On August 8, 2000, about 1730 Eastern Daylight Time, a Piper PA28-235, N8809W, was substantially damaged while landing at the Chester Airport (3B9), Chester, Connecticut. The certificated flight instructor (CFI) and private pilot received minor injuries. Visual meteorological conditions prevailed and no flight plan had been filed for the local instructional flight conducted under 14 CFR Part 91. The private pilot was performing a soft field landing as part of a biennial flight review that was being conducted by the CFI. The airplane was on approach to Runway 17, a 2,566 foot long, asphalt runway, with a displaced threshold of 559 feet. According to the CFI, when the airplane was on "short final," the airplane entered a "down draft that greatly increased the sink rate." As he started to order a go-around, the private pilot applied full engine power and raised the airplane's nose; however, the airplane contacted bushes and a fence located prior to the runway threshold. A witness waiting for takeoff at the Runway 17 "hold-short" line stated that the airplane looked "low and slow" while on final approach. As the airplane continued to descend towards the fence which preceded the runway, he observed the airplane "pitch up abruptly" and then suddenly pitch back down. He was not able to hear the airplane. Examination of the wreckage by a Federal Aviation Administration inspector, did not reveal any pre-impact malfunctions, nor did the pilots report any. Winds reported at an airport about 24 miles east of 3B9, at 1756, were from 240 degrees at 6 knots.