Have you ever noticed a hole in the tail of the commercial jetliners? The hole is hiding a small but at the same time very important aircraft engine!
Every airliner has engines on either side; the number of engines in an airplane differs with the size of the plane. For example, the Airbus A320 has two engines while the superjumbo Airbus A380 has four engines, it is important to note that the A380-800 is $305,900,000 more expensive than the A320 not just because of two additional engines, but this is the subject of another article… Moreover, each jetliner has one more a much smaller engine in the tail, which plays a prominent role in smooth running of an airplane.
Let’s start from the beginning! The smallest engine at the very rear of the aircraft below the tail is called the auxiliary power unit (APU). It provides the necessary power to start the main engines, but the APU doesn’t help to move the plane. Without the APU, the main engines couldn’t be started from the cockpit. Usually, this technology helps when the plane is parked. Also, the pilots use the APU to power onboard electric systems ranging from cabin lights and coffee makers to various cockpit systems as well as provide airflow to the air conditioning systems.