CEN13LA256

The pilot performed aerobatic maneuvers for about 5 minutes near a friend's farm and then departed the area. About a minute later, the airplane reappeared and began a left bank that became a spiral descent until ground impact. An examination of the airplane revealed no preimpact anomalies that would have precluded normal operation. The autopsy revealed that the pilot had severe coronary artery stenosis in the proximal left anterior descending coronary artery. According to the pilot's wife, although he had symptoms that may have been related to this disease, he had not received medical attention for them, so the disease was undiagnosed. She added that he had experienced dizziness while previously flying aerobatic maneuvers. In addition, both the pilot's father and grandfather experienced premature sudden cardiac death, which doubled the his risk of having sudden cardiac death. The autopsy was unable to determine whether an acute cardiac event occurred at the time of the accident. However, based on the pilot's recent medical symptoms, severe fixed coronary artery stenosis, and family history of sudden cardiac death and the additional physiologic stress of performing aerobatics, it is likely that the pilot became incapacitated due to an acute cardiac event and lost control of the airplane.

The accident airplane was issued its initial experimental, amateur-built certificate by the Federal Aviation Administration (FAA) on June 20, 1974. On April 20, 1981, the airplane was issued an experimental, amateur-built special airworthiness certificate with an indefinite expiration. The airplane had a total time of 1,295 hours and 1,277 hours as of the date of the last annual inspection, which was completed on April 20, 2012. The airplane was equipped with a Lycoming O-360-C1A engine having serial number L-1156-36. As of the last annual inspection, the engine had accumulated a total of 2,194 hours, with 366 hours since last major overhaul. On May 5, 2013, about 1930 central daylight time, a Eskildsen Steen Skybolt airplane, N7KE, was substantially damaged during ground impact near Easton, Minnesota. The pilot was fatally injured. The airplane was registered to Construction Engineering Services, LLC and was operating under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and a flight plan was not filed. The flight departed from Mankato Regional Airport (MKT), Mankato, Minnesota at an unknown time. Witnesses observed the airplane executing aerobatic maneuvers and then roll to wings level as it proceeded to the north. About 30 to 60 seconds later, the airplane reappeared flying southbound. The witnesses heard an engine noise similar to a backfire as well as a reduction in power, followed by the airplane initiating a descent and a turn to the left. The airplane continued in a left turning, spiral descent until ground impact. The pilot received his first medical certificate in 1988. Over the ensuring years he underwent several orthopedic surgical procedures but did not report any ongoing medical problems or medication use. On his last medical certificate issued, his height was 74 inches and his weight was 237 pounds (body mass index = 30.4). His blood pressure was 124/84 and his heart rate was 68. On May 5, 2013, an autopsy was performed on the pilot at the Ramsey County Medical Examiner's Office. The medical examiner determined the cause of death to be multiple traumatic injuries. In addition, significant natural disease was identified on autopsy. Evaluation of the coronary arteries identified an area of approximately 80% stenosis in the proximal left anterior descending artery. No other evidence of significant disease was found. Cardiac histology was reported as "normal" by the pathologist. The FAA's Civil Aeromedical Institute in Oklahoma City, Oklahoma, performed toxicology testing on the pilot. The test was negative for carbon monoxide, ethanol, and tested drugs. Based on conversations with family, over the six months prior to the accident, the pilot had at least one episode of chest discomfort and palpitations, some heartburn, and at least one episode of dizziness while performing aerobatics. In addition, both the grandfather and father of the pilot had suffered suddencardiac death; the father at age 42 and the grandfather at age 52. The pilot held a third class aviation medical certificate, which does not require an EKG. His wife stated that the pilot had never undergone cardiac related tests (ie. EKG, stress). The pilot, age 44, held a private pilot license with single-engine land and instrument ratings. On May 8, 2012, the pilot was issued a Class 3 medical certificate with no restrictions. No significant issues were identified by the pilot or aviation medical examiner during this or previous examinations. The pilot had accumulated a total of 725 flight hours, with 63 hours flown in the last 90 days. The airplane came to rest in a level, plowed field, with no evidence of a post impact fire. There were no ground scars leading to the accident site. Both left and right bi-wings sustained substantial damage during ground impact. FAA personnel confirmed flight control continuity at the accident site. The engine was examined at a salvage location by representatives of Lycoming Engines and the FAA. Both propeller blades were bent aft slightly at about mid span. The sparkplugs exhibited normal wear when compared to the Champion Aviation Check a Plug Chart AV-27. The crankshaft was rotated by hand and thumb compression was established on all cylinders. Drive train continuity was established throughout the engine. The cylinders were borescope inspected and no anomalies were noted. Both magnetos had no visual damaged and both produced spark at all the leads. The impulse couple on the left magneto was weak and not engaging consistently. The oil pickup screen was found free of debris. Examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.