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What Are Aircraft Power Generators?

Have you ever sat in an airplane and wondered where all the power comes from? So many of the components onboard are electric, from the reading lights to display screens in the cockpit. It is relatively simple to see how those enormous jet-fueled turbine engines produce thrust but the same power and hot air that is produced by these engines are also used to power many onboard systems including the hydraulics, pressurization, de-icing, and electrical systems. In this article, we will discuss how electricity is used in aircraft as well as what systems have been designed to generate it.

How Is Electricity Used on Aircraft?

Though aircraft can fly without the use of electricity, the electrical system on an airplane is still one of the most critical systems onboard. Electricity is used for safety equipment, many of the cockpit instruments, environmental systems, and entertainment functions. Aircraft without any electronics on board may not need an electrical system, but they would be missing a crucial system for flying at night: lighting. More than that, if a plane does not have a battery, then it cannot have a starter or built-in radio. On smaller aircraft, it may be beneficial to leave out a generator or alternator to reduce the overall weight and operational costs. Very small planes can be safely started manually, and rechargeable handheld radios can be employed. However, these limitations are generally not suitable for most pilots, especially within the commercial sector.

What Is an Aircraft Alternator?

The electrical system in an airplane can be divided into four parts: an electrical generator, a battery to store the energy, a way to distribute power, and the items on board which use the power. Alternators are the most common way for small piston-engine aircraft to generate their power. This power is used to charge the battery that stores the energy necessary to start the plane and run equipment if the alternator fails. It is also used to run the lights, communication radios, and navigational equipment. Some planes are more electrical than others and use complex systems such as the autopilot feature, which requires electricity to function. Besides the autopilot system, planes may use electrical power to operate landing gear, or extend control surfaces. For these reasons, alternators are useful on small aircraft for supporting various equipment and starting up the engine.

What Is an AIrcraft Generator?

On aircraft, the generator is a device which spins at a fast, constant speed to create direct current electricity. In general, it is not well-suited for smaller planes where the engine speed changes frequently throughout flight. However, on larger airliners, generators can be a more powerful source of electricity than alternators, supporting many more systems on the vehicle. Due to their capability to create a large amount of power, generators are often used on airliners and other large jet aircraft.

What Is an APU?

Airliners and large turbine airplanes require a lot of power, and the battery power alone is not enough to start the engine. To resolve this issue, large airplanes are commonly equipped with an Auxiliary Power Unit (APU). This device is a small turbine engine that is mounted in the tail section, which runs the power generator and creates bleed air. APUs require less power to be started up and can therefore be activated with the battery. However they are still large enough to make enough electricity to use on the plane and recharge the battery. In addition, the bleed air can be used for other mechanisms onboard, including many of the environmental systems.

What is a GPU?

A Ground Power Unit (GPU) is a type of electric generator used on the tarmac to help start batteries and run any other electronics that must be kept on while an aircraft is grounded. APUs are powerful enough to support a jet aircraft, but they generate a lot of noise and are usually banned from use on the tarmac. If the aircraft is sitting idle for a while, GPUs can be useful generators for maintaining power to the heating or air conditioning systems, navigational equipment, and more.


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