What happened
On May 29, 2021, a Cessna Citation CE-501, registration N66BK, departed Smyrna Airport (MQY) in Tennessee, bound for West Palm Beach, Florida. The flight was operating under instrument flight rules in weather conditions characterized by an overcast ceiling of 1,300 feet and mist.
Shortly after takeoff, the aircraft entered the clouds while performing a climbing right turn. Air traffic control (ATC) communications and radar data show that the pilot initially failed to respond to a heading instruction but later acknowledged a turn to a heading of 130 degrees. After the pilot acknowledged the instruction, the controller requested the aircraft climb and maintain 15,000 feet MSL, but the pilot did not respond to this subsequent instruction, and the controller was unable to re-establish communication.
Radar data indicated that the aircraft performed a series of heading changes, climbs, and descents before entering a steep, descending left turn. The final radar return showed the aircraft at approximately 700 feet MSL, descending at a rate of 31,000 feet per minute. The aircraft impacted Lake Percy Priest at a high rate of speed. The pilot, a pilot-rated passenger, and five passengers were 7 fatal.
The investigation
Investigators examined the recovered wreckage, which included both engines, the tail section, and portions of the wings. Post-accident engine examination found evidence of powered rotation at the time of impact and no evidence of mechanical malfunctions that would have prevented normal operation. Flight control cables exhibited fracture features consistent with overload separation due to the impact.
An airplane performance study using ADS-B data and a 6-DOF simulation determined that the aircraft's maneuvers were consistent with the onset of somatogravic illusion. The study suggested that during descents, the pilot likely perceived the aircraft as pitching up rather than down due to the accelerations experienced. This disorientation, combined with a high workload and limited visual cues in IMC, led to the unrecoverable descending left turn.
Toxicology testing detected low levels of ethanol in the muscle and kidney tissue of the pilot and the pilot-rated passenger. However, investigators determined that the identified ethanol likely originated from sources other than ingestion and did not contribute to the accident.