CEN17LA216 · William D Telfair/ZIA Z Telfai EXCALIBUR

The commercial pilot was conducting a personal flight in the experimental amateur-built airplane. After about 1 hour of flight, the airplane was straight and level, at an airspeed of about 75 mph, when the pitch control became erratic. The pilot stated that the control stick started "slamming" fore and aft to the limits, the airplane nose began pitching up and down, and the airplane began buffeting "like it was going to come apart." The pilot declared an emergency and reduced airspeed to 50 to 60 mph, which slightly lessened the fore-and-aft stick movement and pitch but did not control it. The pilot turned to clear steep terrain and chose a field for an emergency landing. He was able to make final directional corrections and flew the airplane to landing about 40 to 45 mph and 200 to 300 ft per minute rate of descent. The left wing and horizontal stabilizer struck the ground. Examination of the airplane revealed a broken right elevator control rod; the left elevator control rod was not broken and moved normally. The broken control rod was a factory-supplied, 1/2-inch aluminum tube with bearings at each end. The attach points of the control rods appeared to be intact, the bearings were still connected and safety wired, and all other control rod linkages were connected. Further examination revealed no indication of any preexisting failure on the fracture surface of the right elevator control rod. The deformation of the rod was indicative of a bending failure. The pilot reported after the accident that he may have encountered flutter, but it could not be determined when or if that occurred.

Verbatim NTSB analysis and probable cause from the NTSB dataset