3rd turbine in the tail?
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3rd turbine in the tail?
This is probably the first time I've posted on this forum, but had a curiousity that I wanted to lay to rest. On some aircraft there is a 3rd turbine in the tail section of the airplane.. I've heard (from where, I can't remember) that this is primarily used to generate power for the aircraft, and is not necessarily used for thrust. Is this just myth or is it actually used to power the aircraft while in flight, etc? Thanks in advance!
Joel
Joel
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Hello mandenbar,
It is what we call a Auxillery Power Unit (APU).
It's primary use is to provide the aircraft of electrical power and air to run the airconditioning packs and to start the engines.
The unit is mostly used on the ground but can also be used in flight as a back-up when one of the engine generators fails.
hope this helps.
regards Vincent
It is what we call a Auxillery Power Unit (APU).
It's primary use is to provide the aircraft of electrical power and air to run the airconditioning packs and to start the engines.
The unit is mostly used on the ground but can also be used in flight as a back-up when one of the engine generators fails.
hope this helps.
regards Vincent
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We spell it "Auxiliary". I've also not heard of any that provide thrust that is used to power an aircraft. However, that does not mean to say that no thrust is generated - I'm sure it is, it's just that it's so relatively small it is of no consequence.
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Originally Posted by Piltdown Man
We spell it "Auxiliary". I've also not heard of any that provide thrust that is used to power an aircraft. However, that does not mean to say that no thrust is generated - I'm sure it is, it's just that it's so relatively small it is of no consequence.
I believe its like a car's exhaust, any "propulsion" coming from the APU is just exhaust, the inlet of air is important to gain the power from the movement of the turbine.
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Probably not relevant to the question asked, but didn't the Trident (late model) have a "plastic engine" in the tail to provise thrust just for take-off? (as well as the usual APU) Or is that "Snopes"?
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Originally Posted by ExSimGuy
Probably not relevant to the question asked, but didn't the Trident (late model) have a "plastic engine" in the tail to provise thrust just for take-off? (as well as the usual APU) Or is that "Snopes"?
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They certainly did. The engine was a bit binary though: On & "Full Welly" or Off. Apparenty, following a rejected takeoff, this thing was still going full tilt. It was somebody's job to remember to turn it off after such an event.
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Originally Posted by ExSimGuy
[COLOR=blue] "plastic engine" in the tail ]
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I know this thread has been a bit on the humorous (humourous??) side, but my recollection is that the 747-200 actually took a bit of credit for TO performance on the APU, and if APU were not operating there was a slight (250kg???) penalty.
Not sure if that applied to other 747's.
Not sure if that applied to other 747's.
