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UA857
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Why do all new-build cargo aircraft have lower deck cargo areas?

Wed Mar 31, 2021 12:48 am

Why do all new build cargo aircraft have a lower deck cargo area? Shouldn´t cargo aircraft just have fuel tanks on the lower deck as most of the cargo is transported on the main deck? Wouldn´t the lower deck being just fuel tanks allow the aircraft to have TPAC/TATL range from the US west coast? Any thoughts to why cargo aircraft have lower deck cargo areas?
 
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TWA772LR
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Wed Mar 31, 2021 1:13 am

Why can't cargo aircraft carry more cargo?
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jetblueguy22
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Wed Mar 31, 2021 1:18 am

Because not all freighters need endless range? Especially for the integrators, having a lower deck protects them from going into another aircraft.

There is a strange obsession on this site with range. But there are very few flights that you need A330 range on a A320 airframe. Not to mention, making the lower deck all fuel tanks limits the money maker - actual cargo.
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fr8mech
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Wed Mar 31, 2021 1:18 am

UA857 wrote:
Any thoughts to why cargo aircraft have lower deck cargo areas?


Beyond the ridiculous cost of certifying and maintaining fuel tanks in the cargo compartment?

Because we carry cargo in the cargo compartments. We fill them up, just like we fill up the main deck.
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FGITD
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Wed Mar 31, 2021 3:12 am

UA857 wrote:
Any thoughts to why cargo aircraft have lower deck cargo areas?


Fuel is money out. Cargo is money in

Not to mention how much weight carrying all that fuel would add.

A 77F can carry 10 pallets on the lower deck, which I don’t have off the top of my head, but it’s not exactly a negligible amount of cargo.
 
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Starlionblue
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Wed Mar 31, 2021 4:45 am

UA857 wrote:
Why do all new build cargo aircraft have a lower deck cargo area? Shouldn´t cargo aircraft just have fuel tanks on the lower deck as most of the cargo is transported on the main deck? Wouldn´t the lower deck being just fuel tanks allow the aircraft to have TPAC/TATL range from the US west coast? Any thoughts to why cargo aircraft have lower deck cargo areas?


To summarise the above.

- Carrying more cargo makes more money flying further.
- Carrying fuel instead of cargo in the entire lower deck would probably be heavier, meaning beefing up structures.
- Cargo does not care about fuel stops.
- Certifying lower deck fuel would be more trouble than it is worth.
- Commonality with passenger variants.
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JayinKitsap
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Thu Apr 01, 2021 6:48 am

Nearly all low wing freighters have the wing box occupying the full height of the cargo hold. The floor is basically the lowest level that gets over the wing box. Nearly all commercial planes are cylinders or double bubble hulls to be efficient when pressurized. A lot of military aircraft that are not cylinders are not or minimally pressurized.

Just like the 777's carry a whole lot of cargo on passenger flights in the hold, that same amount is available with containers that are easy to load. Around 1/4 of the volume is below deck.
 
CanadianNorth
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Thu Apr 01, 2021 7:46 pm

Good question in theory, but in reality there is a few points here.

- Not all new build freighters have lower deck cargo space. Various Cessna products, ATRs, most military based transports, etc. all are being built without.

- Of the ones that do offer lower deck cargo, most are either based on or produced alongside an equivalent passenger model which has lower deck cargo space for all of the obvious reasons. It's far easier and cheaper to leave that lower deck as is than it would be to try and re-invent the wheel for a particular mark that will likely only sell a couple hundred copies at best.

- More cargo space means more cargo fits in the same airplane which means more income for the same cost which means more profit for the freight companies.

- Range is good up to a point, but there is a point where it becomes cheaper to make a fuel stop along the way than it is to try and lift enough fuel to go non stop.

- Many freight runs simply don't need the range, so no point in paying their share of designing, certifying, building and installing those 14 hour range belly tanks for an airplane that's just going to be doing two hour hops all day, and can just make a tech stop for the two times per year they actually want to go long haul with it.

- With a load of premium passengers on board many of them will pay a couple dollars more to go non-stop as they just want to get to the hotel at the other end for a hot shower and a cold beer. Freight on the other hand usually doesn't care if you make a quick fuel stop along the way. If you look at flights from Canada and the U.S.A. heading over to various points in Asia one quickly notices that the vast majority of passenger trips go non-stop, and the vast majority of freight runs stop in Anchorage. People just want to get there and don't care much about how many pallets of whatever are strapped in below them, but freight doesn't mind a quick pit stop if it means getting more packages per load.
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Weatherwatcher1
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Thu Apr 01, 2021 9:01 pm

E-Commerce has been resulting in lower density cargo. Freighters need all the volume that they can. While some freighters hit max takeoff weight before filling the cargo holds, it is pretty common to need all possible space.

Very few freighters go from the US West Coast to Europe. That’s not where the freight hubs are. Range isn’t that critical to freighters.
 
Redbellyguppy
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Fri Apr 02, 2021 10:46 pm

That cabin floor contributes a lot of structural integrity to the aircraft...
 
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CCA
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Re: Why do all new-build cargo aircraft have lower deck cargo areas?

Sun Apr 04, 2021 1:17 am

The 747 freighters rarely use the center fuel tank and would likely never be full if used. The only time it’s used is when it’s a very light cargo load and it’s the quickest way to get the aircraft back to home base. Cargo in the fuel tank would be a bonus ; )
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