Aircraft Accident/Incident Report

Crestview, Florida 32536
Saturday, July 15, 2006 12:45 CDT

The pilot stated to the responding FAA inspector that during cruise flight the engine made a loud bang with a subsequent loss of engine power. The propeller remained windmilling and there was no response to engine controls and a restart. The pilot declared an emergency and elected to land in an open area within a timberland. The approach was normal until the landing. The main wheels touch down first and the nose wheel followed, which dug into the terrain, separating, and the airplane flipped over before coming to a stop. The pilot and passenger exited the airplane unassisted. Post recovery examination revolved there was a lost of continuity in the engine. The engine was taken to the manufacturer for a teardown examination. The crankshaft was separated at the No. 2 main bearing. The crankshaft and crankcase halves alone with associated parts were examined at the NTSB Materials Laboratory in Washington, D.C. The crankshaft was fractured through the aft cheek of the No. 2 main bearing journal. Optical examinations found features typical of fatigue propagation, smoothly textured surfaces with curved arrest lines, on the forward facture. Ratchets marks indicated that the fatigue initiated at multiple locations on the surface of the aft radius of the main journal surface with rearward propagation through the crank cheek. The fatigue initiation was located at the approximate tangent point between the aft journal radius and the face of the forward face of the cheek. The surface of the No. 2 main journal was circumferentially roughened but not deeply gouged. Heat tinting darkened was observed in the local areas. Other main and cylinder journals showed some local damage but none to the extent of the No. 2 main. The main bearing shells for the No. 2 main were fractured and broken up into several pieces. Many were not accounted for. The other bearing shells were intact showing various levels of wear, damage and debris embedment. The bearing shells were marked as FAA-PMA part numbers SA642720M10, indicating 0.010 inch oversize bearings. Engine logbooks reflect, the engine last received a major overhaul on April 22, 1998, 1,354 flight hours before the accident. On August 27, 2004, 315 flight hours before the accident; all six cylinders were replaced with new cylinders. On September 5, 2005, 141 flight hours before the accident, the airplane had an annual inspection. On July 8, 2006, about three hours before the accident, the engine had maintenance done to its turbocharger.

Spinning of the crankshaft No. 2 main bearing for undetermined reasons resulting in damage to the aft cheek of the No. 2 main bearing journal and fatigue failure of the crankshaft.