What happened
On December 18, 2011, a Cessna 182, registration F-BLEC, departed Couhé-Vérac for Toussus-le-Noble under VFR night conditions. During the cruise phase near Chartres, air traffic control notified the pilot that radar contact had been lost. Shortly after this notification, the pilot observed a red battery warning light on the instrument panel.
Following the electrical failure, the pilot lost the ability to communicate with controllers. To preserve remaining battery power, the pilot deactivated the radios, transponder, pitot heat, and the onboard GPS. Because the pilot could not verify the status of runway lighting at alternative aerodromes and assumed the destination lighting would be active due to the filed flight plan, the decision was made to continue to Toussus-le-Noble.
As the flight progressed, the pilot lost VOR signal reception and was forced to navigate using a portable GPS unit placed on the rear seat, utilizing the autopilot to maintain course. Operating without interior lighting and relying on headlamps and flashlights, the pilot eventually identified another aircraft in the traffic pattern. The pilot successfully integrated into the downwind leg of runway 25L and landed without the use of flaps.
The investigation
Maintenance inspections following the incident revealed that the alternator load circuit breaker had tripped, preventing the alternator from delivering power to the electrical system. The specific cause of the breaker trip could not be determined. The investigation also noted that the red overvoltage warning light activates during both alternator failure and low voltage at the regulator.
Findings
- The primary cause of the electrical failure was a malfunction within the electrical system that caused the alternator circuit breaker to trip.
- The pilot's error in diagnosing the failure contributed to the situation; the pilot prematurely concluded the alternator had failed without checking the circuit breakers.
- The pilot did not utilize a checklist during the emergency, and the relevant checklist for this specific failure did not include a requirement to check the circuit breakers.
- The circuit breakers are located beneath the instrument panel, making them difficult to access during an emergency without sufficient light.