ERA11FA299 · Piper PA-22-150

According to several witnesses, the airplane was in cruise flight at "high" altitude when the wings rocked and the airplane entered an uncontrolled descent. The airplane "spun a long time" and the engine sound was described as surging during the descent. The pilot regained airplane control, leveled briefly, the sound of the engine became smooth and continuous, and the airplane climbed. Soon after, the wings rocked again; the airplane departed controlled flight, descended behind trees and terrain, and the sounds of impact were heard. A review of the pilot’s records and employment history revealed demonstrated abilities in many different types of airplanes, in all types of environments and weather conditions. An examination of the maintenance records and the wreckage revealed a properly restored and maintained airplane, with no preimpact mechanical malfunctions or failures noted that would have precluded normal operation. Interviews and the pilot’s medical records revealed he had a history of diabetes, and diabetes-related health issues that included neuropathy (numbness) of the feet. Review of the pilot’s medical records revealed that his diabetes was controlled by medication and diet and that he was eligible for a Federal Aviation Administration medical certificate. A review of the autopsy and toxicology reports revealed no obvious medical event suffered by the pilot before the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset