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Unpressurized/pressurized Areas In Aircraft  
User currently offlinePaco1980 From Belgium, joined Jan 2009, 21 posts, RR: 0
Posted (5 years 3 months 3 weeks 3 days 8 hours ago) and read 12787 times:

Hi All,

Quick question:

- What are exactly the areas that are not pressurized in the Aircraft? and what is the difference between the main manufacturers and Aircraft types?

From my understanding, in most of the cases:
- The Cockpit and Cabin are pressurized (fortunately!)
- All Cargo compartments are pressurized, I assume if any live animals are being transported, this would help...
- Bulk cargo??? not sure
- area between the outer skin of the fuselage and the cabin ceiling, not pressurized....
- Area between the outer skin of the Aircraft and the cargo compartment, not pressurized...
- Electronic area below cockpit: pressurized in case someone has to go through during flight?

Thanks for confirming if the above is correct...
Cheers,

Paco

18 replies: All unread, jump to last
 
User currently offlineFr8mech From United States of America, joined Sep 2005, 5340 posts, RR: 14
Reply 1, posted (5 years 3 months 3 weeks 3 days 7 hours ago) and read 12759 times:

In general:

Quoting Paco1980 (Thread starter):
Bulk cargo??? not sure

Bulk cargi is pressurized.

Quoting Paco1980 (Thread starter):
area between the outer skin of the fuselage and the cabin ceiling, not pressurized....

The fuselage skin makes up the pressure vessel. The area you describe is pressurized.

Quoting Paco1980 (Thread starter):
Area between the outer skin of the Aircraft and the cargo compartment, not pressurized...

See above.

Generally, the only areas of the aircraft that are not pressurized are the wheel wells, the area behind the cabin (from the pressure bulkhead, aft) and the area under the radome.

Again, the skin makes up the pressure vessel.



When seconds count...the police are minutes away. Never leave your cave without your club.
User currently offlineBMI727 From United States of America, joined Feb 2009, 15715 posts, RR: 26
Reply 2, posted (5 years 3 months 3 weeks 3 days 5 hours ago) and read 12709 times:



Quoting Fr8mech (Reply 1):
Generally, the only areas of the aircraft that are not pressurized are the wheel wells, the area behind the cabin (from the pressure bulkhead, aft) and the area under the radome

That's right. No matter what stories you hear about people suffocating in cargo holds it just doesn't happen. People can freeze to death in there, but they won't suffocate. That said, riding around in the hold is not a good idea.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineAcabgd From Serbia, joined Jul 2005, 659 posts, RR: 0
Reply 3, posted (5 years 3 months 3 weeks 2 days 23 hours ago) and read 12582 times:



Quoting BMI727 (Reply 2):
People can freeze to death in there, but they won't suffocate. That said, riding around in the hold is not a good idea.

in most modern airliners cargo holds are somewhat heated, in order to prevent liquids in passenger baggage from freezing.
Unless you are very sensitive to low temperatures and scantly clothed, you should be able to survive the flight in a cargo compartment without major trouble.

That, of course, doesn't mean you should really go out and try to do it  Smile



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User currently offlineSNAFlyboy From United States of America, joined Oct 2007, 86 posts, RR: 0
Reply 4, posted (5 years 3 months 3 weeks 2 days 22 hours ago) and read 12543 times:



Quoting Acabgd (Reply 3):
Unless you are very sensitive to low temperatures and scantly clothed, you should be able to survive the flight in a cargo compartment without major trouble.

If it started getting really bad, I'm sure you could find a shirt or two in someone's bag... Big grin

~SNAFlyboy


User currently offlineDALMD88 From United States of America, joined Jul 2000, 2533 posts, RR: 14
Reply 5, posted (5 years 3 months 3 weeks 2 days 21 hours ago) and read 12531 times:



Quoting Paco1980 (Thread starter):
- area between the outer skin of the fuselage and the cabin ceiling, not pressurized....
- Area between the outer skin of the Aircraft and the cargo compartment, not pressurized...
- Electronic area below cockpit: pressurized in case someone has to go through during flight?

The material the cabin interior panels are made from is like cardboard with a vinyl cover. The cargo bins are a little tougher. It is a hard fiberglass product that is air tight for smoke containment. Getting into the E/E compartment in some planes is easy, 767. There is a hatch you walk over near the L1 door. Others it is real tough, MD80/DC9. They have a real small hatch behind the captian's seat. On some it isn't at all possible, 757 or 737. There is no hatch at all from the cabin or cockpit.


