LAX97LA116

While in cruise flight the pilot felt a slight vibration and immediately made a power change without affect. After reducing the engine rpm from 2300 to 2100, the airplane vibrated hard for a split second and then smoothed out. At that point, the propeller had separated from the engine with part of the crankshaft. Metallurgical examination of the crankshaft revealed that the fatigue failure occurred inside the crankshaft bore 1.7 inches forward of the crankshaft oil seal. The point of origin was at two corrosion pits.

On March 2, 1997, about 1750 hours mountain standard time, a Beech J35, N39W, was substantially damaged during a forced landing at Morristown, Arizona. The pilot received minor injuries and the passenger received serious injuries. Visual meteorological conditions prevailed for the personal cross-country flight and no flight plan was filed.

The pilot reported that while in cruise flight he felt a vibration and immediately made a power change without affect. He further reduced the engine rpm from 2,300 to 2,100, the airplane vibrated hard for a split second and then smoothed out. At that point, the propeller separated from the engine with part of the crankshaft. The failure occurred over remote desert terrain and the propeller was not recovered.

Engine information

According to the engine logbook, the engine had been overhauled on April 11, 1989, at 1,819 total hours. At the time of the accident, the engine had accumulated about 937 hours since the overhaul.

Postaccident metallurgical examination of the crankshaft revealed that it had failed approximately 1.7 inches forward of the crankshaft oil seal. From this fatigue cracking origin, it propagated at a 45-degree angle to the axis of the crankshaft forward and aft. The origin was located inside the crankshaft bore at two corrosion pits.