N71001Cessna U206F · 1973

On June 23, 2017, about 1600 mountain standard time, a Cessna U206F airplane, N71001, sustained substantial damage after the pilot executed a precautionary landing about 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 at the time of the accident and a company visual flight rules flight plan had been filed. The flight originated from Page, Arizona at an unknown time.

The pilot in command (PIC) reported that while they were returning to the airport at 7,500 ft, the airplane would no longer climb; it then slowly started to descend at about 350 ft per minute. Unable to stop the descent, the pilots attempted to troubleshoot the problem, but were not able to restore engine power. The PIC initiated a precautionary landing onto a dirt road. About 125 ft above the ground, the co-pilot took control of the airplane and landed softly onto the road. During the landing roll, the airplane's left wing impacted juniper bushes before it came to rest. As the pilots retarded the throttle to idle, the throttle came out of the control panel along with about two ft of the throttle cable.

During a postaccident examination by a Federal Aviation Administration inspector, it was noted that the throttle control cable separated from the rod end of the throttle body control. Review of the maintenance logs indicated the throttle cable was last installed in 1996.

The throttle cable, to include the rod end, and rod end sleeve were removed from the airplane and sent to the National Transportation Safety Board (NTSB) Materials Laboratory for further examination.

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.

Cessna Maintenance Manual indicates that the engine controls and linkages should be examined "each 50 hours for general condition and freedom of movement. These controls are not repairable. Replace throttle, propeller, and mixture controls at each engine overhaul." The operator reported the airplane's annual inspection was completed about 43 hours prior to the accident, and the overhaul 163 hours prior to the accident. The logbooks did not show that the cable had been replaced.