Summary: During the airplane starting sequence, where does the compressed air actually come from?
During an airplane starting sequence, the engine core relies on a substantial amount of compressed air. However, where does this air come from? For most basic turbines, it’ll come from one of three sources.
Auxiliary Power Unit (APU)
The APU is a small turbine engine that’s located near the tail of the plane and provides compressed air and electricity throughout. Additionally, it powers the aircraft’s electrical systems on the ground and acts as a backup for all electrical needs. It can also send compressed air to the engines’ air turbine starters. Normally when you start a plane, it’ll first activate the APU.
Air Start Unit (Huffer Cart)
The huffer cart, also known as an air start unit is an air compressor that activates by hooking on to the side of an aircraft. It provides compressed air needed to start an engine – which functions in a similar fashion as a military tank starter does.
Turbine engines tend to push air towards other aircraft components like the heated anti-ice systems or the cabin pressurization system. This compressed air can be easily routed from one engine to another. A technician can simply open the bleeds on one engine and open the crossbleed to the other engine, and it’s then ready to start.
Whatever the process may be, airplane engines require a significant amount of compressed air. With so many different types of technology available to aviation crews in this day and age, there is an increase in versatility and flexibility. Maintenance teams are now purchasing these equipment pieces at low prices due to the vast amounts of competition out there. For instance, some companies will purchase an assortment of aircraft maintenance equipment from Start Pac in order to satisfy all of their planes’ needs.