Thrush S2R N32LF accident near Talkeetna, Alaska

Probable cause

The pilot's improper landing in the tailwheel-equipped airplane, which allowed an excessive load on the tailwheel and resulted in the subsequent component fracture, loss of control, runway excursion, and impact with terrain.

NTSB analysis

The pilot was transporting bulk fuel to a remote lodge. During the landing to the dirt and gravel runway, the tail of the airplane came down, and the pilot heard a loud bang. He reported the empennage "went clear" to the ground and that he had no rudder authority. The pilot attempted to control the airplane, but the airplane departed the runway and impacted a ditch, which resulted in substantial damage to the left wing, fuselage, and empennage.

The tailwheel spring assembly and a fractured attachment bolt were recovered from the airplane. An examination revealed that the deformation of the bolt and appearance of the fracture surface were consistent with bending overstress. The spring and a portion of the bolt exhibited corrosion and pitting; signs of fatigue were not noted.

The airplane flight manual states to lower the tail smoothly during the landing roll. Because the deformation of the bolt and the fracture surface were the result of overstress, it is likely that the pilot allowed an excessive landing load on the tailwheel when it touched down, which resulted in a loss of control and a subsequent runway excursion and impact with terrain.

Text from the NTSB. Open the NTSB docket for ANC17LA046 for the full record.