On September 2, 2000, approximately 1800 Pacific daylight time, an Ercoupe 415-C, N87351, collided with trees just off the approach end of a private airstrip near Wapato, Washington. The private pilot received serious injuries, his passenger received minor injuries, and the aircraft, which was owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 91 personal pleasure flight, which departed Sunnyside Municipal Airport, Sunnyside, Washington, about 30 minutes prior to the accident, was being operated in visual meteorological conditions. No flight plan had been filed, and there was no report of an ELT activation. In a post-accident conversation with a Federal Aviation Administration Operations Inspector, the pilot, who based the aircraft at the private strip, said that while on final approach, he inadvertently allowed the aircraft to descend lower than normal. When he was about 50 feet from the approach end of the airstrip, he realized that he would need to climb in order to clear the trees that were located just short of the runway. Although he added power, he had done so too late to enable the aircraft to climb above the treetops. Therefore, the aircraft struck the trees and nosed over into the terrain. The pilot further stated that he thought he may have encountered a downdraft at about the time he added power. He said that he was not aware of any problems with the airframe, flight controls, or the engine.