How Do Generators and Alternators Power Civil Aircraft

The conversion of mechanical energy into electrical energy is fundamental to modern aviation, necessary for powering systems ranging from cockpit avionics and flight control instruments to cabin lighting and environmental controls. Generators and alternators serve as the critical mechanisms behind this energy transformation, ensuring that aircraft have a reliable and stable supply of electricity under all operating conditions. With this in mind, this blog will cover the basic functions of generators and alternators, highlighting the notable differences in their methods for powering aircraft.

Understanding Generators

Generators convert rotational energy from an aircraft’s main engines or auxiliary power unit (APU) into electricity, with torque often conditioned through an accessory gearbox to keep operation within an efficient speed range. In earlier aircraft, generators were typically direct-current (DC) machines that used a rotating armature winding inside a stationary magnetic field. The alternating current induced in the armature was mechanically rectified into DC by means of a commutator and carbon brushes. Although effective, this arrangement required frequent maintenance due to brush wear, arcing, and the stresses of continuous operation in flight.

Because most aircraft systems, including avionics, radios, lighting, and early flight instruments, originally operated on DC, these generators directly supplied 28 V DC to the electrical buses and charged the aircraft battery. If higher or steadier voltage was required, voltage regulators were employed to stabilize the output. Although AC generation has become the standard in modern turbine-powered aircraft, DC generators remain an important part of aviation history and are still found on some older piston-engine and turboprop aircraft.

Understanding Alternators

Like generators, alternators convert mechanical rotation from an engine or APU into electricity with a rotating electromagnet and stationary stator windings. In current iterations, both devices are very similar, but alternators have always centered on producing AC directly.

One particular operating advantage is that alternators can continue producing electrical power at lower engine speeds, which is especially valuable in piston-engine aircraft where older DC generators often stopped charging at idle or low RPMs. This capability was a key factor in the widespread adoption of alternators in light aircraft and started to close the gap between alternator and generator design. Moreover, alternators typically produce three-phase AC output, generating three waveforms offset by 120 degrees to deliver near-constant power, reduce electrical noise, and allow efficient operation of large motors and high-demand systems.

Furthermore, aircraft alternators also differ in form depending on application. Smaller units may use permanent magnet rotors for simplicity and reliability, while larger ones typically employ wound-field rotors to enable output regulation by adjusting excitation current. Across these variations, the emphasis is on lightweight, efficient, and consistent power generation tailored to the needs of light aircraft.

Source Alternators and Generators from Aerospace Aviation 360

In conclusion, both generators and alternators are the way aircraft achieve a dependable, flexible, and fail-safe electrical supply throughout all phases of flight, featuring diverse designs and operating principles to meet different power needs. For aircraft operators, access to high-quality generators and alternators is crucial when it comes time for replacements or upgrades, and Aerospace Aviation 360 has you covered.

On this website, we exclusively present generators, alternators, and thousands of other product types sourced from reputable manufacturers. You can easily locate all that you need with our convenient search tools, and when it comes time to request quotes and initiate procurement, our team will curate the most advantageous solutions for your consideration. With this in mind, be sure to check out our selection and connect with our experts today.