Beech A36 N69286 accident near Shoreham, New York

Probable cause

A fatigue crack of the crankshaft at the No. 4 main bearing journal.

NTSB analysis

While the private pilot was conducting a cross-country flight, the airplane's engine started running roughly when the airplane was about 5,500 ft. The pilot pushed the mixture, propeller, and throttle controls to the full forward position, but the engine continued to run roughly. The pilot then decided to return to the departure airport. During the turn back to the airport, oil covered the windscreen. The pilot declared an emergency and asked air traffic control for radar vectors to a closer airport. The pilot was having trouble controlling the airplane, so he asked for vectors to another airport. Seconds later, he saw parts, which he thought were from the propeller, separate from the airplane. The engine then lost total power, and the pilot ditched the airplane into the water below. Postaccident examination of the engine revealed that the crankshaft was fatigue fractured at the No. 4 main bearing journal. The origin surface area of the fatigue crack was obliterated due to relative movement between the mating fracture faces; thus, the investigation could not determine the cause of the fatigue crack.

Text from the NTSB. Open the NTSB docket for ERA17LA069 for the full record.