Cargo doors for dedicated freighters - aft or fwd of the wing
 

What are some of the advantages/disadvantages of having a main deck cargo door aft or forward of the wing on freighters? I'm sure loading sequences is critical as weight and balance is constantly shifting during the process. Which configuration is faster to load? Also on a structural point of view, which needs more reinforcing? And which one is better in general?

Forward:

http://avherald.com/img/yakutia_b752...n_141206_1.jpg
https://previews.123rf.com/images/pr...tock-Photo.jpg

Aft:

https://i.ytimg.com/vi/wiMRbCyDONA/maxresdefault.jpg
https://abpic.co.uk/pictures/full_si...3343-large.jpg

Top, obviously.

https://eamonh.files.wordpress.com/2...hatch-load.jpg

Ideally - you'd want the door to be between the landing gear, so as to prevent the first pallet put in the door causing the tail (or nose) to flop on the ground.

But there are always complications. In the case of the 777F, putting the door (for a standard container size) ahead of the wing far enough to minimize risk of a loader running into the #1 engine would have put the door into the area where the fuselage is shrinking down to cockpit diameter.

So Boeing put it behind the wing (as close as possible).

The 777F and that Rear Cargo Door | Things With Wings

On a C-47 taildragger, behind the wing is a no-brainer: 1) away from the props, 2) lots more area, 3) closer to the ground, 4) between the main gear and tail wheel for solid balance.

https://www.army.mil/e2/c/-images/20...-14-152855.jpg

On stretched airframes, and especially tail-holers (727/MD-80 variants) - doors ahead of the wings are 1) safely between the gear, 2) in the largest (and often "only") available area, 3) away from the engines.

http://cargofacts.com/wp-content/upl...thcaption1.jpg

That West Air ATPF looks a bit tippy to me, but again - 1) away from props, 2) largest area - plus the forward weight of the engines may be sufficient counterweight, for a careful loadmaster using a calculator. ;)

Interesting breakdown of freighter door positions PIF.


However all Boeing built 747 freighters from the 200 to the 400/400ERF and on to the -8
have had nose loading doors and a rear door behind the wing as standard equipment

Yeah - you're right - I misread a source.... :( Deleted...

To make up for that - if your "cargo" might just be a passel of skydivers - a door ahead of the engines would be a bluddy BAD idea.

https://cdn.jetphotos.com/full/1/69924_1194717460.jpg

I'd say we load through the nose only about 10 percent of the time. You can't load tall pallets through the nose so you are giving up a lot of volume, it isolates the cockpit for a longer time and you need ramp space forward of the aircraft. That being said, I've seen a good crew unload from the nose while loading from the side to save turn around time.

Yes, in fact there's a sequence in the recent ITV documentary series on Heathrow showing a ground crew doing exactly that on a CargoLogicAir 747-400F.

On a forward cargo door freighter you wouldn't position the first pallets at the back right away right? Otherwise you tip the aircraft.

http://www.iasa-intl.com/folders/bel...MD11-Dubai.jpg

You would have to constantly be shifting the already loaded pallets as more pallets are being loaded.

Whereas, on on the aft cargo door freighters, the first pallets loaded are positioned straight to the front to secure the CG of the aircraft for the rest of the pallets to be loaded.

Wouldn't an aft cargo door setup save time this way? Or what am I missing?

BTW this question is about landing gear configurations like the 777 or A330 not taildraggers.

.. hence one uses tail stands while loading/unloading .. takes the worry out of the equation.

I have seen more instances of a misplaced tail stand going into the fuselage then the tail dipping due to CG.

That's the advantage of discipline and checklists. Flew F27, L188, B727 freighters over a lengthy period .. don't recall ever having a problem with tailstand discipline.

Then again, not enough discipline and the story changes ... as you observe .. not to mention the occasional departure with one still firmly attached ..

I bet this ground crew wish they had used that and some SA.
(6 slides)
https://www.slideshare.net/guestcad8...china-airlines

.. oh, dear.

Is that true of the dedicated -400F, built as such or just the ones that have been converted from the pax -400? I should know, having flown the dedicated -400F but it was a long time ago! I seem to remember there is a problem with pallet height, at the forward end, on the converted aircraft.

No converted -400 (or -200 or -300) have had the nose-door installed - that's only ever been an option on the production freighters.

As for height/width restrictions, the NCD offers a height of around 254cm, whereas the SCD has a height of 310. The NCD is also quite a bit narrower, at a minimum of 264cm vs 341 for the SCD. There's also height restriction all the way from the nose to behind the 'bump, with a max of 243cm vs 300cm in the remainder of the main-deck. Since the 'bump' on a converted -400 is quite a bit longer than on a production freighter, there are an additional 2 positions affected by the restriction.

Boeing didn't raise the cockpit on the factory freighters so both factory freighter and BCFs have a lower main deck ceiling towards the front. The upper deck is shorter on the factory freighters so more of the main deck can hold tall pallets/cans.

You can't load tall pallets through the nose so you are giving up a lot of volume

Then again, loading was a bit of a doddle on the Queen of the Skies.

(... exits, quietly, stage left ....)

Two doors for quick turn-around?
 

Not a good idea at all i suppose , for cost and structural reasons.

We can in the SLF ops do a much quicker turn with front and rear offloading and boarding onto apron. And lift-on wheelchairs front and back AND 20 minutes of fueling .
With airbridge, no way.
Is turnaround time as important with freight ops? It looks to me that a lot of large freighters are sitting idle.
We have from 06:00 until 24:00 to do our business, mostly.

Anyway , I am sure the loaders would find new way of tipping the Canoe!

One in front side, one behind wing, two loaders, incoming rear offload. New stuff, stuff it in front. Sounds simple, cant be.

I shall stick with SLF.
Happy Loading ( And Takeoff, Landing is the easy and fun part)

@ OP

maybe... the one that:
- has 2 crew ops
- burns least
- lifts more
- flies further

:)

Can there be any question?

https://s-media-cache-ak0.pinimg.com...1c8b182a41.jpg