What happened
The aircraft experienced a complete electrical failure during flight. In response to this malfunction, the pilot initiated a manual extension of the landing gear system. According to the pilot's account, he operated the landing gear handcrank until he encountered heavy resistance. Based on this feedback, the pilot believed that the landing gear had successfully extended and locked into the down position.
Despite these indications, the aircraft landed with the landing gear in an unsafe configuration. During the landing roll or upon impact, the landing gear collapsed, resulting in significant damage to the airframe and undercarriage components.
The investigation
A post-accident inspection of the airplane was conducted to determine the root cause of the incident. The examination focused heavily on the electrical system, given the reported total failure. Investigators discovered a broken brush within the alternator unit. This mechanical failure in the alternator prevented the generation of electrical power, which likely contributed to the inability to verify the gear position electronically or via standard indicators.
Findings
The primary factor leading to the accident was the pilot's reliance on tactile feedback from the handcrank rather than definitive confirmation of gear lock. While heavy resistance is often an indicator of gear engagement, it does not guarantee that the gear is fully down and locked in all aircraft configurations or conditions. The broken alternator brush was a critical mechanical failure that necessitated the manual extension procedure.
Safety message
Pilots operating aircraft with manual landing gear extension systems should be aware that tactile feedback alone may not always confirm proper gear lock. It is essential to utilize all available means, including visual confirmation or alternate indicators if possible, to verify gear position before landing.