How Does an Aircraft Engine Produce Electricity?

All aircraft systems, from the reading lights to the entertainment screens are powered by electricity. Similar to a majority of engine-driven vehicles, aircraft produce electricity through the use of an alternator or generator. To do this, these devices utilize the engine’s rotational power to spin magnets mounted within a field coil to generate electricity.

While the electrical system is not necessary for flight or aircraft movement, it still serves as one of the most critical systems on board. In fact, electricity is utilized for safety equipment, countless cockpit instruments, environmental systems, and entertainment functions. The importance of electricity varies according to aircraft, with many airplanes lacking any electrical system at all. For instance, ultralights, or classic planes such as the J-3 Cub, do not need power as they do not have any electronics.


Without a generator or alternator, an aircraft will not require a battery or any of its wiring, making it lighter and less expensive to operate. Moreover, if a plane lacks a battery, then it does not have a starter either. Nonetheless, having a little bit of power is incredibly helpful. As such, most small aircraft are equipped with an alternator. The alternator usually charges  the battery, which is utilized to store energy to help start the plane and run equipment if the alternator fails.

The electrical system in aircraft can be divided into four parts. There must be a source of electricity, a battery for storage, a power distribution mechanism, and items on board that use the power. With so many areas that use electricity, pilots are expected to learn each component of their aircraft’s system, so that they troubleshoot problems when necessary. Today, alternators are one of the most common ways of generating power to piston-engine airplanes in particular.

It is worth noting that some planes use more electricity than others. A good way to determine how vital electricity is to an aircraft is by identifying the amount of complicated electronics in the cockpit. For instance, autopilots utilize electrical servos to move flight controls, and some airplanes use electrical power to retract and extend the landing gear or extend the flaps.


A generator produces electricity in the form of direct current (DC). Unfortunately, it needs to spin at a fast constant speed to generate power. For this reason, small aircraft with fluctuating speeds during flights do not use generators. Similarly, some older aircraft models with generators on board had certain limitations. For example, if the plane idled on the tarmac for too long prior to takeoff, the generator would not be able to supply sufficient power to keep the batteries charged. Keep in mind that generators can be used as starters too.

Auxiliary Power Units (APUs)

Auxiliary Power Units (APUs) are also used as a means of providing electricity to aircraft, especially for large turbine airplanes that need a lot of power. APUs are considered compact turbine engines, and they are mounted in the tail section. They run power generators and create bleed air to help start the main engines. While reasonably small, they are big enough to make electricity to use in the plane.

Ground Power Units (GPUs)

Ground Power Units (GPUs) are found on the tarmac and are used to help aircraft start when the airplane’s batteries are dead. Essentially, they work like jumper cables for planes. In addition, they are utilized to provide electricity to a plane without running the engines. Due to the fact that running the motors is expensive and burns large quantities of fuel.


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