STINSON 108-2

Full Narrative

On August 28, 2010, about 1835 Alaska daylight time, a Stinson 108-2 airplane, N9569K, sustained substantial damage during an off airport landing, about 48 miles west of Port Alsworth, Alaska. The airplane was being operated by the pilot as a visual flight rules personal cross-country flight under the provisions of 14 Code of Federal Regulations Part 91, when the accident occurred. The commercial pilot and the two passengers were not injured. Visual meteorological conditions prevailed, and company flight following procedures were in effect. The flight departed Port Alsworth about 1730.

In a written report to the National Transportation Safety Board (NTSB) dated September 6, the pilot reported that he was taking his sons on a camping trip. He reported that after scouting a ridge west of Port Alsworth, he decided to land since it was a familiar tundra landing area that he had used in the past. He said he flew over the landing area three times to gauge wind conditions, and to be sure there were no new obstacles to be avoided in the landing area. After touching down and braking almost to a stop, he said he was taxiing into the area where he planned to park, when the right wheel broke, and the plane tipped on its right wing. He said the right wing, wing spar, and aileron were damaged when the wing struck the ground.

On September 2, the NTSB investigator-in-charge (IIC) examined the broken wheel. The wheel had been mounted with 35 inch Alaskan Bush Wheels. The center of the wheel casting adjacent to the inner bearing race had fractured around its circumference, and the casting piece and bearing race had separated from the wheel, allowing the axle to pivot.

On February 16, 2011, an examination of the fractured wheel was completed at the National Transportation Safety Board's materials laboratory. The investigation revealed features indicative of overstress separation of the flange. No indications of fatigue, corrosion or other preexisting conditions were noted.