When you think about a commercial airplane, the first thing that may come to mind is massive jet engines. But did you know there’s another power source onboard most commercial aircraft?

It’s called an auxiliary power unit—or APU—and it plays a vital role in keeping an airplane functioning while on the ground. Let’s look at what an auxiliary power unit does in airplanes and how it helps keep passengers safe and comfortable during their flights.

What Is an Auxiliary Power Unit?

An APU is a small turbine engine that provides power to an airplane when the main engines are not running. It powers the airplane’s electrical system, air conditioning, and other systems while the plane is on the ground. The APU also starts the main engines when it’s time for takeoff. Think of it like a car battery that helps crank the engine to get the car going.

Why Do Airplanes Need an APU?

An APU is essential for keeping an airplane functioning properly while on the ground. Without an APU, the plane would have to rely on external power sources—such as a ground power unit or a generator—to keep its systems running. This source would be inconvenient and add unnecessary wear and tear to the plane’s engines. With an APU, the plane’s engines are not running and therefore aren’t subject to wear and tear.

How Does an APU Work?

An APU typically runs on jet fuel, but some newer models can run on aviation gasoline or even batteries. The APU draws air from outside the plane and compresses it using a fan. This compressed air then powers the turbine, which powers the generators that provide electricity to the plane’s systems.

The next time you’re boarding a commercial airplane, take a moment to think about what an auxiliary power unit does and its importance. This small but mighty engine plays a vital role in keeping the plane running smoothly on the ground and in the air. Without it, airplanes would be on the ground much more often—and we’d all be stuck in airports much longer!

If you are an aviator and need to know more about finding an APU or other maintenance parts, you can find them with the aircraft part number lookup on our Seattle Aviation Solutions website.

Not only can you find the parts you need, but Seattle Aviation Solutions can provide support and maintenance to ensure your plane is in the best possible condition. Visit our website today to learn more about how to keep your aircraft running safely and efficiently.