On September 20, 1995, about 1600 Alaska daylight time, a float equipped Maule M-7-235 airplane, N56564, sustained substantial damage when it collided with terrain approximately 50 miles east of Aniak, Alaska. The commercial pilot and two passengers aboard were not injured. The 14 CFR Part 135 on-demand Air Taxi flight operated in visual meteorological conditions without a flight plan. The flight had just departed an unnamed lake located in a box canyon en route to Aniak when the accident occurred. The pilot reported he landed on the lake to pick up three hunters. He said he made one flight from the lake prior to the accident flight. The initial flight and the accident flight were made towards the interior of the box canyon. The pilot said he elected to takeoff towards rising terrain because of favorable wind conditions in that direction. He estimated the wind as 7 to 10 knots from the southeast. The initial flight was flown with one hunter and some baggage aboard. This flight was flown without incident. The accident flight was made a short time later. No unusual wind activity on the lake was observed at the time of departure. During the initial climb phase, the pilot said he encountered a strong gust of wind estimated at 40 knots, and an associated downdraft that would not allow the airplane to climb away from the rising terrain. He said he slowed the airplane and elected to make a landing in the tundra in lieu of continuing the flight into higher terrain. The airplane sustained substantial damage to the airframe structure during the landing.