Incident Overview
A student pilot, who was the lessee of the airplane, conducted airwork with a certified flight instructor (CFI) on board. After completing the airwork, the CFI took control of the airplane for the return and landing. The CFI reported that while over the runway, controllability via the yoke was suddenly lost. He asked the student to pull on the yoke, but there was no response. The airplane touched down on all three landing gears, bounced, and after a second touchdown, the CFI applied rudder input. The airplane then departed the runway onto the grass. Evidence of a hard landing was noted.
Yoke Weld Assembly Examination
Post-incident examination revealed that the yoke weld assembly was completely fractured approximately 5.5 inches from its bottom, about 5/32 inch above the yoke pivot point. Extensive corrosion was present from the fracture location downward approximately 3 inches on the forward and left sides of the exterior surface of the lower separated piece, as installed in the airplane. Corrosion was also noted on the lower end of the yoke weld assembly, which contains a rod end bearing and is the attach point for the elevator push/pull tube; the rod end bearing was not free to move. No drain hole was found in the separated lower portion of the vertical tube. Corrosion was also observed on the gusset areas of both the pilot's and copilot's sides. The interior of the separated lower vertical tube appeared filled with a substance composed mainly of iron and oxygen. Debris from the separated upper portion contained an abundance of iron oxide, without significant inorganic material.
Other Findings
Small leaves, metal shavings, fasteners, grass, and dirt were found on the interior surface of the lower fuselage skin in the cockpit area. Similar debris (small leaves, grass, dirt) was found inside the battery box. Mold (white and green powder) was found on the cockpit side of the firewall insulation blanket.
Examination of the two sections of the yoke weld assembly by Cessna Aircraft Company indicated that the wall thickness near the separation point was reduced to near zero. Material composition was correct, and hardness tests showed values greater than the minimum specified. Evidence of water marks was noted on the upper portion of the separated vertical tube.
Aircraft History
The airplane had been partially submerged in salt water as a result of Hurricane Floyd in September 1999, with the water level reportedly reaching up to the battery. The airplane was subsequently sold as salvage, and the then owner reported to the FAA that the airplane was "destroyed/scrapped." It was later re-registered with the FAA, but no entry was made in the maintenance records indicating the partial submersion; none was required.
The last inspection was an annual/100-hour inspection conducted using the Service Manual checklist. The Service Manual indicates that the control "U" is listed for inspection in the 200-hour column. The airplane had accumulated approximately 12 hours since that inspection at the time of the incident. According to Cessna Aircraft Company personnel, there is no inspection in the service manual required for aircraft that become partially submerged or submerged in salt water. Additionally, review of Advisory Circulars revealed no inspection criteria or advice for such situations.