On October 24, 1995, at 1745 Alaska daylight time, a float equipped Piper PA-18-150 airplane, N2399S, registered to the pilot's father, and operated by the pilot, experienced a downdraft while attempting to fly through "Powerline Pass" which is located 12 miles east of Anchorage, and crashed into the east side of the pass. The personal flight, operating under 14 CFR Part 91, last departed Lake Hood Seaplane Base, Anchorage, Alaska, for a local flight. No flight plan was filed and visual meteorological conditions prevailed. The certificated airline transport pilot, the sole occupant, was not injured and the airplane received substantial damage. During a telephone conversation with the pilot on October 25, 1995, he stated that he was attempting to cross through the pass east to west. As he neared the pass, a severe downdraft started to push the airplane toward the ground. He was unable to recover and the airplane struck the ground. The pilot could not estimate the winds at the accident site. The Lake Hood Automatic Terminal Information System (ATIS)information showed that the airport winds were from the north at 5 knots. There were no weather or wind reporting facilities near the pass.