User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 6, posted (5 years 3 months 3 weeks 2 days 21 hours ago) and read 12522 times:

The entire fuselage is pressurized from the forward pressure bulkhead.. normally where the radome is all the way back to the aft pressure bulkhead, normally where the tailcone attaches.


"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineCCA From Hong Kong, joined Oct 2002, 827 posts, RR: 14
Reply 7, posted (5 years 3 months 3 weeks 2 days 20 hours ago) and read 12500 times:



Quoting DALMD88 (Reply 5):
It is a hard fiberglass product that is air tight for smoke containment.

That's impossible as they would expand when the cabin pressure reduces during climb or have to be built to support them being pressurized, also they would all explode if the cabin had an explosive decompression.

So they may be sealed well, but certainly not airtight.



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User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 8, posted (5 years 3 months 3 weeks 2 days 19 hours ago) and read 12489 times:

The fuselage is pressurized from the fwd pressure

Quoting CCA (Reply 7):
That's impossible as they would expand when the cabin pressure reduces during climb or have to be built to support them being pressurized, also they would all explode if the cabin had an explosive decompression.

So they may be sealed well, but certainly not airtight.

You are correct they are not air tight.

Actually if the cargo liners were air tight the cargo compartment would be unpressurized, as the air enters the cargo compartment between the liner and the fuselage skin.

The liners main purpose is to act as a "fire block".


User currently offlineANITIX87 From United States of America, joined Mar 2005, 3299 posts, RR: 13
Reply 9, posted (5 years 3 months 3 weeks 2 days 19 hours ago) and read 12486 times:
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Can I ask a stupid question?

Is pressurization purely for passenger comfort? Or is it important for the air-frame's structural strength at those altitudes? I've always assumed it was the latter, but after reading some of the above statements and really thinking about it (the parts that are pressurized are actually at a HIGHER pressure than the outside, which adds stress to the airframe), I'm starting to think it's just for passenger comfort.

TIS



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User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 10, posted (5 years 3 months 3 weeks 2 days 18 hours ago) and read 12476 times:



Quoting ANITIX87 (Reply 9):
Is pressurization purely for passenger comfort?

Not only for passenger comfort but to keep them alive. If the cabin were not pressurized to an altitude were people can breath they would die. That is why there are breathing masks, in the invent of decompression.

Quoting ANITIX87 (Reply 9):
Or is it important for the air-frame's structural strength at those altitudes? I've always assumed it was the latter, but after reading some of the above statements and really thinking about it (the parts that are pressurized are actually at a HIGHER pressure than the outside, which adds stress to the airframe),

The effect of cabin pressure on the fuselage skins and bulkheads is not beneficial, in fact it is detrimental. Each time the fuselage is pressurized the air tries to expand the structure when the pressure is removed the structure returns to its original shape. Over a period of time this pressurizing and unpessurizing can cause cracks to form in the structure.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16992 posts, RR: 67
Reply 11, posted (5 years 3 months 3 weeks 2 days 7 hours ago) and read 12344 times:



Quoting 474218 (Reply 10):

Quoting ANITIX87 (Reply 9):
Or is it important for the air-frame's structural strength at those altitudes? I've always assumed it was the latter, but after reading some of the above statements and really thinking about it (the parts that are pressurized are actually at a HIGHER pressure than the outside, which adds stress to the airframe),

The effect of cabin pressure on the fuselage skins and bulkheads is not beneficial, in fact it is detrimental. Each time the fuselage is pressurized the air tries to expand the structure when the pressure is removed the structure returns to its original shape. Over a period of time this pressurizing and unpessurizing can cause cracks to form in the structure

Quite. This is why fatigue issue due to pressurization don't exist on, say, a DC-3. On a more modern airliner, however, the fuse ages faster.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineGLEN From Switzerland, joined Jun 2005, 221 posts, RR: 2
Reply 12, posted (5 years 3 months 3 weeks 2 days 1 hour ago) and read 12248 times:



Quoting EMBQA (Reply 6):
The entire fuselage is pressurized from the forward pressure bulkhead.. normally where the radome is all the way back to the aft pressure bulkhead, normally where the tailcone attaches.

except the wheel well (for nose and main gear)



"The horizon of many people is a circle with zero radius which they call their point of view." - Albert Einstein
User currently offlineDALMD88 From United States of America, joined Jul 2000, 2533 posts, RR: 14
Reply 13, posted (5 years 3 months 3 weeks 2 days ago) and read 12245 times:



Quoting CCA (Reply 7):
That's impossible as they would expand when the cabin pressure reduces during climb or have to be built to support them being pressurized, also they would all explode if the cabin had an explosive decompression.

