Are cargo holds pressurised these days?

Question

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it would be difficult to secure accurate online references for this - my quick searching anyway only revealed patchy, out-of-date looking stuffs.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?

Answer 1

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):

The round shape of the fuselage outline 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, because the flat surface would need to be much heavier to do so. Decompression events are considered by regulations though, so there are vents that allow the pressure to equalize. In older aircraft without these vents, a decompression event can cause the floor of the cabin to collapse, as in this incident (and because it wasn't addressed, this one too).

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. For example, the cargo bay of a 767 stays above 7˚C but with heat stays above 18˚C.

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 where it mentions that "another safety feature on many newer airplane models prevents the cargo lights from operating in flight".

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).

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

Answer 2

Logically speaking, all cargo holds must be pressurized unless the aircraft flies below 10,000 feet or the type of cargo is restricted to no liquids, and no pressurized liquids like aftershaves, shampoos, medicines etc.

At higher altitudes the atmospheric pressure drops and if the cargo hold was unpressurized, all such bottles would burst causing possible damage to the cargo and/or aircraft.

Answer 3

Yes, they are pressurized and climate controlled, especially on commercial flights where live cargo eg pets, bees, chicks, etc may be loaded aboard in the spaces and would be lethal to the creatures to be in a space at subzero temperatures and without supplemental oxygen encountered during cruise at high altitudes.