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What factors defined the main deck cargo door location on freighter?

Posted: Thu Oct 29, 2020 7:51 am
by trent768
Just like the title says.

Take the 77F for example, there's some space in front of the wing to put the cargo door, yet they decided to put the door behind the wing. At first, I thought that it was because of balancing issues and to prevent the aircraft to tilting to the back during loading. However, they installed the 763F's cargo door in front of the wing, which is a bit weird since they (visually) have a similar "posture" to the 77F.

Even the tail heavy D10/M11 have their cargo door in front. If the balance issues was the main concern, wouldn't it made more sense for them to have a cargo door behind the wing?

Thanks!

Re: What factors defined the main deck cargo door location on freighter?

Posted: Thu Oct 29, 2020 5:55 pm
by Strebav8or
I believe the ideology of cargo loading has evolved over time. Whereas the DC-10 and 767, as you mention, have the door forward of the wing, currently thought is to load behind the wing, to the front, thus lowering the probability of standing the aircraft on the tail.
If you look the 747F has the main deck door at of the wing, also.

Re: What factors defined the main deck cargo door location on freighter?

Posted: Thu Oct 29, 2020 11:03 pm
by Florianopolis
I think behind the wing is preferred for CG concerns, but you have to have enough fuselage behind the wing for the deck loader and tugs and other equipment to have room to maneuver without banging into things like flap track fairings. A 777 has enough room; the DC10 might not. I think there's also an element of fleet consistency, so if all your airplanes have them in the same place, your ground handling operation and procedures may just make things easier if there's consistency.

Here's some pictures. Looks like the 767-300 might have room behind the wing, but they probably just use the same freighter door conversion as the -200, which probably doesn't have enough room. The DC10s and MD11s definitely don't have enough room back there.


Re: What factors defined the main deck cargo door location on freighter?

Posted: Fri Oct 30, 2020 7:35 am
by trent768
Florianopolis wrote:
I think behind the wing is preferred for CG concerns, but you have to have enough fuselage behind the wing for the deck loader and tugs and other equipment to have room to maneuver without banging into things like flap track fairings. A 777 has enough room; the DC10 might not. I think there's also an element of fleet consistency, so if all your airplanes have them in the same place, your ground handling operation and procedures may just make things easier if there's consistency.

Here's some pictures. Looks like the 767-300 might have room behind the wing, but they probably just use the same freighter door conversion as the -200, which probably doesn't have enough room. The DC10s and MD11s definitely don't have enough room back there.

Strebav8or wrote:
I believe the ideology of cargo loading has evolved over time. Whereas the DC-10 and 767, as you mention, have the door forward of the wing, currently thought is to load behind the wing, to the front, thus lowering the probability of standing the aircraft on the tail.
If you look the 747F has the main deck door at of the wing, also.

Thanks for the answer! Speaking of the 747F (the factory built one with the nose door), do they need some sort of special tail stand thing to prevent them from tilting when loading from the nose? Especially if they have their vertical tail tank loaded with fuel (if they are activated), looks pretty tail heavy in that situation.

Re: What factors defined the main deck cargo door location on freighter?

Posted: Fri Oct 30, 2020 8:39 am
by dcs921
Florianopolis wrote:
I think behind the wing is preferred for CG concerns, but you have to have enough fuselage behind the wing for the deck loader and tugs and other equipment to have room to maneuver without banging into things like flap track fairings. A 777 has enough room; the DC10 might not. I think there's also an element of fleet consistency, so if all your airplanes have them in the same place, your ground handling operation and procedures may just make things easier if there's consistency.

Here's some pictures. Looks like the 767-300 might have room behind the wing, but they probably just use the same freighter door conversion as the -200, which probably doesn't have enough room. The DC10s and MD11s definitely don't have enough room back there.


MD-11s do have enough room behind the wing for a main deck cargo door. McDonnell Douglas delivered 5 MD-11s from the factory with aft main deck cargo door. All 5 were built in a combi configuration and delivered to Alitalia. Alitalia converted all 5 into full freighters. 4 of 5 ended up at Centurion Air Cargo. McDonnell Douglas had so much room that the aft main deck cargo door was wider than the forward main deck cargo door. 160 inches wide for the aft door compared to 140 inches for the forward door.

Many years ago the company I work for used some of these MD-11s for a bit. The aft cargo door did help with CG issues during the load and unload process. The extra door width did create a bit of safety issue as the loaders we had could not span the entire door opening.

Re: What factors defined the main deck cargo door location on freighter?

Posted: Fri Oct 30, 2020 10:31 am
by trent768
dcs921 wrote:
Florianopolis wrote:
I think behind the wing is preferred for CG concerns, but you have to have enough fuselage behind the wing for the deck loader and tugs and other equipment to have room to maneuver without banging into things like flap track fairings. A 777 has enough room; the DC10 might not. I think there's also an element of fleet consistency, so if all your airplanes have them in the same place, your ground handling operation and procedures may just make things easier if there's consistency.

Here's some pictures. Looks like the 767-300 might have room behind the wing, but they probably just use the same freighter door conversion as the -200, which probably doesn't have enough room. The DC10s and MD11s definitely don't have enough room back there.


