OT: Airliner air conditioning, I know someone here will know this... Options

[URY914]

On a car the a/c compressor runs off the engine.
In a house the a/c compressor is run by an electric motor.

(you can figure out my next question, can't you?)

How is the compressor on a airliner (737, 747,etc) powered?
I've never noticed a big v-belt on the engine before.

If it is powered by a electric motor, if so how is the generator powered? Is there some type of power take off from jet engines?

Thanks,

Paul

[2-OH!]

On the ground, air is bled off the APU (auxillary power unit - small jet engine) ducted into the heat exchangers and then fanned into the cabin...Once the engines are running, (APU off) air is bled off the 13th and 6th stages of the compressor (on each engine) then run through the heat exchangers and fanned into the cabin...The reason it's not so cool is because the bleed air is around 450 degrees and so it just cannot cool fast enough before it goes into the cabin...Ambient air also plays into the equation...The hotter the day, the hotter the bleed air, the longer it takes to cool it down...However, the air speed through the duct system is constant, so it does not get to linger or re-circulate through the exchangers again...

Once in the air, outside RAM air comes in to help and very quickly when you figure 35,000 feet is around 40 below 0...Also, the tube (airframe) becomes cooler instantly at that temp...

Except for the Concorde...That airplane growns 11.12 inches in flight due to heat expansion...Every flight...Remember, metal has memory...What happens to a paper clip after you bend it 100 times...

2-OH!