APU’s in Airplanes

APU’s in Airplanes

Auxiliary Power Units or APUs have become synonymous with efficiency not only on the ground in trucks, but also in the flying machines of the sky. Airplanes have a variety of uses for APU’s and understanding their function when it comes to aircraft safety and power is important for anyone who is in the aviation industry.


Most of the time, the APU is located in the back of the plane, generally in the tail of the aircraft. Those who do not understand the parts of an aircraft may be wondering why it is located in the tail part of the plane. Having the APU in the tail means that it is out of the way of the workers that are underneath the plane working before take off and reduces the amount of noise in the main cabin. Despite its smaller size in comparison to other parts, the APU is powerful enough to work throughout the entire aircraft system.


This turbine engine functions in the same way as any jet engine. Once started, it takes in air, compresses it and adds a fuel mixture to ignite. It provides no thrust, but powers both an electrical generator, provides bleed air and in some cases hydraulic pressure. The electrical generator is what powers not only the cabin lights but also the general avionics that are on the flight deck. On the other hand, the bleed air not only provides the all-important AC, but is also responsible for providing enough air to get the main engine started.



“Bleed air” is the air that is produced by the compressor that is powered by the APU. Extremely powerful at around 40 PSI, once the air reaches the starter motor it activates the entire system. The fans are large but spin rather easily, as proven by how wind can spin them while the plane is on the tarmac. When on the apron, the APU is almost always activated, providing enough power to not only reduce fuel consumption but allow for staff and flyers to be comfortable as they wait for take off.


Having the right aircraft APU service is essential to keeping you and your staff safe in the air. Our hangar and engine repair facilities have a global reach that will allow us to provide you with the exceptional service you have come to expect from us. We are proud to service your Honeywell GTCP 36-100 and GTCP36-150 APU to keep you operating as safe and comfortable as possible.