WPR20LA054

The pilot reported that the approach and landing flare were normal; however, as he moved both throttles to the beta position, it appeared that the left propeller went into the beta position while the right one did not. This resulted in a course deviation and runway excursion to the left, which led to the separation of the right main landing gear and substantial damage to the right wing. The National Transportation Safety Board was unable to conduct a follow-up examination, as the airplane has been sold and a chain of custody had been compromised. As a direct result of the airplane not being able to be examined, the cause of the right propeller failure to correspond to the throttle movement to the beta position is undetermined.

On December 30, 2019, about 1445 mountain standard time, a Mitsubishi MU-2-60 airplane, N43866, was substantially damaged when it was involved in an accident at the Miley Memorial Field Airport (BPI), Big Piney, Wyoming. The private pilot and three passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the approach was normal, and he did not experience any issues when the airplane made contact with the runway. However, as he moved both throttles to the beta position, it appeared that the left propeller went to beta position while the right one did not. This resulted in a course deviation about 30°- 35°. An attempt to correct the drift with the nose gear control was unsuccessful. The airplane departed the runway and began to turn which, led to the separation of the right main landing gear, collision of the right wing with terrain, and the right-wing tip separation. The airplane came to rest off the left side of the runway with the nose of the airplane oriented towards the approach end. The airplane was secured and retained at BPI for further examination. The airplane was subsequently sold and removed from the airport before an examination could be coordinated.