AAIB investigation to Aeronca 65C, G-BTRG
Propeller lost in-flight, Birchwood Airfield, North Yorkshire, 21 October 2021.
Summary:
Shortly after takeoff the propeller departed the aircraft and then the engine over sped. All six propeller bolts failed in fatigue due to a lack of pre-load. It is possible that a misinterpretation of an engine manufacturer’s requirement resulted in the incorrect bolt length being chosen. When the bolts were tightened to the correct torque they shanked, no pre-load was applied and failed due to normal propeller loads in fatigue. The aircraft was extensively damaged and the propeller was not recovered.
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Published 11 August 2022