SMA SPI HAS CIRCUIT BREAKER ON GEAR POP WHEN TRYING TO EXTEND THE LNDG GEAR. AFTER SEVERAL TRIES HE DOES GET 3 GREEN AND ON LNDG; GEAR COLLAPSES. ACFT EQUIP PROB LNDG GEAR COLLAPSE.

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AFTER A THOROUGH PREFLT INSPECTION AT OR ABOUT XA00 LCL TIME; USING THE MANUFACTURER'S CHKLIST; I DEPARTED TO PRACTICE SOME TOUCH AND GOES. ON DOWNWIND; THE AIRSPD INDICATOR MALFUNCTIONED AND I DECIDED TO LAND AND HAVE THE INST CHKED OUT BY MECHS. UPON THE USUAL GUMP CHK; THE LNDG GEAR DID NOT WANT TO COME DOWN; POPPING THE CIRCUIT BREAKER (NO 3 GREEN LIGHTS). THE SAME HAPPENED ON BASE AND FINAL. I DID A GAR AND THE BREAKER POPPED OUT IN DOWNWIND AND BASE AGAIN. ON FINAL I GOT THE 3 GREEN LIGHTS AND I DECIDED TO LAND AT THE USUAL AND NORMAL APCH AND LNDG SPD USING VISUAL REF AND SOUND AS TRAINED TO DO AND AS I HAVE ALWAYS DONE IN THE PAST. BEING VFR I DEPEND MORE ON OUTSIDE REF THAN INSTS. I HAD A SIMILAR PROB FEW MONTHS AGO AND THE MANUFACTURER HAD TO SEND ME A NEW SET OF LIGHTS AND WERE INSTALLED ACCORDINGLY. WHEN I TOUCHED BEYOND THE NUMBERS; THE MAIN GEAR COLLAPSED FORCING ME TO SKID DOWN THE RWY. I CAME TO AN ABRUPT STOP. THEREAFTER; AND CALMLY; I TURNED OFF ALL SWITCHES; THE FUEL SELECTOR WAS TURNED OFF; UNFASTENED MY SEAT BELTS AND WALKED OUT.