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The private pilot/owner of the experimental, amateur-built Zenith CH 750 reported that, about 15 minutes into the local flight, the engine started “skipping” before completely losing power.
He set up for a forced landing to an open area near DeLeon Springs, Florida.
During the descent, he maneuvered to clear power lines. The airplane touched down at a steep descent angle, nosed over, and came to rest inverted, which resulted in substantial damage to the airframe.
The airplane’s engine used an electronic control unit instead of magnetos and required at least one of the airplane’s two onboard batteries to provide electrical energy to the ignition system for the engine to operate.
Post-accident examination of the airplane revealed that both of its batteries were discharged. After the batteries were charged, the engine was started and ran normally. The alternator also charged the batteries normally.
The cockpit instrument panel switch that enabled the alternator to supply energy to the airplane’s electrical system, and thus charge the airplane’s batteries, was unlabeled. When the switch was placed in the unlabeled on position, the alternator field wire received power and the alternator charged normally.
The pilot reported he may have inadvertently left it in the off position during the flight. With the switch in this position, the engine would have continued to run until the selected battery lost its charge.
The pilot also reported that he did not use a checklist when operating the airplane.
It is likely he failed to activate the airplane’s alternator, which resulted in a discharge of the selected battery during the 15-minute flight. The subsequent loss of electrical power eventually resulted in the total loss of engine power.
Additionally, the airplane was not equipped with an alternator warning light as recommended by the engine manufacturer. Had the airplane been equipped with such a light, the pilot might have realized that he had failed to turn the alternator on and that it was not providing energy to the electrical system to sustain the charge of the selected battery.
Probable cause: The pilot’s operation of the airplane with the alternator switch in the off position, which allowed the selected battery to discharge and resulted in an ignition system failure and a total loss of engine power.
This September 2018 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended
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