ERA19LA177

The pilot was conducting a personal flight in the experimental amateur-built airplane, and after departing the local area, noticed the DC electrical bus voltage decrease from 13.6 volts to 12.5 volts. He initiated a turn back to the airport and about 2 minutes later, the DC bus voltage decreased to 0 volts and the engine stopped producing power. The pilot performed a forced landing to an open field, during which the airplane sustained substantial damage. The airplane was constructed such that the engine was electrically dependent on a single alternator and a single battery to provide required electrical power to operate the fuel pump and ignition systems. Examination of the airplane revealed that the alternator circuit breaker, which was located behind the instrument panel and out of view of and inaccessible to the pilot, was tripped. Based on the pilot's description of events, it is likely that an electrical load drew an excessive current through the alternator circuit breaker, which resulted in it tripping and interrupting the electrical power supplied by the alternator. The engine's electrically-operated fuel and ignition systems continued to function on battery power for about 2 minutes before the engine stopped running. The pilot's reported inability to restore electrical power (and subsequently, engine power) at a low altitude resulted in the forced landing.

On May 16, 2019, about 1435 central daylight time, an experimental amateur-built Zenith CH750 STOL, N750GZ, was substantially damaged when it was involved in an accident near Savannah-Hardin County Airport (SNH), Savannah, Tennessee. The pilot and passenger were not injured. The airplane was operated under the provisions of Title 14 Code of Federal Regulations Part 91. According to the pilot, he performed a preflight inspection of the airplane with no anomalies noted. He stated that he checked the battery voltage after engine start-up, then departed SNH. While in flight, he observed a drop in the direct current (DC) electrical bus voltage from a normal value of about 13.6 volts direct current (vdc) to about 12.5 vdc. He initiated a turn back to SNH and about 2 minutes later, the DC bus voltage dropped to 0 vdc and the engine stopped producing power. The pilot selected an open field and preformed a forced landing. After the accident, the pilot noted that the alternator in-line circuit breaker located under the instrument panel, was tripped. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed substantial damage to the firewall and additional damage to the nosewheel and rudder pedals. An inspection of the alternator circuit breaker revealed that its location underneath the instrument panel was not visible or accessible to reset during flight. The airplane was constructed such that the engine was electrically dependent on a single alternator and a single battery to provide required electrical power to operate the fuel pump and engine ignition systems. Following the accident, the pilot installed a backup battery in the airplane.