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This question is only regarding aircraft that seat more than about 100 people.

Are cargo holds pressurised these days, what is the situation?

Are only some pressurized, most, of every single one? Does it depend on the carrier, operating region or are there other variations that matter?

Related questions:

  • Are cargo holds heated?

  • Do they have lights? (Aren't some lit for animals?)

  • I've noticed random mentions of "some" of the sections being pressurised. Is this correct? It would seem to me that, if indeed, only some are pressurised then, of course, you absolutely could not rely on your luggage being in a pressurised area.

  • and what about Fedex-type cargo-only aircraft?

To be clear, I ask this question re "today" because I noticed when googling on this, there is a lot of information, but only old information (say, 10 yrs old plus). That is a recipe for confusion and urban myth, so the total facts from you experts would be great.

(Possibly, it would be difficult to secure accurate online references for this - my quick searching anyway only revealed patchy, out-of-date looking stuffs. Note for example, the Wikipedia article on Cabin Pressurization has only one poor, no-referenced sentence on the whole matter!)

Note for example... Spray bottles (pressurized) in the checked luggage?

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@Falster Welcome to Aviation SE! Of course, politeness is encouraged in both answering and asking questions, but just the occasional "thanks" to a good answer is sufficient :) –  shortstheory Aug 20 at 17:21
    
Lol good one shorts -- hey guys, I made this question, but I only then linked-through my usual SO account - but now I can't "tick" it unfortunately. If someone can sort of tick it on my behalf, go for it, cheers! –  Joe Blow Aug 21 at 13:15
    
(Heh I was just able to "vote up my own question!" whoo! :) ) –  Joe Blow Aug 21 at 13:15
    
I seemed to be able to hack it and tick the answer, thanks again gang. –  Fatster Aug 24 at 15:27

1 Answer 1

up vote 22 down vote accepted

Aircraft design has not changed that much in the last 10 years. In fact, most aircraft in production 10 years ago are still in production.

The cargo holds in typical airliners are indeed pressurized. Take a look at a cross section of an airliner (A380 here):

A380 Fuselage Cross Section

Notice the "egg" shape of the outer fuselage. This shape is very efficient at withstanding pressure. Because of that, everything within the fuselage shape is pressurized. This includes the cargo hold below. Only cargo holds located behind the aft pressure bulkhead would be unpressurized, and these are mainly found in smaller aircraft.

The floor of the passenger cabin is not designed to withstand that pressure. In fact, if the cargo hold depressurizes, the floor of the cabin can collapse, as in this incident (and because it wasn't addressed, this one too).

The fix for this was to allow for air to flow from the cabin into the cargo hold (or vice versa), so that pressure can equalize in the event of a rapid decompression.

Are cargo holds heated?

Sometimes. This will depend on the aircraft type. There are many threads over on the TechOps forums about this. The temperature can be adjusted depending on the cargo load.

Although the air outside the plane is cold, the walls are insulated (also for fire protection), and being pressurized along with the cabin helps too. Even in unheated cargo holds, the temperature should be above freezing.

Do they have lights? (Aren't some lit for animals?)

They do have lights, mainly for ground crew during loading and unloading. See this Boeing page about fire protection.

and what about Fedex-type cargo-only aircraft?

These aircraft are still based on the airliner models (and sometimes converted from airliners). Therefore, they have the same pressurization system. The cabin is still pressurized, or they would have to put in some type of bulkhead behind the cockpit.

This includes the cargo version of the 747 (both upper and lower areas are pressurized).

An exception would be an aircraft like the 747 LCF (Dreamlifter). The cargo section is not pressurized, and there is a bulkhead behind the flight deck section.

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I thought the accidents you link to were the reason why now the cabin floor must be able to withstand the pressure difference between a pressurized cabin and a vented cargo hold. FAR 25.365(e) requires any structure to withstand sudden depressurization loads. –  Peter Kämpf Aug 20 at 20:39
    
@PeterKämpf Thanks for looking at the FAR, that one is definitely relevant here. FAR 25.365(f) says "The pressure relief provided by intercompartment venting may also be considered." –  fooot Aug 20 at 20:48

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