The private pilot was intending to conduct a cross-country flight when the light sport airplane collided with a power line and terrain. Several witnesses reported seeing the airplane flying at low altitude near the accident site. There were no eyewitnesses to the final portion of the flight; however, an individual near the accident site heard the airplane's engine from inside his residence. After the crash, he saw the airplane in the field outside his residence and flames from the power lines along the road. A postaccident airframe examination and operational engine test revealed no evidence of a mechanical malfunction or failure that would have precluded normal operation.The intended destination was 65 miles north-northwest of the departure airport. The accident site was located about 12 miles northwest of the departure airport, and according to engine data, the airplane crashed about 35 minutes after takeoff. The wreckage debris path was consistent with the airplane colliding with a 35-ft-tall power line while on a southerly heading. The pilot's partner reported that the pilot was familiar with the route of flight and that he had made the flight numerous times. She further noted that he typically flew at 3,500 ft mean sea level (msl) during cruise flight. A review of available air traffic control (ATC) radar data revealed no transponder or primary radar data associated with the flight. The lower limit of ATC radar coverage in the general area of the accident site was about 2,000 ft above ground level (2,750 ft msl). Based on the crash location, witness accounts, and the lack of ATC radar data for any portion of the flight, the pilot did not follow a direct route toward his intended destination or climb to his normal cruise altitude.According to toxicological test results, the pilot was using two impairing medications, diphenhydramine and gabapentin, which likely impaired him during the flight. However, he had likely used these drugs during previous flights where he did not demonstrate unusual behavior; thus, these medications alone do not explain the pilot's performance during the accident flight. The pilot remained at low altitude and in the general vicinity of the departure airport; he did not fly toward his intended destination, which suggests that he may have become confused about where he was, what he was doing, and where he was going.Page 2 of 11 CEN18FA060The pilot had several medical conditions that could have affected him during the flight; coronary artery disease, multiple previous ischemic and hemorrhagic strokes, and recent pneumonia. Another stroke or transient ischemic attack (TIA) during the flight could have made him confused or made it difficult to operate the airplane due to weakness in his arm and/or leg. The pilot's coronary artery disease and valvular heart disease could have also caused weakness and confusion due to low blood pressure as a result of an arrythmia, or an ischemia could have worsened his shortness of breath and caused him to become hypoxic (have low oxygen), which could also result in confusion. Any such physiologic event would have further worsened the psychoactive effects from the two sedating medications the pilot was using. Although the pilot was likely impaired by his use of two impairing medications, by themselves they do not explain the airplane's flight path and his behavior. Therefore, it is more likely that some physiologic event occurred that caused his inability to safely carry out the flight.