Amateur-built ZODIAC 601XL N929GB accident near Thompson'S Station, Tennessee

Probable cause

The sport pilot's decision to depart in and continue flight in instrument meteorological conditions, which resulted in controlled flight into terrain.

NTSB analysis

The sport pilot was picking up his airplane following maintenance and intended to return the airplane to its base 57 nautical miles away. The owner of the maintenance facility cautioned the pilot about the weather along the route of flight and stated that the conditions at the departure airport included overcast clouds at 400 ft above ground level (agl). The pilot replied that the weather was improving and that he was familiar with the area. There was no record of the pilot having obtained a weather briefing prior to departure. The maintenance facility owner watched as the pilot subsequently took off from a taxiway and made a steep left banking turn to depart on course to his destination. About 25 minutes after departure, a witness saw the airplane flying between 150 and 200 ft agl with the engine running at a high-power setting.The airplane impacted trees and terrain about 34 nautical miles from the departure airport and oriented toward the departure airport. A nearby resident stated that the weather in the area at the time of the accident included low clouds about treetop level with very limited visibility. Review of reported weather conditions from nearby airports about the time of the accident revealed cloud ceilings ranging between 400 ft and 1,400 ft agl.

Examination of the airplane and engine revealed no mechanical anomalies that would have precluded normal operation. The pilot's decision to depart and continue flight in instrument meteorological conditions resulted in controlled flight into terrain. As the airplane impacted a stand of trees in a wings-level attitude prior to impact with the ground, this supports the position of controlled flight into terrain rather than that of spatial disorientation.

Autopsy of the pilot revealed evidence of severe cardiovascular disease with an implanted defibrillator; however, interrogation of the pacemaker revealed no anomalies and it is unlikely that the pilot's cardiovascular disease contributed to the accident. Toxicology testing revealed that the pilot had used a potentially impairing medication, clonazepam, at some time before the accident; however, the blood level was well below the therapeutic and impairing level and therefore did not affect the pilot's decision-making or directly contribute to the accident.

The pilot's physician documented a caregiver's concerns for the pilot's impulsive behavior and difficulty remembering where he was while driving. The pilot's actions and decision to attempt to fly his airplane in poor weather conditions that exceeded his skill and ability are consistent with the reported impulsive behavior. Review of the pilot's medical history was unable to determine whether the pilot's baseline history of poor decision-making and airmanship as assessed by a previous flight instructor was solely responsible for the circumstances leading up to the accident, or the assessment of his impulsive decision-making by undiagnosed neuropsychiatric deficit, contributed to the circumstances of this accident.

Text from the NTSB. Open the NTSB docket for WPR18FA053 for the full record.