On June 21, 2018, about 1527 mountain daylight time, a Schempp-Hirth Arcus M motorglider, N16DN, was destroyed when it was involved in an accident near Richfield, Utah. The pilot and passenger sustained minor injuries. The glider was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The pilot was participating in a soaring competition and stated that it was a "very good soaring day." The pilot reported that he was "climbing stably" in thermal lift approaching about 17,000 feet mean sea level (msl) when one of the rudder pedals "slammed back" and threw his foot off the pedal, accompanied by a "thud" sound. He could not recall which direction the rudder pedals moved and added that, when this occurred, there was no change in the glider's yaw, pitch, or bank angle; however, he was unable to move the rudder pedals. Shortly thereafter, the glider's bank angle and speed began to increase, and the pilot thought that the glider had entered a spin or spiral dive. The pilot applied corrective flight control inputs, but was unable to recover, and instructed the passenger to bail out. The pilot stated that as he jettisoned the canopy, "the wing broke" and he and his egressed.
The wreckage debris field was located within mountainous terrain about 7 miles southeast of Richfield. The wings separated from the glider during the accident sequence and were located about one mile from the main wreckage, which comprised the empennage and a portion of the fuselage. The vertical stabilizer was laying on its right side, the right horizontal stabilizer was folded under the vertical stabilizer, the damaged rudder was partially attached, and the elevators were adjacent to the horizontal stabilizer. The wreckage was recovered to a secure location for further examination.
Examination of the recovered wreckage revealed that the upper three inches of the rudder were separated. The left and right elevators were not identified within the recovered wreckage. The empennage was fractured from the fuselage just forward of the vertical stabilizer but remained attached by the control rods and cables. The vertical stabilizer was fractured near the mid-span point with a corresponding fracture of the rudder. The horizontal stabilizer remained attached to the top of the vertical stabilizer and was engaged with the forward and aft mount points. The elevator hinges on the horizontal stabilizer were all intact and undamaged.
The elevator aft fuselage forward control rod was fractured in three places and the remaining elevator control system was intact. There were several areas of damage and deformation of the elevator flight controls adjacent to areas of fuselage damage. The elevator trim locking control rod was near the aft most position.
The aileron controls were fractured and deformed in multiple places between the forward control stick and the tunnels, consistent with the extensive forward fuselage damage; however, all the components were present with the exception of a portion of the outboard aileron control rod, which was not located within the recovered wreckage. The fractures all had a dull, grainy appearance consistent with overstress separation.
The forward and aft rudder pedal assemblies were deformed and fractured into multiple places. The left and right forward and aft rudder cables remained attached to their respective anchor points; however, the anchor points were fractured from the fuselage. The right rudder cables were intact from the pedals to the rudder control horn. The left forward pedal rudder cable was fractured near the pedal with a splayed, broomstraw appearance consistent with tension overload. The left rudder cables were otherwise intact from the pedals to the rudder control horn. The rudder stops at the rudder control horn each had evidence of a single impact.
The upper rudder hinge pin assembly on the vertical stabilizer was fractured and deformed upward. The upper rudder hinge bearing was fractured from its mounting plate on the rudder. There was corresponding damage to the lower portion of the upper rudder hinge cutout. The rudder control horn was intact and attached to the rudder. For additional information, refer to the Airworthiness Group Chairman's Factual Report located in the public docket for this accident.