NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The accident occurred during the commercial pilot’s third flight of the day in the accident airplane. The pilot reported that he used the airplane’s heater throughout the day. The pilot reported having a headache and experiencing “butterflies” in his stomach during the end of first flight. The headache subsided after the flight, and he felt fine during the second flight, but the headache returned after he landed. Before the third flight, the pilot expedited his time on the ground because he was concerned about getting the engine started in the cold weather. The pilot started the engine and sat in the airplane while he filed his flight plan and got organized for the flight. The pilot added that, while taxiing to the runway, he still had the headache, and he experienced another episode of “butterflies.” He stated that the symptoms were more intense at that time than they had been in the morning but that they subsided by time he reached the runway, and he felt “good” but became “hyper focused.” He performed an engine run-up and repeated the takeoff checklist three or four times until the controller asked if he was ready to take off, which “snapped” him out of repeating the takeoff checklist. The pilot was in the airplane with the engine running for about 12 minutes before takeoff.The pilot remembered being cleared to a heading of 240° and setting the autopilot heading bug before taking off. He stated that, while climbing out, he experienced another case of the “butterflies.” He added that he began a turn and activated the autopilot during the turn. The last thing he remembered was being cleared to 6,000 ft on a heading of 240°. After the pilot attempted to check in twice with departure control (he was still on the tower control frequency), air traffic controllers repeatedly attempted to contact the pilot without success. Radar data showed that the airplane climbed higher than 12,000 ft and was off course. The airplane continued to fly until it ran out of fuel and crashed in an open field. The pilot was not conscious until after the airplane impacted the field. He stated he was very confused and had loud ringing in his ears at this point. The pilot freed his legs from the wreckage and exited the airplane. He stated he was very weak and had difficulty with his balance and ability to walk as he made his way to a nearby house.A postaccident examination revealed that the both fuel tanks were empty. The cabin heat was found on, and the cabin vent control was found off. The exhaust muffler had several cracks, one of which contained soot/exhaust deposits on the fractured surfaces, indicating it existed before impact. The crack would have allowed exhaust gases to enter the cockpit/cabin. The pilot reported that the airplane was not equipped with a carbon monoxide (CO) detector. A review of maintenance records showed that a new exhaust system was installed on the airplane on January 25, 2007, at a tachometer time of 2,343 hours. The last annual inspection was conducted on February 2, 2016, at a tachometer time of 2998.0 hours. The tachometer time at the time of the accident was 3,081 hours.The pilot’s CO level, when tested over 4 1/2 hours after the accident, was 13.8%. Given the half-life of CO in the blood stream over 4 to 5 hours while breathing ambient air, the pilot’s CO level at the time of the accident was at least 28% and likely significantly higher because oxygen was administered in varying amounts during the first few hours of his postaccident medical care. The pilot’s high CO level led to his incapacitation due to CO poisoning and the airplane’s continued flight until it ran out of fuel and impacted terrain.