re:aircraft airconditioning

[LincTex]

All airliners basicly use a freon sytem (seldom) or "air
cycle" packs. (common)

Air packs are simple and light, but use a LOT of fuel to operate.
Freon systems are MUCH heavier and more complex, but more efficient.

[John Kunkel]

"LincTex" > wrote in message
...
> All airliners basicly use a freon sytem (seldom) or "air
> cycle" packs. (common)
>
> Air packs are simple and light, but use a LOT of fuel to operate.

The air packs only consume fuel when the APU is used as an air source, in
flight the engine bleed air is the air source and uses very little if any
extra fuel.

[Scott Skylane]

John Kunkel wrote:

>
> The air packs only consume fuel when the APU is used as an air source, in
> flight the engine bleed air is the air source and uses very little if any
> extra fuel.
>
>
Not true about the lack of fuel use. In the B-727, the center engine
does not typically provide bleed air for the packs in flight, and burns
200-300 less pounds-per-hour in cruise than the pod engines.

Happy Flying!
Scott Skylane

[Stache]

LincTex wrote:
> All airliners basicly use a freon sytem (seldom) or "air
> cycle" packs. (common)
>
> Air packs are simple and light, but use a LOT of fuel to operate.
> Freon systems are MUCH heavier and more complex, but more efficient.

If you have been on a long flight several hours you will notice the
aircraft get very warm inside. This is because the bleed air is shut
off from the air packs to save fuel. Some airlines pay the pilots
additional salary if they save fuel. This is why many airlines don't
start all the engines until they are at the end of the taxiway. Fuel
is money bleed air costs fuel, cool air cost money.

Stache