Incident Overview
A pilot experienced a landing gear malfunction when the gear would not extend electrically. An attempt was made to manually extend the gear using the emergency extension system. However, the hand crank would not turn in either direction. While force was applied to the cranks, the chain drive failed. The aircraft was subsequently landed with the landing gear retracted.
Component Examination
After the incident, the emergency extension system was disassembled for inspection. The examination revealed that a shaft, part number 0843400-50, was bent. Additionally, gouge marks were found on a tooth of a bevel gear, part number 0843400-49. The manual extension chain, part number 500000-52, which connects the hand crank to the bevel gears, had broken. No other discrepancies were evident in the landing gear system.