For example, what about the baggage compartment? Landing gear housing? Avionics?
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1$\begingroup$ Question for cargo compartments. $\endgroup$– foootAug 3, 2015 at 21:00
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$\begingroup$ @fooot, my question is more general, i.e. not asking only about cargo compartments. $\endgroup$– SparklerAug 4, 2015 at 18:04
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1$\begingroup$ Cockpit, yes!!! $\endgroup$– vasin1987Aug 4, 2015 at 18:33
1 Answer
Baggage, yes, landing gear, no.
The fuselage of an airliner is typically "capped" by two bulkheads, the forward and aft pressure bulkheads. These are roughly spherical sections that seal the central "cylinder" of the aircraft's fuselage.
Here's a 787's forward bulkhead:
... and a 767's aft pressure bulkhead:
Practically all the space in the fuselage itself between these two bulkheads is pressurized during high-altitude flight. This includes the baggage compartment.
Gear assemblies, however, are typically not pressurized. For some jets like the 737, this is fairly obvious:
Other designs with full doors for the gear assemblies aren't as obvious, but in general it's neither feasible nor desirable to pressurize the landing gear housings when airborne.
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1$\begingroup$ So basically everything inside the fuselage and between the two caps? $\endgroup$– SparklerAug 3, 2015 at 21:17
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$\begingroup$ Save for the L/G bays, yes. (This means that the holds are pressurized, and so are the avionics bays) $\endgroup$ Aug 3, 2015 at 23:51
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$\begingroup$ Not all the avionics, there is usually a radar array in the nose to provide TCAS and TAWS. $\endgroup$– KeithSAug 4, 2015 at 1:27
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1$\begingroup$ @KeithS, Neither TCAS nor TAWS uses a radar. TCAS uses an antenna since it is just a radio. TAWS is simply a database that is loaded into a display (often an FMS). The radar in the nose is simply for weather. $\endgroup$– Steve HAug 4, 2015 at 13:46
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1$\begingroup$ All the fuselage volume is at the same pressure because there is no separation between areas, for instance between the passenger cabin and the cargo holds. Circulation is facilitated by design and by regulation to protect the fuselage and prevent the cabin floor to collapse, particularly in case of explosive decompression. $\endgroup$– minsAug 4, 2015 at 23:37