What happened
During a descent, the pilot of a Cessna 210 experienced "extreme pressure" when attempting to pull back on the controls to level the aircraft. Due to this resistance, the pilot was unable to maintain altitude and continued on a straight-in approach to the airport. During the landing flare, the pilot could not pull the control yoke far enough to round out the approach. Consequently, the airplane landed hard on the nosewheel and came to rest off the side of the runway. The pilot was not injured.
The investigation
A flight control check performed after the accident demonstrated that the controls could only be deflected aft to the "level flight" position. Upon removing the Horizontal Situational Indicator (HSI) from the instrument panel, the flight controls could be moved to their full aft position.
Investigators found significant chafing marks and black paint transfer on the upper surface of the control stop on the control column tube. Similar chafing and an indentation matching the shape of the control column stop were found on the lower edge of the HSI rear casing.
Further examination of the instrument panel revealed five installed shock mounts in various states of failure: the lower right and lower center mounts were broken, and the upper left mount was not attached. The remaining mounts showed fractures through their elastomeric center sections, large gaping cracks on one end, and numerous small circumferential cracks throughout the center sections. Maintenance logs indicated the HSI had been installed on August 17, 1994, to replace a directional gyro; however, the examined shock mounts were the original components installed in December 1963.