On June 4, 2017, about 0824 mountain daylight time, an Excaliber experimental light sport airplane, N78DZ, was substantially damaged when it impacted terrain near Albuquerque, New Mexico, during an emergency landing due to flight control anomalies. The commercial pilot was not injured. Visual meteorological conditions prevailed throughout the area and a flight plan was not filed. The airplane was registered to the pilot and the personal flight was being conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The local flight originated at 0715 from the Double Eagle Airport (AEG), Albuquerque, New Mexico, and was enroute back to AEG when the accident occurred. According to the pilot, he had been flying a little over an hour without any problems since takeoff from AEG. He was flying straight and level, about 75 mph (below never-exceed speed), when the pitch control became erratic. 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 choose a relatively flat 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 airplane remained upright, but the nose gear and the left main gear sheared off, the airplane turned 180°, and the left wing and horizontal stabilizer struck the ground. Examination of the aircraft by a Federal Aviation Administration inspector and the pilot after the accident revealed a broken, right elevator control rod. The left elevator control rod was not broken. The control rod that separated 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 and attach points were connected. There was normal movement of the left elevator control system (rod still intact). The damaged control rod (right elevator) and the intact control rod (left elevator) were compared and examined by a National Transportation Safety Board structures engineer. According to the engineer, there was no indication of any pre-existing failure on the fracture surface of the right elevator control rod. The deformation of the rod was indicative of a bending failure of the rod. The pilot reported after the accident that he may have encountered flutter.