The Main Components of Aircraft Electrical Systems

The combination of thrust produced by the engines and lift produced by the wings is what allows an aircraft to fly. However, just as important in an aircraft’s operation is the intricate electrical system within it. The main components of an aircraft electrical system are the alternator/generator, battery, master/battery/alternator switch, bus bar, fuses, circuit breakers, voltage regulator, ammeter, and the associated wiring. In this blog, we will discuss each part in detail.

Alternator/Generator & Battery

The purpose of the alternator or generator is to supply electric current to the system and maintain a sufficient charge within the battery. Should the alternator or generator fail, electrical energy stored in the battery acts as a source of electrical power for starting the engine as well as a limited supply of electrical power.

Master/Battery/Alternator Switch

The master switch controls the electrical system. Turning the master switch on provides electrical energy to all electrical equipment circuits apart from the ignition system. The master switch controls components such as certain interior and exterior lights, radio equipment, fuel gauges, fuel pumps, stall warning system, pitot heat, and more. Some aircraft are equipped with a battery switch rather than a master switch, but the two achieve roughly the same thing. Furthermore, an alternator switch may be installed, allowing the pilot to isolate the alternator from the electrical system in the event of alternator failure. When the alternator is switched off, the entire electrical load is placed on the battery.

Bus Bar, Fuses, Circuit Breakers

A bus bar is used as a terminal within the electrical system to connect the system to the equipment using electricity as its power. This makes the wiring more simple and provides a common point from which voltage can be sent throughout the system. Fuses and circuit breakers are used in electrical systems to protect the circuits and equipment from electrical overload. It is important to carry spare fuses of the proper amperage in case they are needed to replace defective or blown fuses. Circuit breakers have the same function as a fuse but, rather than replaced, can be manually reset in the event of electrical overload.

Voltage Regulator

A voltage regulator is used to control the rate of charge to the battery by stabilizing the electrical output of the generator or alternator. The voltage output of the generator/alternator should be higher than that of the battery (a 12-volt battery should be fed by a generator/alternator system of approximately 14 volts).


Lastly, the ammeter is used to monitor the performance of the aircraft electrical system. It displays whether or not the alternator/generator is producing an adequate power supply and indicates if the battery is receiving an electrical charge. The ammeter display is configured with the ‘zero’ point in the center of the face with a negative or positive indication on either side. If the pointer is on the positive side, it means the battery is charging at that rate. If it is on the negative side, it means that more current is being used than replaced. As opposed to an ammeter, some aircraft have a simple warning light that indicates malfunction within the generator/alternator.

For all types of aircraft electrical system parts and much more, ASAP Components is here to help. Owned and operated by ASAP Semiconductor, we can provide you with a broad range of unique parts for the aerospace, civil aviation, defense, industrial, and electronics markets. Our dedicated account managers are standing by and ready to help you find all the parts and equipment you need, 24/7-365. 


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