Accident Narrative
While conducting a practice instrument approach on a dark night, the aircraft experienced a loss of electrical power. The airplane was above a low cloud layer. The pilot canceled the IFR clearance and informed air traffic control that he was losing electrical power and would fly back to home base under visual flight rules. He proceeded in a southerly direction, following roads, until he believed he had flown far enough to locate his home airport. Unable to find the airport, he made a 180-degree turn in an attempt to locate another airport, but became uncertain of his position. He elected to land on a large, well-lit parking lot. During the landing roll, the aircraft collided with concrete barriers.
Aircraft Electrical System Investigation
An automotive alternator was found installed on the airplane, with a non-approved support bracket that allowed for pulley misalignment, slack belt tension, and excessive vibration. The voltage regulator, alternator, and associated wiring harnesses were removed for functional testing. The voltage regulator and the alternator as separate units passed functional tests. However, the power input connector on the regulator fit loosely and allowed an intermittent electrical connection. Failure of that connection would allow the alternator to cease operating.
Previous Repair History
Approximately one month before the accident, the pilot reported intermittent low system output. In response, a mechanic removed the alternator for repair. The automotive shop that performed the work found the unit had acceptable voltage output but low amperage. A diode in the bridge rectifier was replaced, and the mechanic reinstalled the alternator on the engine. The mechanic stated that the alternator had been on the airplane for several years and that it never occurred to him to check the Type Certificate Data Sheet to ensure the alternator was approved for airplanes.