What happened
While performing a cruise flight near an airport, the propeller of the aircraft separated from the engine. Following the separation, the pilot received vectors to the airport and entered the landing pattern. Due to a strong tailwind, the downwind leg of the pattern was extended.
During the final approach, a strong headwind caused the aircraft to land short of the intended area. During the subsequent landing roll, the aircraft collided with two fences. The occupants were not injured.
The investigation
An examination of the aircraft revealed that six propeller mount bolts had failed due to fatigue. This failure was a result of the improper placement of a propeller mounting shim. Specifically, the shim was not placed between the engine crankshaft flange and the starter gear flange as required.
According to the aircraft manual, the propeller mount bolts are susceptible to failure from relative movement between the two flanges if the shim is not installed correctly. The correct placement for the shim is between the propeller flange and the starter gear flange. Records indicated that a sudden engine stoppage occurred approximately 45 hours prior to the accident, which had resulted in the removal, overhaul, and reinstallation of the propeller.