PLT OF AN SMA SEL RETRACTABLE LNDG GEAR ACFT LANDED GEAR UP. ONLY MINOR DAMAGE TO THE ACFT AND NO INJURY TO THE SOLO OCCUPANT; THE PLT.

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HELI PLT CONVERTING BACK TO FIXED WING. PREVIOUS FLT EXPERIENCE (250 HRS). ALL ON FIXED GEAR. THIS WAS A NEW ACFT/NEW FIELD SIT. GEAR HORN RECENTLY ADJUSTED TO 12 PSI (WAS 22 PSI FOR FIRST 7 HRS). I SLOWED THE ACFT TO 120 MPH ABOUT 12 MI OUT AND IN MY MIND PUT THE GEAR DOWN. DSNDED TO CIRCUIT HT (1043 FT). JOINED 45 DEG TO DOWNWIND. DID GUMP CHKS (OBVIOUSLY POORLY). CONVINCED GEAR WAS DOWN BUT DID NOT CHK PROPERLY. TURNED FINAL. CONCERNED ABOUT BEING A LITTLE LOW; USED THROTTLE. FAILED TO DO FINALS GEAR CHK. DIDN'T HEAR GEAR HORN. ACTUALLY KEPT PWR ON UNTIL LAST 10 FT. WAS WEARING HELI HEADPHONES. DID A 'GREASE-ON' LNDG WITH SLIGHT STALL WARNING. TOTALLY SHOCKED TO HEAR THE DREADED SCRAPING SOUND!! NO DOUBT PLT ERROR; BUT SOME THOUGHTS IN RETROSPECT: MUST DO 'TOUCH IT' GUMP CHKS. MUST GET INTO A 'GROOVED' PROC. WOULD BE GOOD TO HAVE 'GEAR UP' AND 'STALL' WIRED INTO HEADSET. 'GEAR UP' AND 'STALL' WARNINGS SHOULD BE DISTINCTLY DIFFERENT SOUNDS. THANKFULLY I WAS THE ONLY PERSON ON BOARD AND NOT HURT. DAMAGE NOT TOO BAD. FAA CLASSED AS AN 'INCIDENT.'