What happened
On May 31, 2020, an experimental Cub Crafters CCK-1865, registration N303KP, was involved in an accident near Valley Center, California. The flight was being operated under Part 91 for personal use. The pilot had previously completed four short flights that day and was performing a fifth flight to take a passenger over a residence.
The aircraft departed from Lake Wohlford Resort Airport in Escondido at approximately 17:35. After maneuvering near a building, the airplane began circling the accident site at altitudes between 100 and 300 feet above ground level. During this period, the airspeed fluctuated between 40 and 50 knots.
At approximately 17:57, the aircraft entered a left turn with a bank angle exceeding 40 degrees. Witness video captured the airplane pitching up into a nose-high attitude, followed by a left wing drop and a nose-low descent. The aircraft impacted the ground shortly after. The accident resulted in 1 fatal injury to the pilot and 1 serious injury to the passenger.
The investigation
Engine analysis via sound spectrum revealed the engine was operating at the recommended speed of 1,800 to 2,000 rpm at 1,850 feet MSL. Engine monitor data showed that cylinder head temperatures and exhaust gas temperatures remained within normal ranges until the end of the recorded data. The final data point indicated an airspeed of 28 knots and a vertical speed descending at more than 300 feet per minute.
FAA inspectors confirmed that flight control continuity was maintained. Calculations based on the manufacturer's power-off stall speed data indicated that the airplane's airspeed had dropped below the stall margin during the final turn.