What happened
The aircraft was operating en route in instrument meteorological conditions when it experienced a total loss of electrical power. Following this failure, the pilot descended to visual flight rules conditions and elected to land at Weiser Airport. During the approach, the pilot lowered the landing gear using the electric system but did not receive the standard green down and locked indication. Suspecting a malfunction, the pilot then operated the emergency extension handle, yet still failed to see the green light confirming the gear was secure. Upon touchdown, the main gear retracted into the fuselage. Analysis indicated that had the pilot continued to manually pump the emergency system, the gear would have successfully locked in the down position.
The investigation
Examination of the aircraft revealed that the alternator fan blade had separated from its assembly and exited through the engine cowling. This separation created significant vibration within the engine compartment. The resultant mechanical shaking caused the alternator ground wire to detach from its attachment point. This disconnection was the direct cause of the total electrical failure experienced by the crew during flight.
Findings
The primary contributing factor was the separation of the alternator fan blade, which led to excessive vibration. This vibration caused the alternator ground wire to separate, resulting in a complete electrical system failure. The pilot's inability to confirm gear position due to the power loss compounded the severity of the incident, leading to main gear retraction during landing.
Safety message
Pilots should be aware that total electrical failures can disable critical gear indication systems. In such scenarios, relying solely on visual or electronic confirmation may be insufficient; manual pumping procedures must be continued until mechanical lock is verified by other means.