Event Summary
During a flight, the pilot was notified that the aircraft's Mode C encoder signal was not being received. Shortly thereafter, the airplane began losing electrical power. The loss progressed until all communication and navigation equipment failed, including a hand-held GPS that drew power from the aircraft's batteries. Despite the electrical failure, the pilot continued the flight using pilotage—navigating by visual reference to landmarks.
Fuel Indication and Landing Decision
The pilot reported that when the fuel gauges indicated 10 gallons in each tank, he decided to perform an off-airport landing on an interstate highway. He attempted to lower the landing gear but was unsuccessful. No attempt was made to manually pump the gear down. Due to traffic on the interstate, the pilot was forced to initiate a gear-up landing on a service road adjacent to the highway.
Power and Engine Performance
The pilot stated that the engine maintained full power throughout the entire sequence, from the onset of electrical problems through the landing.
Post-Accident Inspection
After the accident, the batteries were recharged and replaced in the aircraft. Both alternators and alternator switches were tested and operated normally. No evidence of charging circuit malfunction or failure was noted.