While conducting a personal flight, the pilot reported he experienced a “complete loss of flight controls” during the landing flare.
The main landing gear settled to the runway at the airport in Harvard, Illinois.
During the landing roll, he was able to reach the copilot-side control yoke in the Cessna 170 and complete the landing, but the airplane received substantial damage.
A post-accident examination of the airplane revealed that the rivet in the universal joint for the pilot-side control yoke had failed, causing the universal joint to disassemble.
The examination of the universal joint also revealed that the assembly seized and would not articulate as designed. The assembly seized due to galling wear between the center pin and the yoke ear holes and between the swivel blocks and the yoke ears, resulting in high alternating stresses in the rivet that held the half pins in place. The high alternative stresses in the rivet caused the rivet to fail by low-cycle reversed-bending fatigue fracture. The universal joint design was prone to galling wear and seizure.
Maintenance records indicated the universal joint had been replaced 1.5 years before the accident and had acquired 199.1 hours of flight time since being installed. The component had been maintained in accordance with the requirements prescribed in the airframe manufacturer’s service manual. No evidence suggested that the failure was related to improper maintenance or lubrication.
Probable cause: The failure of the universal joint in the pilot-side flight control yoke due to the fatigue fracture of a rivet within the universal joint. Contributing to the universal joint failure was the universal joint design, which was prone to galling wear and seizure.
NTSB Identification: CEN18LA044
This November 2017 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.