The pilot stated that the approach to landing was routine, flown with two notches of flaps, and airspeed steady at 80 knots. The pilot said the airplane appeared to be landing long, so he selected the last notch of flaps. Immediately afterward, he observed that the airspeed had decayed to 60 knots and the airplane had developed a high sink rate. The pilot applied full power but was unable to arrest the descent. The airplane impacted terrain approximately ten feet short of the runway threshold sustaining in substantial damage. An examination showed the left wing was fractured and mostly separated from the airframe just outboard of the fuselage. The left main landing gear and nose gear had collapsed and the propeller was bent. The pilot stated that the weather was clear, there was no wind, and there were no mechanical anomalies with the airplane prior to the accident. An examination of the airplane by a Federal Aviation Airworthiness Inspector confirmed no mechanical anomalies.