Is the A330F main deck cargo compartment pressurized? If not, what is the purpose of the structural cargo access door?

Question

I know there is a related question already asking if cargo holds in general are pressurized.

My question is specifically about the A330-243F in the below photograph. That looks like a pressure withstanding door/bulkhead dividing the fore crew compartment from the aft cargo compartment. Is that correct, and does it mean the aft cargo compartment is not pressurized? It's also possible both are pressurized and it's an airtight door for fire/fumes control.

Source

As mentioned in the linked question, it's likely both compartments are pressurized because of the efficient shape of the pressure vessel and so that the same pressurization system can be used across both passenger and cargo variants.

Answer 1

You're correct- for cargo aircraft derived from passenger planes, the cabin is pressurized. This reduces the complexity and certification requirements. Also, this allows for easy conversion too. The thick door may be due to two reasons:

• To improve load carrying/transferring capacity- airbus talks about

  ... the aircraft’s reinforced fuselage and doors, which increase shear and bending/running loads..

  also, the thick door will help protecting the crew should the cargo move forward in flight.

• To act like an airtight seal between the cabin and cockpit, so that it prevents smoke ingress into cockpit and to enable the crew to extinguish fire. FAA Class E (for cargo aircraft) requires isoaltion between the cargo compartment and cockpit.

Another thing to note is that even a number of military 'cargo' aircraft have pressurized cabins (An-124, I think is among exceptions), as they are also used in Medivac and causality evacuation roles- these require the cabin pressure to be set higher than normal.

Answer 2

The wall is a rigid barrier behind the supernumerary section that serves two purposes.

The first purpose is protect the supernumerary area and cockpit from cargo shifting forward during an accident. The barriers are rated to be able to hold back a full load of cargo at crash loads (9G*). This allows for the primary cargo securing system to only have to handle flight loads, making it lighter and less bulky, meaning more cargo can be carried.

The second purpose is to act as a smoke and air barrier. If a fire is detected in the cargo area, airflow to the compartment is shutoff. The rigid barrier then prevents smoke from crossing into the supernumerary/cockpit and keeps fresh air from crossing into the cargo area. Loss of fresh air should lead to the fire extinguishing, some aircraft will also depressurize the aircraft to extinguish a main deck fire. See 14 CFR 25.857 Paragraph (e).(4)-(5) (note that main deck cargo is a Class E cargo compartment).

The door is used to allow access to the cargo area during loading and during flight for various reasons. The door is not pressure rated.

*The crash landing loading of 9G is defined by 14 CFR 25.561. Although the FARs do not directly mandate that the barrier be used as crash barrier, it does mandate that the cargo subjected to 9G would not injure crew or block their egress path. Using a rigid barrier to react the crash loads is a design decision made to optimize cargo capacity.

Answer 3

In the good old days there was no wall, instead there was a net which was designed to prevent any loose load from coming into the galley/supernumerary seating area (commonly referred to as a G-net. There was also a smoke barrier which was affixed by velcro to the prevent any smoke from entering the aforementioned area.

Even the 747 combis had the net and smoke screen. The aft wall had no load restraint capabilities and apart from making things look nice it served as a form of insulation against cold and noise.

The net was not ideal as it could not prevent the movement of sharp/pointed objects as the lattice of the net was quite big, around 8-10 inches IIRC. So if you had a load of pipes or bars you had to have x number of compressible load ULDs (cargo which was of a certain density) which would act as the barrier to prevent the pipes/bars from going thru the g-net and into the galley/supernumerary seating area.

Certification requirements changed and I believe it is now mandatory for new build/newly converted to cargo aircraft to have a fixed bulkhead. This is not so much a pressurisation issue but more to prevent smoke and cargo from entering the galley/cockpit.