operation, which reassuringly supported the conclusion that the problem was electrical and not mechanical. After 6 or 7 mins, the F16 broke off to the west, and I continued on course to pou. As with the fighter escort, all visual indications were normal. After my second pass, tower advised of the mechanic's suggestion that I cycle the landing gear up and then perform a manual gear extension prior to any attempt to land, so I climbed to 3000 ft MSL and performed the manual gear extension, leaving the landing gear down. Fortunately, the incident ended uneventfully as I touched down first on the right main wheel, then on the nosewheel, and finally on the left main wheel. On rollout, the left main gear down annunciator light illuminated and the in-transit light went out, leaving me with a normal '3-green' indication. As I completed the requisite paperwork with the crash fire rescue equipment chief and county sheriff, the mechanics quickly confirmed that a switch in the left main gear -- original from the airplane's manufacture in 1986 -- had worn and partially failed, causing the erroneous indication. Over the next few days, the part was replaced, the aircraft log was updated, and the airplane was returned to service.

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Original NASA ASRS Text

Title: A BEECH A36 IN CRUISE AT 8300 FT DIVERTED DUE TO L MAIN GEAR UNSAFE INDICATION CAUSED BY A FAILED L MAIN GEAR DOWN AND LOCK SWITCH.

Narrative: I WAS CLRED BY ZBW FOR THE VISUAL APCH TO RWY 18 AT BML. AS I PLACED THE LNDG GEAR HANDLE IN THE DOWN POS, I OBSERVED AN ABNORMAL INDICATION ON THE LNDG GEAR ANNUNCIATOR LIGHTS. THE GREEN LIGHTS, INDICATING THAT THE WHEELS WERE DOWN AND LOCKED, ILLUMINATED NORMALLY FOR THE NOSEWHEEL AND R MAIN WHEEL, BUT THE L MAIN LIGHT REMAINED UNLIT AND THE RED 'IN-TRANSIT' LIGHT WAS ILLUMINATED. I LEVELED OFF AT ABOUT 7500 FT MSL IN GOOD VFR CONDITIONS AND INFORMED CTR THAT I HAD A GEAR PROB AND THAT I WISHED TO ORBIT BML WHILE ATTEMPTING TO TROUBLESHOOT. CTR ACKNOWLEDGED MY CALL, OFFERED ANY ASSISTANCE I MIGHT REQUIRE, AND INSTRUCTED ME TO ADVISE MY INTENTIONS WHEN ABLE. I ATTEMPTED SEVERAL TECHNIQUES TO CORRECT THE ABNORMAL INDICATION. BASED ON MY KNOWLEDGE OF THE EXCELLENT BEECHCRAFT LNDG GEAR SYS, I KNEW ALSO THAT THE MOST LIKELY SCENARIO WAS AN ELECTRICAL PROB OF SOME SORT AND THAT THE GEAR WAS PROBABLY MECHANICALLY DOWN AND LOCKED. STILL, BEING SEVERAL HUNDRED MI FROM HOME BASE, CIRCLING A NON TWRED ARPT, KNOWING PAX WERE WAITING ON THE GND EXPECTING ME TO TURN AROUND AND FLY THEM TO NEW YORK WHEN I ARRIVED, AND HAVING ANOTHER 3 1/2 HRS OF FUEL ON BOARD, I OPTED NOT TO LAND AT BML. INSTEAD, I NOTIFIED CTR OF MY INTENTION TO RETURN TO THE NEW YORK AREA AND REQUESTED A NEW CLRNC. I WAS CLRED, FOR THE TIME BEING, TO CLB TO 8300 FT MSL (FOR TERRAIN CLRNC OVER THE WHITE MOUNTAINS) AND PROCEED DIRECT TO TEB. AFTER A COUPLE MINS, I WAS PAST THE HIGH TERRAIN AND CLRED TO MAINTAIN 8000 FT MSL. I SELECTED POU FOR SEVERAL REASONS: I AM VERY FAMILIAR WITH THE ARPT, WHICH HAS A CTL TWR AND CFR FACILITIES, THE WX AT POU -- AS ELSEWHERE THROUGHOUT THE NE -- WAS CLR, POU IS WITHIN REASONABLE DISTANCE OF MY HOME IN NEW YORK CITY, I NEEDED TO FLY AT LEAST ANOTHER 1 HR TO BURN OFF THE FUEL REMAINING IN THE L TANK, AND A FRIENDLY AIRFRAME AND PWRPLANT MECH WITH SPECIFIC KNOWLEDGE OF BONANZA XXXX RUNS A SHOP LOCATED AT POU. AS I FLEW OVER CENTRAL NEW HAMPSHIRE, CTR ADVISED THAT A MIL F16 WAS MANEUVERING ABOUT 120 MI W OF MY POS AND COULD BE VECTORED FOR AN INTERCEPT TO VISUALLY EXAMINE THE BONANZA'S LNDG GEAR. THE FIGHTER PLT RPTED NO ABNORMAL APPEARANCE TO THE BONANZA'S LNDG GEAR OP, WHICH REASSURINGLY SUPPORTED THE CONCLUSION THAT THE PROB WAS ELECTRICAL AND NOT MECHANICAL. AFTER 6 OR 7 MINS, THE F16 BROKE OFF TO THE W, AND I CONTINUED ON COURSE TO POU. AS WITH THE FIGHTER ESCORT, ALL VISUAL INDICATIONS WERE NORMAL. AFTER MY SECOND PASS, TWR ADVISED OF THE MECH'S SUGGESTION THAT I CYCLE THE LNDG GEAR UP AND THEN PERFORM A MANUAL GEAR EXTENSION PRIOR TO ANY ATTEMPT TO LAND, SO I CLBED TO 3000 FT MSL AND PERFORMED THE MANUAL GEAR EXTENSION, LEAVING THE LNDG GEAR DOWN. FORTUNATELY, THE INCIDENT ENDED UNEVENTFULLY AS I TOUCHED DOWN FIRST ON THE R MAIN WHEEL, THEN ON THE NOSEWHEEL, AND FINALLY ON THE L MAIN WHEEL. ON ROLLOUT, THE L MAIN GEAR DOWN ANNUNCIATOR LIGHT ILLUMINATED AND THE IN-TRANSIT LIGHT WENT OUT, LEAVING ME WITH A NORMAL '3-GREEN' INDICATION. AS I COMPLETED THE REQUISITE PAPERWORK WITH THE CFR CHIEF AND COUNTY SHERIFF, THE MECHS QUICKLY CONFIRMED THAT A SWITCH IN THE L MAIN GEAR -- ORIGINAL FROM THE AIRPLANE'S MANUFACTURE IN 1986 -- HAD WORN AND PARTIALLY FAILED, CAUSING THE ERRONEOUS INDICATION. OVER THE NEXT FEW DAYS, THE PART WAS REPLACED, THE ACFT LOG WAS UPDATED, AND THE AIRPLANE WAS RETURNED TO SVC.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.