I’ve noticed that many passenger jets, even those without an engine mounted in the tail, seem to have an exhaust port in the tail of the plane. You can tell that hot gases are being exhausted from the port, so it’s like a car tailpipe. But what is its purpose? Where are the hot gases coming from?
I’m guessing you mean something like THIS
That is an engine on top of the plane in front of the vertical fin. And that is the exhaust for that engine.
If you mean something else, could you post a pic? I can think of no reason to have a rear exhaust other than for a third, center mounted, engine.
Other than for an APU of course (after reading susbsequent posts :smack: )
That rear exhaust port is used to vent the Auxiliary Power Unit, which provides power for the plane for purposes other than propulsion.
Probably APU.
Thanks. I googled every combination of ‘airplane rear exhaust port’ that I could think of, no joy. Now my ignorance done bin fitted.
Where’s the air intake for that sucker? The wikipedia article talks like the APU is run off of compressed air, implying the plane actually carries the air supply for the APU, but the wording in the article is not clear. Do you guys know where the air for combustion comes from?
No, the compressed air is used to spin up the main engines. The APU provides power to drive the air compressor.
Since an APU doesn’t generate thrust, it doesn’t need a lot of air. You can see the air intake on a 747 here: Boeing 747-4H6 - Qantas | Aviation Photo #0573755 | Airliners.net I think the intake is covered up when the APU isn’t running.