Amateur-built BI-PLANE N375CB accident near Caldwell, Idaho

Probable cause

Loss of control during the landing roll for undetermined reasons.

NTSB analysis

The pilot reported that during a routine test flight, he felt an abnormal vibration and decided to divert to a nearby airport. After noting the wind conditions, the pilot entered the airport traffic pattern and proceeded to execute a wheel landing in the tailwheel-equipped airplane. As the tailwheel settled onto the runway, the airplane immediately veered to the right. Despite the pilot's control and brake inputs, the airplane continued to veer to the right and exited the runway. Subsequently, the airplane came to rest in a nose-low attitude adjacent to the runway surface. Examination of the airplane by a Federal Aviation Administration inspector revealed that the left and right top and bottom wing assemblies and fuselage were structurally damaged. Flight control continuity was established throughout the airplane to all flight controls. Movement of the tailwheel by hand revealed that it locked into its normal turning radius and subsequently broke free with little pressure. No anomalies could be found with the airframe; however, examination of the runway revealed a black rubber transfer mark with a width corresponding to the width of the airplane's tailwheel. The mark was not linear, but had a zigzag shape consistent with the tailwheel shimmying.

Text from the NTSB. Open the NTSB docket for WPR09LA201 for the full record.