C210 BECAME DISTR AND FORGOT TO PUT THE LNDG GEAR DOWN.

Narrative

WHILE ON THE LNDG APCH TO FNT ARPT; RWY 27; I WAS REQUESTED TO RPT MY INDICATED AIRSPD (100 KIAS). I DID SO; BUT WAS WARY OF THE REASONS FOR THIS; IE; WAS THERE AN AIRPLANE GAINING ON ME OR WAS I GAINING ON ANOTHER ACFT? I INCREASED MY OUTSIDE SCAN BUT COULD SEE NO OTHER ACFT. SHORTLY THEREAFTER; I WAS CLRED TO LAND FOLLOWING ANOTHER ACFT ON SHORT FINAL. I COULD NOT LOCATE THE OTHER AIRPLANE. WHEN I FINALLY DID LOCATE THE OTHER ACFT IT WAS NEARING TOUCHDOWN AND I WAS ON SHORT FINAL. I RPTED THE ACFT IN SIGHT. AT ABOUT THIS TIME THE RADAR ALTIMETER IN MY ACFT WENT OFF (AN INDICATOR LIGHT AND SOUND). I NORMALLY DO NOT USE THIS BUT I DID CHK IT AND TRIED TO TURN IT OFF. AFTER THIS; I WAS APCHING THE RWY THRESHOLD AND DID MY ROUND-OUT AND FLARE WITH EYES FIXED WELL DOWN THE RWY. UNFORTUNATELY; I NEGLECTED TO EXTEND THE LNDG GEAR. I BELIEVE THE CAUSE OF THIS INCIDENT WAS ALLOWING MYSELF TO BE DISTR FROM MY NORMAL ROUTINE. NORMALLY; I DO SEVERAL ROUTINE CHKS ON THE LNDG GEAR. THESE SERIES OF SMALL DISTRS BROKE MY NORMAL ROUTINE LEAVING ME VULNERABLE TO THIS GEAR UP LNDG.