On September 4, 2006, at approximately 1400 mountain daylight time, a Straw T-Bird II experimental homebuilt airplane, N339JL, was substantially damaged following impact with terrain near Leamington, Utah. The private pilot, the sole occupant on board, was seriously injured. The pilot/owner was operating the flight under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the local flight; the origination time was undetermined. The pilot had not filed a flight plan. Witnesses observed the airplane flying low to the west. They said it started a left turn and continued until it nosed down to the ground. They reported hearing a loud engine sound all the way until impact. A friend of the pilot examined the aircraft and found the inboard bolt on the left elevator bow was missing, and the outboard bolt was failed in a sheared/twisting mode. The reason that the bolt was missing was undetermined.