Incident Overview
During a banner tow flight at an altitude of 1,200 feet above ground level, a portion of a propeller blade separated from the aircraft. The failed segment measured 21.6 inches from a two-bladed propeller with a total length of 38 inches per blade.
Sequence of Events
After the blade separation, the engine detached from three of its four mounting points and swung against the right side of the aircraft. The remaining propeller blade penetrated the cockpit structure but did not strike the pilot. The aircraft subsequently became uncontrollable and descended, impacting a field after striking trees in the backyard of a residence. The pilot sustained serious injuries.
Cause of Failure
The propeller blade failed due to fatigue cracking resulting from corrosion pitting. This metallurgical condition compromised the blade's structural integrity, leading to the in-flight separation.