PLT OF A C210 LANDED WHEN THE GREEN LNDG GEAR INDICATING LIGHT DID NOT SHOW A DOWN AND LOCKED INDICATION. THE RPTR USED ALL APPROPRIATE CHKLISTS ACTIONS AND WITH KNOWLEDGEABLE MECHS IN THE TWR PRIOR TO LNDG. A SUCCESSFUL LNDG WAS MADE AND A POSTFLT GEAR INSPECTION DISCLOSED A FAULTY MAIN GEAR DOWN LOCK.

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I WAS ON APCH TO RWY 17 INTO ILM AT APPROX XX30 AM. AFTER CONTACTING THE TWR; I PROCEEDED TO PUT THE GEAR SWITCH DOWN. AT THE TIME I WAS ABOUT 4 MI FROM THE RWY WHEN I DID MY FIRST GUMPS CHK. THAT WAS WHEN I FIRST NOTICED THAT I DID NOT HAVE A GREEN LIGHT INDICATING THAT MY GEAR WAS DOWN AND LOCKED. I WENT AHEAD AND RECYCLED THE GEAR SWITCH AND STILL NO GREEN LIGHT. I PROCEEDED AT THAT TIME TO INITIATE A GAR AND NOTIFIED THE TWR OF THAT AND ALSO THAT I DID NOT HAVE A GREEN LIGHT IN THE COCKPIT. I ASKED THE TWR IF I COULD GO OUT E OF THE ARPT TO TROUBLESHOOT THE PROB. THEY SAID THAT WAS NO PROB AND TO KEEP THEM ADVISED IF I NEEDED ANYTHING. I PROCEEDED TO GET OUT THE CHKLIST AS WELL AS THE POH TO TROUBLESHOOT. I TRIED EVERYTHING THAT WAS WRITTEN AND STILL NO GREEN LIGHT. WHEN I PUT THE GEAR UP IT WOULD GO UP NORMALLY AND THE AMBER GEAR UP LIGHT WOULD ILLUMINATE AS NORMAL. HOWEVER WHEN I PUT THE GEAR SWITCH DOWN THE GEAR SOUNDED LIKE IT CAME DOWN NORMALLY BUT I NEVER GOT A GREEN LIGHT; THE HYD PUMP CONTINUED TO RUN UNTIL THE HYD PUMP CIRCUIT BREAKER POPPED. I KEPT THE TWR INFORMED OF MY SIT AND WHAT I WAS DOING TO TROUBLESHOOT THE PROB. THE TWR GOT 2 MECHS (WHO DO ALL THE MAINT ON THIS PARTICULAR PLANE) UP INTO THE TWR TO HELP. I PROCEEDED TO DO SEVERAL PASSES BY THE TWR SO THEY COULD OBSERVE MY GEAR. THEY INFORMED ME AFTER EACH PASS THAT ALL 3 WHEELS 'APPEARED' TO BE DOWN AND LOCKED; HOWEVER; THE FRONT GEAR CLAMSHELL DOORS REMAINED OPEN (THESE ARE SUPPOSED TO CLOSE UPON PROPER GEAR EXTENSION). MY CONCERN AT THAT TIME WAS THAT THE NOSE GEAR WAS NOT DOWN AND LOCKED BECAUSE I COULD VISUALLY CHK FOR THE L AND R MAINS FROM THE COCKPIT AND THEY 'APPEARED' TO BE DOWN AND LOCKED. AFTER APPROX 1 HR AND 15 MINS OF TROUBLESHOOTING AND 4 OR 5 TWR PASSES I FELT THAT I HAD RECEIVED ALL THE ADVICE I COULD GET UNDER THE CIRCUMSTANCES AND STILL NO GREEN LIGHT. THE MECHS SEEMED TO THINK THAT IT MAY JUST BE A BROKEN SWITCH OR WIRE AND I TENDED TO BELIEVE THE SAME THING GIVEN THEIR OBSERVATIONS