For example, what about the baggage compartment? Landing gear housing? Avionics?

  • 1
    $\begingroup$ Question for cargo compartments. $\endgroup$
    – fooot
    Aug 3 '15 at 21:00
  • $\begingroup$ @fooot, my question is more general, i.e. not asking only about cargo compartments. $\endgroup$
    – Sparkler
    Aug 4 '15 at 18:04
  • 1
    $\begingroup$ Cockpit, yes!!! $\endgroup$
    – vasin1987
    Aug 4 '15 at 18:33

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:

enter image description here

... and a 767's aft pressure bulkhead:

enter image description here

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:

enter image description here

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.

  • 1
    $\begingroup$ So basically everything inside the fuselage and between the two caps? $\endgroup$
    – Sparkler
    Aug 3 '15 at 21:17
  • $\begingroup$ Save for the L/G bays, yes. (This means that the holds are pressurized, and so are the avionics bays) $\endgroup$ Aug 3 '15 at 23:51
  • $\begingroup$ Not all the avionics, there is usually a radar array in the nose to provide TCAS and TAWS. $\endgroup$
    – KeithS
    Aug 4 '15 at 1:27
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    $\begingroup$ @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 H
    Aug 4 '15 at 13:46
  • 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. $\endgroup$
    – mins
    Aug 4 '15 at 23:37

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