Raytheon Aircraft Company A36 N566C accident near Greenville, North Carolina

Probable cause

The pilot’s loss of airplane control shortly after climbing into instrument meteorological conditions due to spatial disorientation (somatogyral illusion).

NTSB analysis

The instrument-rated private pilot and passenger were departing on an instrument flight rules (IFR) flight. The weather conditions that preceded and persisted until the time of the takeoff consisted of low ceilings (300 ft), mist, and fog with instrument meteorological conditions (IMC) through most of the area. After departure, the pilot flew the runway heading and climbed briefly before turning right and descending to about 200 ft. The right turn then stopped and the airplane flew a relatively straight ground track and resumed the climb. While flying at an altitude of about 600 ft, with the airplane climbing at a vertical speed of about 1,800 feet per minute, the airplane continued for about a mile before entering another turn to the right. The airplane stopped climbing during this turn after it reached a peak altitude of 1,000 ft. Shortly after, the right turn progressively tightened as the airplane began a descending spiral. A witness observed the airplane rolling as it descended out of the clouds before impacting terrain.

The airplane impacted the terrain at high-speed in a nearly 50° nose down, and steep right wing low attitude. Postaccident examination of the wreckage was limited by the level of impact-related damage and significant fragmentation. Within the wreckage that was examined, there was no indication of a preimpact mechanical malfunction or failure that would have precluded normal operation of the airframe or engine. Additionally, witness statements and impact signatures observed on the airplane’s propeller blades were consistent with the engine producing power at impact.

The instrument-rated pilot had completed an instrument proficiency check about 2 months before the accident. Since then, he had accumulated additional experience that included flight in simulated and actual instrument meteorological conditions, and had conducted several instrument approaches, all in the accident airplane. While his flight logs suggested that he had some familiarity operating the airplane and its newly installed electronic flight instrumentation under instrument flight rules, the pilot’s overall level of proficiency could not be determined from available information. The airplane’s erratic flight track on the accident flight, which included arrested climbs, descents, and low altitude turns that culminated in a tightening turn and high-speed descent was indicative of the known effects of spatial disorientation, specifically the somatogyral illusion (graveyard spiral). During the initial climb, once the pilot entered the clouds and lost all outside visual cues, it would have been difficult to recognize and respond to spatial disorientation unless he was confident and assertive in his use of the airplane’s avionics package and flight instrumentation.

The aortic plaque observed a postaccident autopsy of the pilot indicated some increased risk of an impairing or incapacitating cardiovascular event, although the magnitude of this risk was uncertain from the limited autopsy evidence. The limited qualitative toxicology results in tissue indicated that the pilot had used the sedating antihistamine medication diphenhydramine, but did not indicate the precise timing of his last use or whether he was experiencing associated impairing effects at the time of the accident. While the pilot had defective color vision, he had been approved for flight and there was no evidence to suggest that color vision played a role in the accident.

Text from the NTSB. Open the NTSB docket for ERA25FA143 for the full record.