What happened
While approximately 26 miles from the destination airport, a commercial pilot observed signs of an electrical failure when the instrument panel ammeter indicated zero. In response, the pilot deactivated all electrical equipment on the aircraft.
Upon arrival at the destination airport, the pilot attempted to extend the landing gear by placing the extension handle in the down position. However, the gear failed to extend, and the gear down lights remained unlit. To execute an emergency gear extension per the flight manual, the pilot reduced the airspeed to 87 knots and held the emergency gear lever in the "EMERGENCY DOWN" position while fish-tailing the aircraft.
To verify the status of the gear, the pilot observed the airplane's shadow and noted that the gear appeared to be down. During the landing roll, the left main landing gear collapsed, causing the left wing to strike the runway surface.
The investigation
A post-accident examination of the aircraft revealed that a voltage regulator failure had occurred, which caused the loss of electrical power. The aircraft is equipped with retractable tricycle landing gear operated by an electrically powered reversible hydraulic pump. While the emergency extension handle is designed to manually release hydraulic pressure to allow the gear to free-fall into position, a complete electrical failure prevents the gear down lights from illuminating.