What is an APU?

Anybody can appreciate the complexity of an aircraft, especially knowing that thousands of individual components work together to keep the airplane flying. Since modern airline travel is predicated on safety above all else, almost every aircraft system has a backup device in case of failure. One of the most indispensable but overlooked aircraft components is the Auxiliary Power Unit, or APU. In this blog, we will inform you on what an APU does and how it facilitates power and exhaust within jet aircraft.

The APU is an engine that sits in the back of an aircraft. At face value, it works like any other engine on the fact that it takes in air, compresses it, mixes in fuel, and eventually ignites the mixture. The main difference is that the APU does not generate any thrust. Instead, the output created by the engine is used to power electrical systems and an air compressor. These two systems provide power to different parts of the plane. During the startup sequence, air from the APU is sent to a motor in the main engines to help get them started. Besides helping in the startup sequence, the electrical generator of the APU is used to power the cabin lights and avionic systems.

At first, it may seem counterintuitive to situate a component that lets air into the main engines so far away from such parts. The truth is, there is limited real estate near the main engines, so that space is often used to house more vital components like fuel tanks and lines. Additionally, the compressed air coming from the APU is usually high in pressure and has no problem making its way to the engines. Since the power generated by the APU is mainly used during startup, it typically remains off during the entire flight and is only activated while taxiing. The air intake for the APU is found in the back of the plane as well. When the system is engaged, panels on either end of the fuselage will retract and allow for air intake. After use, the exhaust from the APU exits through a pipe at the rear of the airplane.

Besides helping facilitate startup, APUs serve the extremely critical role of acting as backup power source in the case of generator failure. If one generator were to fail during flight, the pilot could activate the APU to compensate for the loss in power. In fact, during the famous "Miracle on the Hudson" emergency in 2009, investigators found that Captain Sullenberger's early activation of the APU proved vital in maintaining power to all systems.

The APU is yet another example of a crucial aircraft system that must remain up to date and well-performing. If you are in the market for any aircraft component, Aerospace Buying has made the process easy and affordable. We are owned and operated by the well-known ASAP Semiconductor, and as such, have access to an unmatched inventory and buying power. Aerospace Buying has leveraged those factors to bring you high-quality aviation parts at a competitive cost with unparalleled shipping speeds. Furthermore, we operate with AS9120B, ISO 9001:2015 certification, and FAA AC 0056B accreditation which means you can always rely on the integrity of the products we distribute. In addition, we have access to a robust international supply chain which allows us to offer expedited shipping on most items. For customers facing AOG situations, our team members are available whenever to discuss possible same-day shipping on select in-stock items. As we believe in responsible sourcing, we are the only independent distributor to offer a no-China sourcing pledge. Please browse our inventory today and receive a personalized quote in just 15 minutes or less.

  1. Posted on October 4, 2021
  2. aerospace parts

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