Incident Details
A pilot noted a negative reading on the ammeter during flight and cycled the alternator switch with no effect. Before landing, she activated the runway lights and discussed wind conditions with a departing pilot. The aircraft experienced a complete electrical failure while on the downwind leg to land, after the control tower had closed. As a result, all external lighting and communication radios in the aircraft became inoperative.
Sequence of Events
A vehicle driver was conducting a required inspection on runway 32. The driver, monitoring the tower frequency with a handheld radio, heard a discussion but could not discern the details. She observed the runway lights illuminate and believed they were activated by the departing aircraft. She announced her field position and intentions using the ground control frequency.
The pilot landed the aircraft on runway 20 and began the rollout. At the same time, the vehicle driver was on runway 32, crossing runway 20. Subsequently, the aircraft and vehicle collided at the runway intersection.
Investigation
The aircraft's alternator and voltage regulator were removed and tested after the incident; both were found to be operational. The overvoltage unit was not recovered, and the reason for the loss of electrical power was not verified.