So they may be sealed well, but certainly not airtight.

They are designed to be smoke tight. There are blow out panels for decompression and over pressure valves. While they may not be completly airtight like a navy sub, they are pretty tight, or they are supposed to be.


User currently offlineDocLightning From United States of America, joined Nov 2005, 19381 posts, RR: 58
Reply 14, posted (5 years 3 months 3 weeks 1 day 21 hours ago) and read 12189 times:



Quoting ANITIX87 (Reply 9):

Is pressurization purely for passenger comfort?

Actually, pressuring the cabin makes passengers MORE uncomfortable than not.

See, if you're alive (in a pressurized cabin) you can be uncomfortable in your 31" pitch Y-class seat with no IFE and a 6yo kicking you from behind. If they don't pressurize the cabin you will suffocate to death and then your corpse would freeze solid in the -50°C temperatures at cruise altitude. But corpses rarely complain of discomfort. Therefore, pressurization makes you less comfortable.

(Pardon my dark sense of humor)


User currently offlineMaverick623 From United States of America, joined Nov 2006, 5564 posts, RR: 6
Reply 15, posted (5 years 3 months 3 weeks 1 day 20 hours ago) and read 12178 times:



Quoting SNAFlyboy (Reply 4):
If it started getting really bad, I'm sure you could find a shirt or two in someone's bag...

It's happened before, and that's exactly what the guy did.



"PHX is Phoenix, PDX is the other city" -777Way
User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 11
Reply 16, posted (5 years 3 months 3 weeks 1 day 19 hours ago) and read 12163 times:

True statement?

We were trained on the CR7 to not put live animals in the forward baggage hold. Asside from the obvious resons of space, it was not heated life the aft baggage hold and the animal would die. Dry ice and pets-seperated. Dry ice in the front and pets in the back (as always) but never together.



What gets measured gets done.
User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 17, posted (5 years 3 months 3 weeks 1 day 19 hours ago) and read 12158 times:



Quoting Paco1980 (Thread starter):
- Electronic area below cockpit: pressurized in case someone has to go through during flight?

The only reason it is pressurized is because it just so happens to be inside the pressure vessel. Not to mention that area needs some serious air conditioning and ventilation.

I was fortunate enough to travel inside every bit and corner of a CO 777 during an MX tour. The latch for the EE bay is right by the L1 door (ala 767) and is quite large. I'd say at least 3ft+ square, so you can fit comfortably. Once you climb down the ladder (and you'd be surprised how long it is) you are greeted by a pretty large room with nothing but hundreds of black boxes and miles of cables. It really is reminiscent of a server room with many server racks. Also, from the avionics bay you can go through a passage that will take you to the cargo compartment.

You seriously can't appreciate the size of that beast until you're standing under it, or inside its crevices. Awesome experience.

Quoting DocLightning (Reply 14):
(Pardon my dark sense of humor)

Not to mention if they don't pressurize the release of rather fetid bodily gasses may ensue. Big grin


User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 18, posted (5 years 3 months 3 weeks 1 day 5 hours ago) and read 12057 times:

Most pressurized aircraft.....pressurized areas are between the Fwd & aft Bulkhead,excluding the Air condition access bays,Empennage compt aft of the rear pr bulkhead & Wheel wells.

Quoting ANITIX87 (Reply 9):
Is pressurization purely for passenger comfort? Or is it important for the air-frame's structural strength at those altitudes? I've always assumed it was the latter

Alternatively you need to provide O2 masks for all Pax above 8000ft.

Quoting Maverick623 (Reply 15):
It's happened before, and that's exactly what the guy did.

How did he get the lights to work.What type.

Bulk cargo is pressurised but can get cold at Altitudes.On Freighters the insulation blankets are removed for all areas except Flight deck [section 41] to reduce weight,so it can get really cold.

regds
MEL



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