NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The airline transport pilot was conducting a local personal flight in the experimental amateur built airplane, with one passenger on board. Several witnesses located near the accident site reported that they heard the airplane's engine and that it sounded like it was making power changes. The witnesses added that they then saw airplane debris floating in the air. One witness stated that the engine was running during the entire descent and that he saw the airplane spiraling and descending in a cork-screw type maneuver. Another witness reported seeing the airplane inverted at a low altitude just before impact.
Postaccident examination of the airplane revealed damage to the horizontal stabilizers and elevators that was consistent with a downward failure in positive overload. The loads required to fail the horizontal stabilizers and elevators cannot be generated from normal flight or control movements. Such failures would have required an abrupt pull back on the stick and corresponding movement of the elevator to a trailing-edge-up position, at speeds greater than the airplane's maneuvering speed. Failure of the horizontal tail first would have caused the airplane to pitch down rapidly, producing air loads on the upper surface of the wing that were sufficient to fail them in negative overload. The damage observed on the wings was consistent with a downward failure in negative overload. Additionally, there were no indications of any pre-existing cracks or anomalies with the horizontal stabilizers, elevators, or wing structures, and no pre-accident anomalies were observed that would have precluded normal control of the airplane.
A review of the weather information indicated that there were likely low-level winds gusting from 26 to 46 knots at the time of the accident and that moderate-to-severe turbulence likely existed at the accident site. The weather conditions likely contributed to the in-flight breakup by either aggravating a flight maneuver or preventing a recovery from a loss of airplane control.
Although doxylamine was detected in the pilot's liver it was not detected in the blood; therefore, it is unlikely that it was causing any performance decrements that would have affected the pilot at the time of the accident.