QantasA332
Topic Author
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Are Cargo Holds Pressurized?

Mon Dec 22, 2003 8:02 am

I know this topic was discussed back in '01, but after finding the following online, I wanted a clear answer:

"I spoke with delta airlines...They have the option of pressurizing the
cargo hold
, in which case it stays at the same temperature as the
passenger compartment. This is done normally only in the case of live
animals." -- (an M.I.T. student, for an assignment, presumably)

This is what I had thought originally (that cargo holds usually aren't pressurized unless needed), but I was then told by some a.net forum-users that it is always pressurized. Can someone give me a conclusive answer? Thanks alot.

qantasA332
 
air2gxs
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RE: Are Cargo Holds Pressurized?

Mon Dec 22, 2003 8:42 am

All cargo holds on transport rated aircraft are pressurized. They aren't all heated. The option is usually to heat the hold. That is the limiting factor as to whether the hold can carry live animals.
 
L-188
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RE: Are Cargo Holds Pressurized?

Mon Dec 22, 2003 12:09 pm

The outer skin is generally the pressure skin, so any hold within that skin will be pressurized.

There have been exceptions, for example, the AN-12,which was originally built as a military aircraft doesn't have a pressurized cargo compartment, and the nose lockers on a Fairchild Metro likewise forward of the forward bulkhead.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
SlamClick
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RE: Are Cargo Holds Pressurized?

Tue Dec 23, 2003 6:27 am

Most jet transports specify a bag pit for live animals. Presumably the other one is for dead animals. Sure seems to work out that way.

An "unheated" cargo bin is not completely unheated. It is pressurized with the same pack output as the passenger cabin. In some cases, avionics cooling discharge is ported through the cargo bins, then overboard. Except on very long haul ops I'd expect the "unheated" bin to stay habitable for the entire flight.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
QantasA332
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RE: Are Cargo Holds Pressurized?

Tue Dec 23, 2003 7:42 am

Thanks guys. I felt kinda stupid not knowing this, so the explanations really helped.

qantasA332
 
IMissPiedmont
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RE: Are Cargo Holds Pressurized?

Tue Dec 23, 2003 2:19 pm

And why, QantasA332, would you feel "stupid" for asking? You have no reason to whatsoever. It is a valid question which was correctly answered, sort of, above.

I''l let the "experts" answer why I say "sort of."
The day you stop learning is the day you should die.
 
QantasA332
Topic Author
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RE: Are Cargo Holds Pressurized?

Tue Dec 23, 2003 2:29 pm

Thanks, but I really should have known, being and aviation-nut and aspiring aerospace engineer/pilot...

qantasA332
 
IMissPiedmont
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RE: Are Cargo Holds Pressurized?

Tue Dec 23, 2003 3:10 pm

Should you then be able to tell me how to repair a 2 inch tear in the belly skin at FS 1214 of a 727? I doubt it. Shoot fire, I've done such repairs myownself and would not be able, without an SRM, to answer the question.

What you must learn right away, QantasA332, is to not ever apologize for asking a valid question. Never.

It's the day you do not ask because of that fear that you will be, pardon my language, screwed.
The day you stop learning is the day you should die.
 
QantasA332
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RE: Are Cargo Holds Pressurized?

Tue Dec 23, 2003 3:17 pm

Point taken. Thanks for that...

qantasA332
 
zak
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RE: Are Cargo Holds Pressurized?

Tue Dec 23, 2003 7:47 pm

regarding pressurized cargo holds:
2 months ago i spent 20 minutes discussing at the counter at EDDK with a 4U checkin lady that wanted me to take out some cans of beer from my luggage since they would "blow up" in the "cargo room" due to the lack of pressure which is also why they wouldnt transport pets(visited some friends in london that wanted some homegrown booze).
the plane in question was a A320.
sometimes i wonder where certain people get their instructions from. she did some phonecalls and then said that it was after all ok but i would have to be prepared to have blown cans and beer in my luggage.
sometimes i wonder if those people realize that cabinalt is usually not higher then normal roads in the alps. cabin alt on that flight didnt exceed 1900m(have an altimeter on my watch) and i actually took beercans to 4300m without them blowing. so even with a mild decompression and expedited descent to safe altitude one thing not to worry about is beer cans  Smile
10=2
 
SlamClick
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RE: Are Cargo Holds Pressurized?

Wed Dec 24, 2003 1:18 am

Without getting type-specific some air transports have a control in the cockpit for the a/c and pressurization systems, the use of which could stop the flow of pack air into a bag pit. This would result in a lowering of pressure and temperature in that pit. Hazardous to live animals for sure.

Zak

Opening the beer cans at 4300m would be a different matter. On the other hand with mild hypoxia you might be experiencing, the beer would be really effective.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
zak
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RE: Are Cargo Holds Pressurized?

Wed Dec 24, 2003 1:43 am

of course they have excess pressure, but they dont burst on their own  Smile
and you are spot on with the effectiveness of beer in high altitude  Smile
10=2
 
Dalmd88
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RE: Are Cargo Holds Pressurized?

Wed Dec 24, 2003 2:38 am

Slamclick, you have made me curious. Which types do have seperate pressurization controls for the bag pits? Heat I've seen but I've never come across one for pressure.
 
Guest

RE: Are Cargo Holds Pressurized?

