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A Brief Comparison Between an APU and a GPU for Aircrafts

February 21, 2017 by · Leave a Comment 

APUs and GPUs both play a crucial role in onboard power configuration.

Written by: Start Pac

Both ground power units and auxiliary power units play a pivotal role in supplementing adequate power to an aircraft. Major airlines have separate units installed within the lanes of the runway to ensure that each aircraft that taxis can have access to a variety of power options.  This article will discuss the primary differences between a ground power unit (GPU) and an auxiliary power unit (APU).

The Basics

An auxiliary power unit’s primary function is supply onboard power for an aircraft – such as the small turbine. A GPU on the other hand, is a separate power unit that is either implanted within the ground or attached to a cart that can be driven out to the aircraft. The main difference between the two is the portability aspect.

The Similarities and Differences

They both provide a set stream of power to the aircraft, but a GPU rarely functions as a turbine. It can be used to heat an engine and be starting power source. An APU is typically used to power the onboard air conditioning system as well as the auxiliary power controls for the systems. The auxiliary power unit relies on the aircraft’s fuel to power it while a GPU functions independently on its own. Because a GPU is essentially a third-party portable power pack, it utilizes fuel, or other ways to power itself depending on the model, to operate. All in all, they both assist the aircraft engines when it comes to the starting process.

Locations and Priorities

The APU is also part of the airplane as opposed to the GPU being a separate component. It’s typically a small turboshaft engine that is located near the back of the plane. If you’ve noticed a somewhat small exhaust at the rear of an aircraft, that’s the auxiliary power unit’s structure protruding. The size is what allows it to start the airplane batter. If an APU is not functioning as it should, a GPU can come it and provide the exact amount of power to the aircraft and perform the same duties as an APU can, but in a separate portable form. Each of them can work in tandem with each other. For example, an APU is used throughout the flight. Once the plane is parked in the runway, a GPU can be brought in to take over the APU’s duties and save the engine from continuing to harness all the workload.