What happened
On September 5, 2017, an experimental Cobalt Co50 Valkyrie, registration N523CA, performed a hard landing at Castle Airport in Atwater, California. The flight was being conducted under Part 91 regulations as a test flight for Cobalt Aircraft Industries, Inc. to evaluate handling qualities at specific configurations. The flight originated from Atwater at approximately 1405 PDT, and the accident occurred at about 1430 PDT under visual meteorological conditions.
Prior to the accident, the pilot conducted two test runs to check rotation performance. During these attempts, the aircraft failed to rotate despite full aft back pressure. Following this, the ground crew adjusted the ground trim by 2 degrees, bringing the total to 10 degrees. The pilot then prepared for a departure from runway 3 and planned for a rotation speed of 75 knots.
After rotating, the pilot encountered extreme difficulty controlling the aircraft at approximately 50 feet above ground level. While the aircraft eventually climbed to 1,400 feet, the pilot noted that the ailerons were ineffective, though directional control was maintained via the rudder. The aircraft also exhibited sporadic pitch stability. After approximately 20 minutes of flight, the pilot stabilized the aircraft at 90 knots and attempted to land using steady thrust and rudder control. During the landing flare, approximately 10 feet above the runway, the aircraft experienced a loss of lift and struck the surface hard. The impact caused the right landing-gear leg to separate and resulted in damage to the right-wing spar. The pilot was not injured.
The investigation
A company representative reviewed onboard recorders and video footage. The recordings indicated that the aircraft experienced a loss of roll control following a rotation speed that was faster than expected, occurring between 80 and 85 knots. The investigation noted that for this specific test flight, the aircraft was at an increased weight and the winglet position had been changed, which contributed to the loss of aileron effectiveness.