WPR11FA090 · Beech S35

The 76-year-old private pilot departed during the hours of darkness on a return trip to his home airport. Radar data revealed a flight track consistent with the pilot hand flying the airplane without the assistance of an autopilot at altitudes appropriate for the terrain elevation. No radar data was available for the approach segments and accident sequence of the flight. Based on witness reports, the airplane appeared to perform a normal crosswind approach over a town and toward the airport runway. During the airport approach, the pilot made a normal radio call and did not appear to be in distress. As the airplane rounded the turn from crosswind to downwind, it continued in a shallow, high-speed descent, directly into the frozen surface of a lake adjacent to the runway.

The debris field was on a heading which approximated the downwind segment of the landing runway. The debris field length was consistent with a high-speed, right-wing-low, gradual descent into the ground. The landing gear and flaps were not in the landing configuration, and the speed brakes were not deployed. All sections of the airplane were located at the accident site, and no anomalies were noted with the airframe or engine that would have precluded normal operation. The damage to the propeller was consistent with the engine producing power at the time of impact.

The airport was located on the outskirts of a town, adjacent to a lake and a sparsely populated national park. The moon, which exhibited a 6 percent visible disk, would have provided limited illumination and would have been located low on the horizon and behind the airplane during the crosswind and downwind turns. The pilot's forward view would also have been dominated by a dark void as the airplane passed over the town, and began the landing approach. The pilot did not possess an instrument rating, which, coupled with the lighting conditions, could have made him vulnerable to spatial disorientation. Additionally, the airplane's impact trajectory was consistent with him encountering this phenomena.

The pilot had experienced a mild heart attack 6 years prior to the accident, with placement of stents in two coronary arteries, and a diagnosis of diabetes. He had denied any medical history in applications for FAA medical certificates. It was not possible to conclusively determine what role, if any, the pilot’s unreported medical conditions played in the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset