Grumman American Avn. Corp. AA-5B N28862 accident near Milford, Indiana

Probable cause

A loss of engine thrust due to the separation of a section of one of the propeller blades as a result of fatigue failure of the propeller because of corrosion. Contributing to the accident was the failure of the mechanic to detect and address the propeller corrosion during the annual inspection.

NTSB analysis

The airplane was in cruise flight when the pilot heard a "loud bang followed by a violent vibration." He secured the engine and executed a forced landing to an open field. A postaccident examination revealed that a 20-inch length of one of the propeller blades had separated. Metallurgical examination revealed a fatigue failure of the propeller blade initiating from an area of corrosion. Corrosion pitting was observed over the entire cambered surface of the blade. The propeller had accumulated 2,326 hours total time in service. The most recent annual inspection was completed approximately 2 months prior to the accident. Federal Aviation Administration publications and the manufacturer's documentation recommended a detailed visual inspection of the propeller for corrosion during an aircraft annual inspection.

Text from the NTSB. Open the NTSB docket for CEN09LA132 for the full record.