ANC94LA039

The pilot said he attempted to fly 'up valley' when he encountered downdrafts. He applied full power to maintain altitude but did not have enough airspeed to turn out of the valley. Unable to maneuver out of the valley the pilot made a landing in deep snow on a steep incline at the 3000 ft level, 100 feet below the ridge line.

On March 7, 1994, at approximately 1515 Alaska standard time, a wheel-equipped Cessna 170B airplane, N4310B, collided with mountainous terrain while attempting to out climb a downdraft in a valley eight miles east of Birchwood Airport, Chugiak, Alaska. The airplane departed the Birchwood Airport at approximately 1500 on a local flight for personal reasons. No flight plan was on file for the flight conducted under 14 CFR Part 91 in visual meteorological conditions. The private pilot and his three passengers were not injured and the airplane sustained substantial damage.

The pilot told the NTSB and an FAA inspector that he encountered a mountain downdraft as he climbed southbound in the valley which forced him into a controlled collision with the snow-covered ridge. He said that he had been flying with his wife and two children on a local sightseeing flight when the force of the wind exceeded his aircraft's ability to avoid a collision with the terrain. He told investigators that he had checked the weather by "listening on the Big Lake VOR;" however, he could not recall the forecast or observation at the time of the interview. The impact occurred at the 2,900 foot level of a 3,000 foot ridge.

Following the impact with the snow-covered ridge, the family waited at the wreckage until a passing snowmobile driver sighted them and brought them to safety. The pilot said that while awaiting rescue, the winds were from the south at 25 knots with higher gusts.

In a written statement from the pilot the NTSB learned that the pilot had attempted to fly the airplane "up valley," when at the halfway point, he said that he encountered severe down drafts, applied full power to maintain altitude but did not have enough airspeed to attempt a turn out of the valley. After continuing in up drafts and downdrafts the pilot made a forced landing in deep snow and a steep incline at the 3000 foot level, 100 feet below the ridge line.