On August 29, 2000, about 1540 Alaska daylight time, a tundra tire equipped Piper PA-18 airplane, N125FG, sustained substantial damage after colliding with terrain, about 35 miles east of Port Heiden, Alaska, at latitude 56 degrees, 48.6 minutes north, and longitude 157 degrees, 34.8 minutes west. The airplane was being operated as a visual flight rules (VFR) government flight under Title 14, CFR Part 91, when the accident occurred. The airplane was registered to, and operated by, the State of Alaska, Department of Fish and Game, Kodiak, Alaska. The commercial certificated pilot, and the sole passenger, a State of Alaska biologist, received serious injuries. Visual meteorological conditions prevailed. VFR company flight following procedures were in effect. During an interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on September 6, 2000, the pilot reported he departed Chignik Lake airport, Chignik, Alaska, about 1000, to conduct salmon fish surveys in several streams on the Alaska Peninsula. Chignik is about 51 miles southwest of the accident site. He said that when they departed Chignik, the weather conditions included calm winds, and small clouds over high, mountainous terrain. After stopping for a break at Coho Beach, about 22 miles northeast of the accident site, the survey continued southwesterly at 1515 into the area of Amber Bay (40 miles east of Port Heiden). The wind began to blow from the southwest, disturbing the water surface of the bay and streams. The pilot decided to discontinue the survey and return to Chignik, heading in a southwest direction. The wind continued to increase with occasional turbulence. The pilot said he was in cruise flight about 1,200 feet msl in the area of a small saddle between two low hills, located between Amber Bay and Aniakchak Bay, along the east side of the Alaska Peninsula. As the flight approached the saddle, the airplane began to lose altitude in a strong downdraft. He added full power, but the airplane continued to descend. He observed trees below him that were being flattened by the downdraft. He attempted to turn right, away from the side of one small hill, but a sharply increased ground speed prompted him to turn back into the prevailing wind. The airplane continued toward the ground, and the pilot said he lowered the nose of the airplane into an area of tall alders to make contact with terrain with some degree of control. During the collision with the trees, the engine and firewall were torn off the front of the airplane, and the wings were displaced rearward. In a telephone interview with the NTSB IIC on September 5, 2000, the passenger reported that during the downdraft, his clipboard was pinned against the cabin roof. The closest official weather observation station is Port Heiden, located along the west side of the Alaska Peninsula. On August 29, 2000, at 1535, an automated weather observation system was reporting, in part: Wind, 240 degrees (true) at 36 knots, gusts to 41 knots; visibility, 8 statute miles; clouds and sky condition, few at 2,600 feet, few at 3,000 feet, 4,400 feet overcast; temperature, 52 degrees F; dew point, 40 degrees F; altimeter, 30.09 inHg.