Helicopters typically have a 14- or 28-volt direct current electrical system. A volt is a unit of measurement that expresses the capability of the force that pushes electrical energy. Amperes are the unit of measurement for a current and describe the measure of an electrical quantity that is available in the system. Small piston-powered helicopters use an engine driven alternator because they are light, low maintenance, and produce a uniform electric output— even at low RPMs. In a turbine powered helicopter, starter/ generator systems are used. Once the engine is started, the battery powers the starter, which turns the engine. After this initial jump, the generator is powered by the engine.
A voltage regulator is used to distribute the electrical supply; it prevents excessive voltage, which can cause damage to various electrical components. After the electricity is passed through the voltage regulator, it goes to a bus bar, which then distributes the current to different electrical components. The battery is mostly used to start the engine, but also powers a few things when the engine isn’t running— such as radios and lights— and is a good emergency electrical power source. An ammeter is used to monitor the electrical current flowing to and from the battery. An ammeter that is charging represents the fact that the battery is charging while a discharging ammeter indicates that the electrical load is exceeding the output of the alternator or the starter generator of a helicopter.
Electrical components can be selected through electrical switches. If the capacity of the switch is exceeded, a solid state relay may be used. When an electrical component is overloaded, a circuit breaker will pop out. A fuse will burn out when it’s overloaded and can be easily replaced. Caution lights may also be utilized to display when there is an electrical component malfunctioning.