Diamond DA 40 N361DS

Air traffic control radar data showed the airplane making multiple circles with altitude variations ranging from 8,400 feet mean sea level (msl) to 700 feet msl. A witness reported that he heard a single-engine airplane flying overhead and that he heard the engine changing pitch, which made him immediately look up. He saw what appeared to be a single-engine airplane doing “loops” near his house. He was able to see the silhouette of the airplane and the two white strobes under its wing tips. The engine pitch dropped as the airplane was climbing. About 3 seconds, later the witness could see the red and green lights on the airplane’s wing tips, as well as the strobes again as the engine pitch increased. He observed the airplane as it made “a couple more loops.” The airplane appeared to level out and continue flying west-northwest and, about 1 minute later, it made a turn toward the north. The airplane was located the following day in a wooded area about 5 miles from the witness’s home. Night visual meteorological conditions prevailed and the airplane was flying over sparsely lighted terrain at the time of the accident. The crash debris field indicated that the airplane was in a shallow, controlled descent at impact. Examination of the wreckage revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation. Based on the available information, it is likely that the pilot experienced spatial disorientation before impacting the ground. Although toxicological testing of the pilot’s blood specimens showed potentially lethal carbon monoxide levels, the testing also showed very low hemoglobin concentration, which suggests significant contamination (possibly during postaccident firefighting activities) that made the sample unsuitable for accurate testing. Examination of the airplane’s debris path found evidence to preclude any possibility that the pilot inhaled carbon monoxide during the postcrash fire, and examination of the airplane revealed no evidence of any precrash leaks in the exhaust system. Further, the pilot demonstrated the ability to talk coherently to air traffic controllers about 1 hour before the accident and to operate and maneuver the airplane during the flight. Given the absence of any detectable exhaust leak in the airplane, the uncertain quality of the specimen used for toxicological testing, the lack of confirmatory testing, and the pilot’s demonstrated abilities during the flight, it is unlikely that the pilot experienced any significant premortem exposure to carbon monoxide. Ethanol was detected in multiple tissues of the pilot, and the levels suggest that there was some degree of postmortem ethanol formation, although the levels also suggest that some of the alcohol present was from ingestion; however, the contamination of the pilot’s blood specimens raises the possibility that the detected ethanol levels are misleading as well. Thus, it is not possible to determine if the pilot was impaired at the time of the accident.

Quoted verbatim from the NTSB record.