Nov 172009
I just realized airplanes have sort of a smoke exhausting pipe below the tail’s vertical flap… What kind of engine do they have inside to produce that much smoke and what’s its purpose??
Thanks!!
This smoke or hot air or whatever it is can be seen when the flight is boarding even while the tubofans are stopped…
The APU, or auxiliary power unit is often running so the A/C units can keep the interior cool while boarding. These units are basically a small jet engine that runs on the same fuel as that MAIN engines.
Modern jet engines produce a LOT less smoke than they did back in say, the 60’s. Back then they made o LOT of smoke.
Better engines and better fuel has cleaned things up a lot.
it isn’t smoke it is the exhaust coming out hot and hitting the cold air up there.
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I *think* what you’re referring to is the contrails that you see behind an airplane as it travels through the sky, right??
It’s a "vapor trail" created by the airplane …
…read more about it in the link below.
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http://en.wikipedia.org/wiki/Contrail
The APU, or auxiliary power unit is often running so the A/C units can keep the interior cool while boarding. These units are basically a small jet engine that runs on the same fuel as that MAIN engines.
Modern jet engines produce a LOT less smoke than they did back in say, the 60’s. Back then they made o LOT of smoke.
Better engines and better fuel has cleaned things up a lot.
References :
That’s the auxiliary power unit or APU. A small turbine engine used on the ground to supply pnuematics for engine start and air conditioning on the ground as well as electrical power. Once the engines are started, the APU is shut down and the engines and their respective generators do all of that in flight. But it shouldn’t be producing much smoke. Yikes, run.
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The APU. A small jet engine, just to power the A/c electrics and other systems when the big fans aren’t running.
The average APU in a modern jet airliner is more powerful than the first Jet engine that flew (Back in the late 1940’s)!
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an apu is usually a small turbojet which is an old technology as far as jet engines go. Even some large aircraft use turbojets. I.E. B737-100, B707, GII. The B-52 used the same engine as the 707 however, the B-52 also used water injection for more thrust which created a large plume of smoke when taking off.
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What you see is the exhaust from the Auxiliary Power Unit, or APU. This provides air for starting the engines, and for air conditioning on the ground. It also supplies 400 cycle 115 volt
electrical.
You will not see this on a Boeing 727. The location of the APU on that plane is the keel beam area (belly). This is because the inclusion of the APU was an afterthought. As a result the 727’s APU exhaust is located on the upper surface of the right wing.
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If it a jet type engines it is because the engine is using an oil base fuel and is not being fully burned. All tail pipes of jet engines produce oily exhaust
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A?P mechanic
It’s the Auxilary Power Unit and it’s just a small turbojet engine that generates electricity for the lights, air conditioning and other stuff when the main engines are not running. It shouldn’t produce black smoke unless it’s a really old plane, but turbojets are dirtier and produce more smoke than turbofans anyway so it might.
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my brain
That is the Aux Power Unit.
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