SMT UNDERSHOOTS RWY; PLOWS THROUGH SNOW BANK AND L MAIN GEAR COLLAPSES DURING LNDG ROLLOUT.

Narrative

ON FINAL APCH THE ACFT DEVELOPED A HIGH SINK RATE AND LANDED ABOUT 30 FT SHORT OF THE THRESHOLD. IT HAD SNOWED HEAVILY 2 DAYS EARLIER AND THE ACFT ROLLED THROUGH A 2-3 FT HIGH SNOW BANK AT THE RWY THRESHOLD WHICH SHEARED A BOLT IN THE L MAIN GEAR. AT ABOUT 900 FT DOWN THE RWY THE BOLT FELL OUT OF THE GEAR CAUSING THE ACFT TO SETTLE ON THE L ENG NACELLE. THE ACFT CAME TO REST ON A SNOW BANK ON THE L SIDE OF THE RWY WITH DAMAGE TO THE PROP AND FLAP ON THE L SIDE IN ADDITION TO THE SHEARED BOLT. THE LCL AUTHORITIES AND THE FAA GADO INSPECTOR RESPONDED AND DOCUMENTED THE INCIDENT. THIS RWY IS CLOSELY BOUNDED ON BOTH SIDES BY WOODS. AT THE TIME OF THE INCIDENT THE WIND WAS ABOUT 10-13 KTS AT 45 DEGS ACROSS THE RWY. AS THE ACFT DSNDED BELOW 200 FT AGL THE WIND SHEARED OFF RAPIDLY BEHIND THE TREES. THIS LED TO A RAPID DECREASE IN AIRSPD AND RAPID INCREASE IN SINK RATE WHICH I DID NOT FULLY PERCEIVE UNTIL THE ACFT HAD GOTTEN 'BEHIND THE PWR CURVE.' I WAS AWARE OF AN INCREASE IN SINK RATE BUT I DID NOT ADD SUFFICIENT PWR TO OVERCOME IT AS; FOR THE REASONS STATED ABOVE; I DID NOT PROPERLY JUDGE HOW EXCESSIVE IT HAD BECOME UNTIL IT WAS TOO LATE TO RECOVER.