A doubt on cabin aircon

The FBOs in Phoenix have portable air chillers they roll up
to the airplane to cool the cabin and even the baggage and
battery compartment. But it can get hot inside withy the
engines at ground idle.



"Jay Beckman" wrote in message
news:C1%Ig.18233$RD.12650@fed1read08...
| "Jim Macklin" wrote
in message
| news:n7XIg.6274$SZ3.3157@dukeread04...
| A/C on a jet runs from an air cycle machine using what
is
| called P3 bleed air. This is air that has been highly
| compressed but prior to the burner section of the
engine.
| The air is at 150 to 300 PSI and over 1,000 degrees F as
it
| leaves the engine just due to being pressurized. The
air
| cycle machine is used to cool and expand the compressed
air,
| to mix ambient air to gain volume and can discharge air
into
| the cabin at a temperature within the range of 30-120
| degrees. But the use of P3 air reduces engine power and
on
| really hot days [and nights] the crew will turn the P3
A/C
| bleed air off to maximize engine power.
| Aux power units are much smaller engines and they
produce
| enough power and bleed air to run a generator and supply
| bleed air to start the main engines. That is not
usually
| enough to fully run the A/C.
|
| www.boeing.com/commercial/cabinair/ecs.pdf
|
| In Phoenix, they stick a hose in a hole...
|
| Jay B
|
|