Planemasters

The pilot was conducting a Part 135 on-demand cargo flight in instrument meteorological conditions. After executing a second missed approach, he informed air traffic control (ATC) of his intentions to divert to an airport located about 36 miles to the southeast. About 7 minutes after executing the second missed approach, the pilot began making unintelligible radio communications that ATC characterized as very garbled and difficult to understand, “almost hypoxic.” ATC then instructed the pilot to utilize oxygen. About 19 minutes after the second missed approach, ATC informed the pilot that the airplane had descended 1,600 ft, not following assigned course vectors or instructions and asked if everything was alright, to which no response was received. After attempting to relay communications through other airplanes in the area, an unintelligible response was received from the accident airplane. ATC then made numerous transmissions to the accident pilot urging him to utilize oxygen and open a window. No further communications were received from the accident airplane. A witness reported that he saw the airplane descend out of a low overcast cloud layer at a high rate of descent. The airplane then abruptly transitioned into a steep climb before re-entering the clouds. A few seconds later, he heard the airplane impact terrain and responded to the accident site. The sudden change in communications from the pilot indicates a possible impairment. When combined with the ATC data, the witness account, and the lack of any mechanical irregularities or malfunctions with the airplane, it is likely the pilot experienced difficulty controlling the airplane due to impairment. While the pilot was at an increased risk for an acute cardiovascular event, the extremely limited available medical evidence leaves no way to quantify that risk and no evidence regarding whether such an event occurred. As a result, whether the pilot was incapacitated by an acute medical event cannot be determined from the available medical information.

The airplane collided with trees and terrain following a loss of control during an Instrument Landing System (ILS) approach at night. The impact occurred approximately 2.1 miles from the approach end of the runway. A witness reported hearing the airplane at "mid-throttle" as it flew over. He then heard the power increase followed by the impact. The witness stated there was no precipitation at the time of the accident and there were "severe winds, mostly from the south, shifting volatile directly from the east." He also stated the visibility was "extremely poor." Statements were received from five pilots who landed in transport category airplanes around the time of the accident. Three of these pilots reported experiencing a crosswind that varied from 15 to 50 knots during the approach. Four of the pilots reported airspeed fluctuations that varied between +/- 8 knots to +/- 10 knots during the approach. Three of the pilots reported breaking out of the clouds between 200 and 300 feet agl. Radar data indicates the airplane was high on the glideslope until it entered a rapid descent from an altitude of about 2,300 feet. Examination of the airframe, engine, and propeller governors failed to reveal any failures/malfunctions that would have resulted in the loss of control.

Departed Marion without a weather briefing. Pilot advised during approach that last person making approach reported moderate to severe turbulence on final. Subsequently cleared to land and given wind 360 at 30 gusting 40. Also advised that another aircraft reported a 20 knots windshear on final. The pilot reported that when he had descended to 1,500 feet msl, the aircraft encountered strong turbulence and the airspeed went from stall to redline. Despite adjustment to flaps and throttle, the airplane was uncontrollable.