A doubt on cabin aircon

I've been on aircraft departing from Dubai during summer and wished I
wasn't before engine bleed air starts running the aircon, because for
some reason the cooling doesn't seem to have quite the same effect when
running from APU power, at least on the A3xxs.

Since this is certainly not something psychological, why was I feeling
uncomfortable? It isn't as if doors are kept open either, since
boarding is via airconditioned telescopic chutes, not ladders.

Ramapriya

wrote)
I've been on aircraft departing from Dubai during summer and wished I
wasn't before engine bleed air starts running the aircon, because for some
reason the cooling doesn't seem to have quite the same effect when running
from APU power, at least on the A3xxs.


In the USofA, we mostly call it "....the A/C."


Montblack
Thought that might interest you.

Montblack wrote:
wrote)
I've been on aircraft departing from Dubai during summer and wished I
wasn't before engine bleed air starts running the aircon, because for some
reason the cooling doesn't seem to have quite the same effect when running
from APU power, at least on the A3xxs.


In the USofA, we mostly call it "....the A/C."


Didn't use it to preclude inadvertent allusions to aircraft

Ramapriya

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


wrote in message
ups.com...
| I've been on aircraft departing from Dubai during summer
and wished I
| wasn't before engine bleed air starts running the aircon,
because for
| some reason the cooling doesn't seem to have quite the
same effect when
| running from APU power, at least on the A3xxs.
|
| Since this is certainly not something psychological, why
was I feeling
| uncomfortable? It isn't as if doors are kept open either,
since
| boarding is via airconditioned telescopic chutes, not
ladders.
|
| Ramapriya
|

"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

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
|
|

"Jim Macklin" wrote in message
news:_e%Ig.6303$SZ3.5545@dukeread04...
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.


I was actually thinking commercial flights (as was, I thought, the OP...)

They can get cabins down right frigid when they get the hose in early and if
the compressor is running well...

I've actually heard people ask the FA if they could turn the air DOWN in
July.

Jay B

"Jay Beckman" wrote in message
news:Ks%Ig.18236$RD.20@fed1read08...
|
| "Jim Macklin" wrote
in message
| news:_e%Ig.6303$SZ3.5545@dukeread04...
| 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.
|
|
| I was actually thinking commercial flights (as was, I
thought, the OP...)
|
| They can get cabins down right frigid when they get the
hose in early and if
| the compressor is running well...
|
| I've actually heard people ask the FA if they could turn
the air DOWN in
| July.
|
| Jay B
|
|

Sorry for the blank post...hit the wrong key. What I was
going to say was that the FBO probably won't roll out the
air machine for your 172, but the bizjets and King Airs use
them all the time. An example, a heat soaked Beechjet
baggage compartment will reach the NiCad battery limiting
temperature and cooling the battery should be done before
engine start.



--
James H. Macklin
ATP,CFI,A&P

"Jim Macklin" wrote
in message news:3_3Jg.6315$SZ3.3480@dukeread04...
|
| "Jay Beckman" wrote in message
| news:Ks%Ig.18236$RD.20@fed1read08...
||
|| "Jim Macklin"
wrote
| in message
|| news:_e%Ig.6303$SZ3.5545@dukeread04...
|| 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.
||
||
|| I was actually thinking commercial flights (as was, I
| thought, the OP...)
||
|| They can get cabins down right frigid when they get the
| hose in early and if
|| the compressor is running well...
||
|| I've actually heard people ask the FA if they could turn
| the air DOWN in
|| July.
||
|| Jay B
||
||
|
|

"Jim Macklin" wrote in message
news:194Jg.6321$SZ3.4639@dukeread04...
Sorry for the blank post...hit the wrong key. What I was
going to say was that the FBO probably won't roll out the
air machine for your 172, but the bizjets and King Airs use
them all the time. An example, a heat soaked Beechjet
baggage compartment will reach the NiCad battery limiting
temperature and cooling the battery should be done before
engine start.



--
James H. Macklin
ATP,CFI,A&P

Interesting...

I've experienced what our desert heat can do to car batteries...it ain't
good.

Jay B