Accident Summary
On June 23, 2017, about 1600 mountain standard time, a Cessna U206F airplane, registration N71001, sustained substantial damage during a precautionary landing approximately 28 miles southeast of Page, Arizona. The two commercial pilots and four passengers were not injured. The airplane was registered to and operated by American Aviation Inc. as a Title 14 Code of Federal Regulations Part 135 scenic flight. Visual meteorological conditions prevailed, and a company visual flight rules flight plan had been filed. The flight originated from Page, Arizona at an unknown time.
Flight Sequence
The pilot in command reported that while returning to the airport at 7,500 feet, the airplane would no longer climb and began a slow descent at about 350 feet per minute. Unable to stop the descent, the pilots attempted to troubleshoot but could not restore engine power. The pilot initiated a precautionary landing onto a dirt road. About 125 feet above ground level, the co-pilot took control and landed softly on the road. During the landing roll, the airplane's left wing impacted juniper bushes before coming to rest. As the pilots retarded the throttle to idle, the throttle lever came out of the control panel along with approximately two feet of throttle cable.
Postaccident Examination
A Federal Aviation Administration inspector noted that the throttle control cable had separated from the rod end of the throttle body control. Review of maintenance logs indicated that the throttle cable was last installed in 1996. The throttle cable, including the rod end and rod end sleeve, was sent to the National Transportation Safety Board (NTSB) Materials Laboratory for examination.
Laboratory Findings
The NTSB Materials Laboratory reported that digital microscope images of the rod end, which was within the rod end sleeve, exhibited two circumferential bands of wear on the ends. The bands were heavier on one side of the pieces, and the band closest to the end had less damage compared to the other band. Corresponding wear was observed on the inner surface of the mating guide piece. The wire strands were observed, and the fracture surfaces were flat and perpendicular to the axes of the strands. No necking or thinning of the individual strands consistent with overstress separation was observed.
Maintenance Background
The Cessna Maintenance Manual indicates that engine controls and linkages should be examined every 50 hours for general condition and freedom of movement, and that controls are not repairable; they should be replaced at each engine overhaul. The operator reported that the airplane's annual inspection was completed about 43 hours prior to the accident, and the overhaul occurred 163 hours prior. The logbooks did not show that the cable had been replaced.