AS WELL AS MY OWN. ON TOP OF THAT; I TRIED EVERY CONCEIVABLE OPTION TO GET THE GEAR DOWN AND GET A GREEN LIGHT; I RECYCLED THE GEAR; CHKED THE HYD FLUID IN THE RESERVOIR; MANUALLY PUMPED THE GEAR DOWN; VERIFIED THE GREEN LIGHT WAS NOT BURNED OUT; ETC. THIS WHOLE TIME I WORKED WITH THE TWR VERY CLOSELY AND WAS ABLE TO STAY OUT OF THE WAY OF OTHER TFC THEY WERE WORKING. FORTUNATELY THEY WERE NOT BUSY WORKING MANY FLTS AT ALL. AFTER REVIEWING THE CHKLIST FOR 'LNDG WITHOUT PROPER INDICATION OF THE GEAR BEING DOWN;' I INFORMED THE TWR THAT WHEN THEY GET A CHANCE I WOULD LIKE TO GO AHEAD AND ATTEMPT A LNDG. THEY ASKED ME IF THEY COULD GET SOME PLANES IN TO LAND BEFORE ME IN CASE I HAD TO CLOSE DOWN THE RWY. I SAID CERTAINLY BECAUSE I WAS IN NO HURRY (AT THIS POINT I STILL HAD ABOUT 4 HRS OF FUEL LEFT). WHEN THEY HAD A BREAK IN THE INCOMING TFC I ASKED FOR AND RECEIVED CLRNC FOR A LOW PASS TO CHK OUT THE WINDS. ON APCH I HAD NOTICED THAT THE CRASH TRUCKS AND RESCUE TEAM WAS WAITING ON ALL THE TXWYS FOR ME. I DID MY PASS AND CAME BACK AROUND TO LAND. FORTUNATELY THE WINDS WERE 170 DEGS AT 18 KTS AND I WAS LNDG RWY 17; SO I FELT VERY COMFORTABLE WITH THAT. I MADE A NORMAL FULL FLAP APCH AND SOFT FIELD LNDG. WHEN MY MAIN WHEELS WERE ON THE RWY I PULLED THE MIXTURE OUT AND KEPT THE NOSE OFF AS LONG AS POSSIBLE AND AS I WAS SLOWING DOWN I LOWERED IT VERY SLOWLY. MY GND SPD ON TOUCHDOWN COULD NOT HAVE BEEN MORE THAN 30 KTS OR SO. I LANDED STRAIGHT AND ON THE CTRLINE SO I IMMEDIATELY REMOVED MY FEET FROM THE RUDDER PEDALS SO I WOULD NOT CAUSE A PROB BY STEERING OR BRAKING. AS THE ACFT SLOWED DOWN ON THE RWY I PROCEEDED TO COMPLETE THE CHKLIST ITEMS BY SHUTTING OFF THE FUEL; MAGNETOS AND MASTER SWITCH. AFTER THE AIRPLANE CAME TO A STOP I EXITED AND EVERYTHING APPEARED TO BE NORMAL; ALL THE GEARS STAYED DOWN. THE CRASH AND RESCUE TEAM RESPONDED HOWEVER FORTUNATELY THEY WERE NOT NEEDED. AFTER THE PLANE WAS TOWED TO MAINT AND PUT UP ON JACKS IT WAS FOUND THAT THE L MAIN WASNEVER LOCKED DOWN. THE L MAIN DOWN LOCK NEVER MOVED INTO PLACE. THEREFORE; THE SWITCH WAS NEVER TRIPPED; THE GREEN LIGHT NEVER CAME ON AND THE PUMP CONTINUED TO RUN. THE NOSE GEAR DOORS STAYED OPEN BECAUSE THEY WAIT FOR THE GREEN LIGHT BEFORE THEY CLOSE. AS IT TURNED OUT; THE L MAIN DOWN LOCK ACTUATOR O RINGS WERE BAD SO THEREFORE THAT IS WHAT DIDN'T OPERATE PROPERLY.