This March 2010 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Lancair IV-P. Injuries: 1 Fatal. Location: Hilton Head, S.C. Aircraft damage: Substantial.
What reportedly happened: According to the pilot, the airplane was in cruise flight when the instrument panel begin to vibrate heavily and oil begin to cover the wind screen. There was a loud “bang” from the engine and then the engine then lost power. The pilot had no forward visibility because of the oil on the windscreen and could not maintain altitude. He elected to make an emergency landing on a nearby beach. During the landing the plane struck and killed a pedestrian.
Examination of the airplane revealed that the propeller assembly separated from the crankshaft and was missing. The propeller assembly and propeller flange were not recovered. An examination by the NTSB Materials Laboratory of the crankshaft revealed that the aft face of the fracture contained crack arrest marks. The fracture of the crankshaft was caused by multiple-origin fatigue cracks that emanated at the aft relief radius for the propeller flange. The records for the engine and airplane did not show an entry of a propeller strike. However, multiple-origin fatigue cracks that extend nearly 50% around the circumference of the aft relief radius for the propeller flange suggest that the propeller had struck an object prior to fracture of the crankshaft. In the absence of material anomalies, the fatigue cracking appears likely to have been caused by external impact stress, such as a propeller strike.
Probable cause: A loss of engine power due to the failure of the crankshaft as a result of a previously undocumented propeller strike.
For more information: NTSB.gov. NTSB Identification: ERA10LA175
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