On March 19, 2000, about 1500 Eastern Standard Time, a Cessna 172, N6261E, was substantially damaged during an approach to Black Rock Airport (PA234), New Brighton, Pennsylvania. The certificated airline transport pilot and his two passengers were uninjured. Visual meteorological conditions prevailed at the time of the accident. No flight plan had been filed for the personal flight, conducted under 14 CFR Part 91. The pilot stated that the airplane was making an approach after a local-area flight, towards the east, to an east-west grass airstrip. The wind appeared to be steady, down the runway. On final approach, wind conditions became "choppy", and, "on very short final, reducing speed for short field landing, [the] wind sheared downward. Also, wind velocity went to zero. Aircraft was forced downward." As the pilot felt the downward force, he added full power and pitched nose-up to initiate a go-around. However, the airplane continued to sink rapidly, caught treetops, then "mushed" into the ground about 20 feet short of the runway. The runway was about 1,500 feet in length, and 75 feet wide. The approach was flown over a valley, with the final segment flown over an up-slope of a hill. The runway threshold was on top of that hill. A weather observation at the approximate time of the accident, at an airport about 5 nautical miles away, included winds from 120 degrees true, at 16, gusting to 30 knots. The seven previous hourly observations included winds at 18 to 20 knots, with six of those having gusts at or above 30 knots. The pilot had about 9,000 hours of flight time, and was a captain for a major air cargo carrier.