Here's one for you @The.Black.Templar

[Mwalimu-G]

Tech
Airplanes have a secret engine hidden in the tail
PULSE

December 1, 2017 4:52 PM

Your plane has a hole...on purpose.

Most commercial jetliners have a small hole in the tail. Have you ever wondered what this hole is there for? Following is a transcript of the video.

Most jetliners have a hole in the tail. Why do airplanes have this hole? Check out the typical commercial jetliner. It has main engines on either side to generate thrust. But there's another engine hidden int he back of the tail. Called the auxiliary power unit (APU) It's the smallest engine on a plane.
But you could say it's the most important one of all. It provides the necessary power to start the main engines. Without the APU, the main engines couldn't be started from the cockpit. Without the APU, the main engines couldn't be started from the cockpit.
Usually, the APU only runs when the plane is parked. It also powers onboard electronics like cabin lights and air conditioning. One the plane heads for the runway the main engines take over. And the APU is turned off. So, the next time you lift off, thank that tiny hole in the tail.

 

[Anglututu]

Everyday people become aware of how things work, good article.
What he failed to mention is when the apu is unserviceable you'll need ground power to power the aircraft while it's parked.
Picture like a generator like thing, like those ones used to power whole buildings, but in wheels.
Modern day, ground power is built into the airport infrastructure so you do not need the mobile ground power.
In so many words the apu acts like the car battery in a vehicle.
That's the simplest way to put it.
The only stupid thing the writer has said is to thank that little hole.
Its like thanking the car's exhaust pipe exit.

 

[emali]

most jetliners actually have one more "engine" called.. ram air turbine (RAT).. this is deployed in emergency situations when all engines have failed to provide power to the most crucial instruments..
from Wikipedia:
The RAT generates power from the airstream due to the speed of the aircraft. If aircraft speeds are low, the RAT will produce less power. In normal conditions the RAT is retracted into the fuselage (or wing), and is deployed manually or automatically following complete loss of power.