SEA96LA143

The pilot stated that while on approach to runway 21, he encountered crosswind conditions and added power to extend the landing; just before touchdown, an extremely strong gust blew the aircraft to the right of the runway. The pilot said he added full power to initiate a go-around. The aircraft started to climb, then just started descending to the right. Subsequently, it went into the terrain 'sideways,' but upright. The pilot noted that an individual in the area had observed strong wind gusts with changing directions on the morning of the accident. The airport had high timbered ridges to the east of the runway. Density altitude was approximately 9,400 feet.

On July 5, 1996, approximately 1200 mountain daylight time, a Taylorcraft BC12-D, N95658, was substantially damaged in a collision with terrain during an attempted landing at Twin Bridges Airport northeast of Sun Valley, Idaho. The commercial pilot, who had private privileges for single-engine airplanes, received minor injuries and a passenger sustained serious injuries. Visual meteorological conditions existed and no flight plan had been filed for the 14 CFR 91 flight from Smiley Creek Airport near Stanley, Idaho.

The pilot stated in his accident report that on approach he encountered some crosswinds and added power to extend the landing; just before touchdown, an extremely strong gust blew the aircraft sideways to the right of the runway. He said he added full power to initiate a go-around. The aircraft started to climb approximately 50 feet, then just started descending to the right and went into the terrain sideways but upright. The pilot noted that a cowboy in the area had observed strong wind gusts with changing directions on the morning of the accident. The airstrip, which runs northeast/southwest, has high timbered ridges along its east side according to an airport depiction filed with the FAA on-scene investigator's report. Winds at Hailey, approximately 32 miles south, were reported as being from 230 degrees magnetic at 10 knots at 1345.

Twin Bridges airport is a 4,450 by 100 foot turf strip at an elevation of 6,893 feet above sea level. Hailey, at an elevation of 5,315 feet, reported a temperature of 21 degrees C and an altimeter setting of 30.10 inches Hg in its 1345 observation. The pilot, in his accident report, estimated the temperature at the accident site as 75 to 80 degrees F at the time of the accident. Based on the field elevation of 6,893 feet, a temperature of 24 degrees C (75.2 degrees F), and the Hailey reported altimeter setting of 30.10 inches Hg, the density altitude at the accident site was computed to be 9,359 feet.

FAA inspectors noted that the pilot had stated that upon arriving in the Twin Bridges area, he circled the airport and then made an approach for runway 21. At that time, the wind sock was down the runway. There were no witnesses to the accident. After the accident, FAA inspectors discovered a broken left aileron hinge bracket. Upon inspection, no indication was noted of pre-accident failure of this component.