This January 2009 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Grumman Tiger. Injuries: None. Location: Milford, Ind. Aircraft damage: Substantial.
What reportedly happened: The airplane was in cruise flight when the pilot heard a loud bang, followed by a violent vibration from the engine. The pilot shut down the engine and performed a forced landing in an open field.
The post-accident examination revealed that the propeller had lost 20-inches of blade due to fatigue initiating from an area of corrosion. Corrosion pitting was found 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 two months before the accident. FAA publications and the manufacturer’s documentation recommend a detailed visual inspection of the propeller for corrosion during the annual inspection. An Airworthiness Directive required factory inspection and reconditioning for propellers with 500 hours or more of flight time. Propellers inspected and/or reworked were to be identified with the suffix letter K after the serial number. The accident propeller included a K suffix after the serial number consistent with compliance to the AD. At the time of the accident, the propeller had accumulated eight hours since the annual inspection.
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.
For more information: NTSB.gov