737 air conditioner question

[sky-738]

hi,everybody.
as we all know that 737NG use ram air for bleed air cool for air conditioner use .but my question is when a very hot day on ground ,as we use APU for air,it still can provide very cold air to make us feel comfortable.
my question is ,at that situation , ram air is very hot , so what is the cold air source and how could APU make air cool.

[slam525i]

Air cycle machine - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Air_cycle_machine)

[sky-738]

slam,
that is exactly what i want to know.

[BOAC]

Have you done ANY groundschool course on the 737?

[ACMS]

Obviously not!! :D

[BOAC]

Wonder what his type rating looks like....................

[slam525i]

I was going to say "Lay off guys, it's just an interested person who doesn't know how packs work. If we all have this attitude, it's little wonder why young people aren't interested in aviation."

Then I clicked on his profile...

You might want to clear that up on your profile, sky-738. If you're just starting the ground school, or if you're a flight-sim pilot, it's okay! I don't mind. Just don't confuse people into thinking you have a B737 type rating.

[BOAC]

Correct, slam, and I'm sure most, like me, click on 'profile' to try and assess the level of reply. When we see "Current a/c Type 737" you realise the poster is a Walt. I suppose the the rating could have been done in exchange for smelly folding drinking vouchers in a back street 'enterprise', but.....................

Unfortunately the current modding ?'policy'? encourages these posters across the forum.

OP could,of course, come back and explain the puzzle and perhaps we could change our minds, but I suspect not?

[glendalegoon]

Yes, it is very suspicious that someone is asking questions about the AC system and has a type rating.

I've seen real pilots called not pilots for expressing their views.

Disagreement is fine.

But when mods do nothing about someone claiming to be a type rated pilot not knowing a fundamental system of a plane, that does make one wonder.

There are forums here to answer questions.

I remember many years ago a fine, fun looking man came up to me and admired the plane. He told me that he was a railroad engineer (this means the guy who drives the train locomotive in the USA). I said that was so cool and that the F3 Locomotive sort of looked like the front of our plane.

He smiled and then asked a question that only an engineer (railroad) could ask. He said: how do you get the power to the traction wheels?

I smiled and said: It isn't that way. Just imagine it is a shopping cart and you push it around and the jet engines do the pushing. He smiled and nodded.

That is a fine question from a railroad engineer. But if he told me he was type rated in my plane< i think I would call the FAA!

[172_driver]

It's been a while since I opened an FAA Commercial study book, but I am not sure if they describe the Air Cycle Machine in detail. The JAA books goes a bit more in depth but without a good teacher a student may not make much sense of, if they're not theoretically minded. More and more JAA theory courses are done as distance courses as well. Self-studies and internet based tests. Classroom hours are cut to make your license cheaper!!

If sky-738 is a real pilot, to me it sounds like one who never really joined the dots and got the big picture. I am not surprised if he's a product of the Indian/Chinese sausage machine trained in the US. 150 hours, I believe, the Commercial Ground School course was where I worked. Question banks readily available to ace the exams.



as we all know that 737NG use ram air for bleed air cool for air conditioner use

sky-738 seem to believe ram air cools the bleed air as means of air conditioning?

my question is ,at that situation , ram air is very hot , so what is the cold air source and how could APU make air cool

I think sky-738 meant to say "bleed air is very hot" and wonders how we can cool the bleed air while stationary on the ground an no air is flowing over the heat exchangers?



The system knowledge is so off the mark that the question is not possible to answer. But don't go to hard on sky-738. He's a victim of the system.

[Amadis of Gaul]

I don't know how reasonable it is to expect there not to be posers on a forum where members are not screened. Furthermore, from what I can tell, the mods aren't terribly interested in forum "purity" as it were, they seem more concerned with decorum. Their prerogative, I suppose.

[tdracer]

To be fair to the OP, I think a lot of the engineers at Boeing don't really understand how a pack works (and I fear that extends to some of those in the ECS group), even my understanding of the workings is pretty rudimentary. I once heard a Boeing engineer - when it was explained how the pack worked - say that it sounded too much like a perpetual motion machine :sad:

[Tinwacker]

Sky, for your information I suggest some further in-depth reading of the airconditioning system and how it operates to cool and warm the cabin.
Unfortunately in the info given through Wilkipedia at #2 there are a few basic mistakes so don't take it all as gospel....just as an introduction..

[dash6]

Even if you know how it works it's still magic!

[Amadis of Gaul]

The proper term is PFM.

[Tinwacker]

Stator Vane
Was this a trim air valve failed in the closed position ???
Always interesting to know...