Accident Narrative
The airplane was in cruise flight when a portion of the propeller blade separated. The engine then began to violently vibrate. The pilot executed a forced landing. During the forced landing, the airplane collided with cactus plants before touching down. The airplane hit the ground hard, causing the landing gear to separate.
Investigation Findings
The Safety Board's Materials Laboratory examined the remainder of the propeller blade. The examination revealed fatigue cracking. At the origin of the crack was a corrosion pit. High magnification optical examinations showed numerous small shallow corrosion concentration areas embedded on both the camber and flat surfaces. These findings indicated that the blade had not been properly dressed. Paint and conversion coatings covered many of the pits and corrosion areas.
Maintenance History
The propeller was overhauled on March 25, 2002, and had accumulated about 700 hours of total time since the overhaul. Logbook entries recorded that maintenance personnel removed propeller nicks on October 30, 2002.
Regulatory Reference
FAA Advisory Circular 43.13-1A, Section 3 "Repair of Metal Propellers," paragraph 585(a) discusses procedures for the repair of aluminum propellers. The reference addresses rounding out nicks, scars, cuts, etc., advising to "exercise care to remove the deepest point of the injury."