What happened
On October 7, 2020, at approximately 0530 EDT, a Beech S35, registration N449CT, crashed near Knoxville, Tennessee, resulting in two serious injuries.
The pilot and passenger arrived at Knoxville Downtown Island Airport (DKX) early in the morning to prepare for a flight to Morristown, Tennessee. During taxi, the pilot noted that the airport's automated weather observation system (AWOS) reported a 200-foot ceiling, though the pilot believed he could see stars. However, the passenger recalled the morning being dark and foggy with no visible sky.
After performing standard engine and control checks, the pilot took off from runway 8. Shortly after takeoff, the aircraft impacted trees and vegetation at an altitude of approximately 10 feet, about 600 feet from the end of the runway. The airplane then struck an open field in a level attitude, sliding on its belly for 500 feet. The pilot later contacted 911 via telephone to report the crash.
The investigation
An examination of the engine and propeller showed no evidence of mechanical failure prior to the impact. The engine was at takeoff power at the time of the crash. The aircraft's engine data monitor showed the flight lasted approximately 5 minutes and 54 seconds without any recorded malfunctions.
Investigators found that the pilot had not contacted Flight Services for a formal weather briefing. While the pilot believed the weather was clear enough for visual flight, the AWOS had been reporting visibility of only 1/4 mile for at least 15 minutes prior to departure. The National Weather Service had also issued advisories for dense fog and low clouds several hours before the accident.
Findings
Investigators determined that the pilot experienced spatial disorientation during the takeoff phase. It is believed that during the transition from the well-lit runway into a dark sky, the pilot experienced a somatogravic illusion. This illusion likely caused the pilot to perceive a pitch-up sensation due to the aircraft's linear acceleration, leading him to push the nose down and causing the collision with terrain.