PLT OF AN SMA SEL ATX CARGO ACFT EXPERIENCED LNDG GEAR COLLAPSE DURING LNDG TOUCHDOWN.

Narrative

THIS ACCIDENT HAPPENED ON THE FINAL LEG OF A 4 LEG ROUND ROBIN PART 135 CARGO FLT. THE LEG ON WHICH THIS ACCIDENT OCCURRED WAS FROM IND TO STL. IT WAS A ROUTINE FLT. I HAD BEEN CLRED FOR THE VISUAL APCH TO RWY 24 AT STL APPROX 27 NM OUT. WHILE TRACKING THE LOC AND THE GS; AND APCHING THE OM; I REFED THE BEFORE LNDG CHKLIST FOR THE SMA. AT THE OM; I SELECTED APCH FLAPS AND LNDG GEAR DOWN. HOLDING THE GEAR LEVER IN THE DOWN POS I VISUALLY SAW THE L MAIN GEAR COMING DOWN AND LOOKED BACK AT THE POS LIGHTS WHERE THE GREEN GEAR DOWN LIGHT ILLUMINATED. I CHANGED RADIO FREQS TO TWR AND WAS CLRED TO LAND ON RWY 24 AND TO HOLD SHORT OF RWY 30L. AT THE MIDDLE MARKER I SELECTED FULL FLAPS WITH A SHORT FIELD TO NORMAL LNDG IN MIND TO TURN OFF WITHIN THE 4000 FT OF RWY AVAILABLE. THE FLARE TO LNDG APPEARED NORMAL; THERE WAS NO GEAR UNSAFE HORN ON AND THE TOUCHDOWN WAS NORMAL; EXCEPT THE ACFT FELT LIKE IT BOUNCED A COUPLE OF FT AND WAS SETTLING BACK TO THE RWY. I BELIEVE THIS FEELING WAS ACTUALLY THE MAIN LNDG GEAR TOUCHING THEN COLLAPSING; THUS THE SINKING BACK TO THE RWY FEELING. AFTER THIS LNDG I SAW LIGHT FROM MY PERIPHERAL VISION. AS I TURNED MY HEAD I SAW SPARKS COMING FROM THE TAIL TIE-DOWN. AT THIS POINT; I NOTIFIED TWR OF THE SIT AND PROCEEDED TO SECURE THE ACFT. AFTER THE ACFT CAME TO REST; I ESCAPED THROUGH THE R PAX DOOR AND FOUND NO FIRE; BUT THE L WING TIP AND L HORIZ STABILIZER WERE DAMAGED.