ERA14FA403 · Beech S35

A friend of the commercial pilot reported that the purpose of the personal flight was to relocate the airplane to an airport about 19 miles northeast of the departure airport, where it could be stored in a hangar while the pilot was on an extended trip overseas. He added that the pilot attempted to complete the flight the day before the accident but that he was unable to start the airplane because the battery required servicing; the battery was serviced the morning of the accident.

A lineman reported that, before the airplane departed on the day of the accident, he observed the pilot perform an extended engine run-up. He stated that typically the pilot would just "hop in and go." Radar data showed the airplane just after departure on a northerly heading climbing to about 1,600 ft mean sea level (msl). About 2 minutes after departure, the airplane turned west and descended to about 900 ft msl as it turned 360 degrees near the pilot's home. The airplane then resumed a northeasterly course and climbed to 2,400 ft msl, presumably toward the destination airport. About 9 minutes after departure, the airplane entered a descending right turn. The final radar targets showed the airplane about 1.25 nautical miles southeast of the accident site about 1,400 ft msl and on an approximate magnetic heading of 285 degrees. Postaccident examination of the airframe and flight controls revealed no anomalies.

The propeller displayed signatures consistent with lack of engine power at the time of impact. Initial examination of the engine case revealed that it was breached in two locations, near the Nos. 2 and 4 cylinders, and that the Nos. 2, 3, and 4 connecting rods were fractured. Further examination of the engine revealed signatures consistent with preignition and/or detonation in the No. 6 cylinder, which had eroded the No. 6 cylinder piston face and subsequently allowed combustion gases to pressurize the engine crankcase. This likely caused the expulsion of oil from the engine via the breather tube and resulted in a lack of lubrication throughout the engine, consistent with the extreme thermal discoloration and mechanical damage observed in the engine's internal components. The cause of the preignition and/or detonation could not be determined.

During the approximate 10-minute flight before the engine lost power, the pilot should have received several indications of an engine anomaly, including, but not limited to, a drop in oil pressure, a rise in oil temperature, a rise in cylinder head temperature, and engine roughness. However, the airplane's flight track after takeoff, including the low-level circling of the pilot's home and its continuation to the destination airport rather than returning to the departure airport, suggests that the pilot either did not observe these signs nor recognize them to be indicative of a serious engine problem or that he thought he would be able to complete the remaining short flight to the destination airport. Although it is uncertain when the anomalous engine indications might have begun, given the pilot's extended engine run-up, it is possible that they were observable as early as before takeoff. The fact that the pilot had attempted to complete the flight the previous day and had been unable to do so would likely have increased the pilot's desire to reach the destination airport and contributed to his unwillingness to cancel the flight, return to the departure airport, or conduct a precautionary off-airport landing before the engine failed.

Although toxicological testing of the pilot's specimens detected pheniramine, diphenhydramine, and zolpidem, all of which can be sedating, the detected drug levels were well below therapeutic levels; therefore, it is unlikely that any of the medications or the combination of the medications impaired the pilot's ability to safely operate the airplane.

Verbatim NTSB analysis and probable cause from the NTSB dataset