Wed Dec 24, 2003 2:50 am

I have never "heard" of any transport airplane having "separate" cargo hold pressurization controls from the regular controls of cabin pressurization... The only difference is that some baggage areas may not be "heated" and are rather cold in cruise...
xxxx
In the 747, live animals are located in the forward hold, which is heated. However I know the heating/cooling system being quite ineffective. As an animal lover I would NEVER put a dog or a cat in a cage in any airline cargo hold... If you care for your pet - send it on cargo airplanes (non passenger flights) - where animals are always located on the "main deck" (generally on the forward pallet) with acceptable temperature and lights, not in a dark and noisy, freezing or overheated cargo hold of a passenger aircraft.
xxx
Happy contrails  Smile
(s) Skipper
 
SlamClick
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RE: Are Cargo Holds Pressurized?

Wed Dec 24, 2003 3:52 am

Guess I need to explain. I was not suggesting that airplanes would have one set of pressurization and climate controls for the cabin and another set for the bag pits. I was only saying that on some types there are switches associated with that system that will have an effect on the bag pit air. One that comes most readily to mind is on the MD-80. The RADIO RACK VENTURI switch in the FAN position in flight will close the venturi valve for radio rack cooling and forward cargo compartment heating. Makes the pit less puppy-friendly. There are probably other examples.

As a general thing, I like to keep my posts non-type-specific for several reasons.

  1. Many of the questions here are posed by people who do not have a million hours and thirty minutes in jet transports. There are many ways to solve the engineering problems of airliner design. Boeing, Douglas, Airbus, Lockheed, Fokker and many other all have different approaches, each of which may shed some light on the issue.


  2. I am presently type-rated in six different transports. In addition, I flew a couple others without getting the rating. Further, I taught groundschool on still others. When I do a new checkout I work very hard at forgetting the plane I am coming from. I seem to be pretty good at the forgetting thing.


  3. At the moment I am working off a laptop. I have manuals for all the planes I've flown or taught, and some I've never even ridden in, but they may be half a hemisphere away when I want to post something. If I can't back it up with a quote from the manual I'd rather not post.


  4. I'm fairly new to the plane I am flying right now and I'd rather not broadcast my ignorance too widely. Some of you will understand.



If someone would like a finer cut on my answer just ask. I try to get back to the threads after a while.

With highest regards for the true experts out there . . .

SlamClick




Happiness is not seeing another trite Ste. Maarten photo all week long.
 
FredT
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RE: Are Cargo Holds Pressurized?

Fri Dec 26, 2003 10:20 pm

You cannot have the cargo bay depressurised with the cabin pressurised. In fact, there are blow-out panels between the cabin and the cargo bays. Why? Since if there wasn't, and if there was a largish pressure hull breach in the cargo bay, the floor would collapse. It is not designed to withstand the pressure differential. You have a pressure hull and pressure bulkheads for a reason...

In fact, what the blowout panels are there to prevent has happened and resulted in a complete hull loss as the collapsing floor took the control cables with it.

Usually, the forward hold is heated while the aft hold isn't. Putting catering or live animals in the rear hold will result in burst bottles, frozen food and dead animals within short. Yes, it is pressurised using the same pressurisation source, but there is very little to no airflow through the hold to speak of, meaning it will soon be closer to outside temperature - 50 degrees centigrade below.

Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
L-188
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RE: Are Cargo Holds Pressurized?

Fri Dec 26, 2003 10:26 pm

I have heard of the "puppy snuffer" switch, Slamclick, but my understanding was that it controled heat not pressure.

Even on short flights those pits can get cold without additional heat.

When I had my new puppy sent out to me in the hold of the company 727, they forgot to tell the flight crew that there was a dog in the hold, so the puppy snuffer was in the off position for the flight (SOP for that company)

The flight consited of two 45 minute segments, but that was still enough to leave one cold puppy.
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MD11Engineer
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RE: Are Cargo Holds Pressurized?

Sat Dec 27, 2003 2:20 am

On most planes you can stop the flow of fresh air to the cargo holds to starve out a possible fire. That doesn´t mean that the cargo hold gets depressurized, you´re just not pumping fresh oxygen in. At the same time if you would use a cargo fire fighting system you´ll want to have the agent stay in the cargo hold and not get blown overboard. This, of course, would kill any animal in the cargo hold.

Jan
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User avatar
HAWK21M
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RE: Are Cargo Holds Pressurized?

Mon Feb 16, 2009 6:35 am



Quoting MD11Engineer (Reply 17):

On most planes you can stop the flow of fresh air to the cargo holds to starve out a possible fire.

Common in freighters.Reffered to as the Main cabin shut off valve.
regds
MEL
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boeing767mech
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RE: Are Cargo Holds Pressurized?

Mon Feb 16, 2009 2:50 pm



Quoting L-188 (Reply 2):
and the nose lockers on a Fairchild Metro likewise forward of the forward bulkhead.

The commuter I start out with it was common to have a cat or dog ice cube at least one or twice a month with new rampers putting live animals in the nose lockers.

David
Never under-estimate the predictably of stupidty
 
airbuster
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RE: Are Cargo Holds Pressurized?

Mon Feb 16, 2009 5:12 pm

I believe the An 124 and 225 only have the crew (upper) compartment pressurised....
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atlturbine
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RE: Are Cargo Holds Pressurized?

Tue Feb 17, 2009 2:09 am

QantasA332...check out this link to see what happens to the passenger cabin when a cargo door is not latched properly. In this case there were no sidewall vents to equalize the pressure ...there are several other examples similar to this...but you will get the idea. I hope this is helpful.

Mitch

http://en.wikipedia.org/wiki/American_Airlines_Flight_96
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