MD-11s do have enough room behind the wing for a main deck cargo door. McDonnell Douglas delivered 5 MD-11s from the factory with aft main deck cargo door. All 5 were built in a combi configuration and delivered to Alitalia. Alitalia converted all 5 into full freighters. 4 of 5 ended up at Centurion Air Cargo. McDonnell Douglas had so much room that the aft main deck cargo door was wider than the forward main deck cargo door. 160 inches wide for the aft door compared to 140 inches for the forward door.

Many years ago the company I work for used some of these MD-11s for a bit. The aft cargo door did help with CG issues during the load and unload process. The extra door width did create a bit of safety issue as the loaders we had could not span the entire door opening.

I KNEW IT!!! :D

I remember seeing pics of MD-11 with aft cargo door, but all the pics that I found on the internet are mostly FX birds with the front cargo door and I forgot who operated the one with aft door. I thought that I was imagining things. No wonder I didn't found one as they are pretty rare.

Thanks a lot dcs921!

Re: What factors defined the main deck cargo door location on freighter?

Posted: Sat Oct 31, 2020 1:43 pm
by Horstroad
trent768 wrote:
I KNEW IT!!! :D

I remember seeing pics of MD-11 with aft cargo door, but all the pics that I found on the internet are mostly FX birds with the front cargo door and I forgot who operated the one with aft door. I thought that I was imagining things. No wonder I didn't found one as they are pretty rare.

Thanks a lot dcs921!

Here you have one: :D


With the main cargo door in the aft, loading is easy. Put one pallet in, move it all the way forward, continue with the next one and repeat until the aircraft is full. Unloading in reverse.
With the door in the front, especially with an already tail heavy MD11, you have to load the lower fwd cargo compartment first, then you load the two positions fwd of the main deck cargo door, then you load one pallet after the other, but don't push it all the way aft but advance the whole stack aft one position at a time. Then at the end you can load the lower center cargo compartment.
I'm not a load master, but this is the general idea. You always need enough cargo in front of the tipping line to counteract the weight of the cargo in the aft.
You can't even use a tail stand like they do with the 747 as the MD11 does not have a jack fitting in the tail.

Re: What factors defined the main deck cargo door location on freighter?

Posted: Sat Oct 31, 2020 3:15 pm
by trent768
Horstroad wrote:
trent768 wrote:
I KNEW IT!!! :D

I remember seeing pics of MD-11 with aft cargo door, but all the pics that I found on the internet are mostly FX birds with the front cargo door and I forgot who operated the one with aft door. I thought that I was imagining things. No wonder I didn't found one as they are pretty rare.

Thanks a lot dcs921!

Here you have one: :D


With the main cargo door in the aft, loading is easy. Put one pallet in, move it all the way forward, continue with the next one and repeat until the aircraft is full. Unloading in reverse.
With the door in the front, especially with an already tail heavy MD11, you have to load the lower fwd cargo compartment first, then you load the two positions fwd of the main deck cargo door, then you load one pallet after the other, but don't push it all the way aft but advance the whole stack aft one position at a time. Then at the end you can load the lower center cargo compartment.
I'm not a load master, but this is the general idea. You always need enough cargo in front of the tipping line to counteract the weight of the cargo in the aft.
You can't even use a tail stand like they do with the 747 as the MD11 does not have a jack fitting in the tail.

Thanks, now I'm sure that I'm a little less crazy :D

Re: What factors defined the main deck cargo door location on freighter?

Posted: Fri Nov 06, 2020 4:55 pm
by HAWK21M
The most extreme CG location would be the determining factor to avoid Tail heaviness.
Also Loading/Unloading sequence from Bulk & Main Deck is important for safety purposes.

Re: What factors defined the main deck cargo door location on freighter?

Posted: Fri Nov 06, 2020 8:33 pm
by Florianopolis
dcs921 wrote:
Florianopolis wrote:
I think behind the wing is preferred for CG concerns, but you have to have enough fuselage behind the wing for the deck loader and tugs and other equipment to have room to maneuver without banging into things like flap track fairings. A 777 has enough room; the DC10 might not. I think there's also an element of fleet consistency, so if all your airplanes have them in the same place, your ground handling operation and procedures may just make things easier if there's consistency.

Here's some pictures. Looks like the 767-300 might have room behind the wing, but they probably just use the same freighter door conversion as the -200, which probably doesn't have enough room. The DC10s and MD11s definitely don't have enough room back there.


MD-11s do have enough room behind the wing for a main deck cargo door. McDonnell Douglas delivered 5 MD-11s from the factory with aft main deck cargo door. All 5 were built in a combi configuration and delivered to Alitalia. Alitalia converted all 5 into full freighters. 4 of 5 ended up at Centurion Air Cargo. McDonnell Douglas had so much room that the aft main deck cargo door was wider than the forward main deck cargo door. 160 inches wide for the aft door compared to 140 inches for the forward door.

Many years ago the company I work for used some of these MD-11s for a bit. The aft cargo door did help with CG issues during the load and unload process. The extra door width did create a bit of safety issue as the loaders we had could not span the entire door opening.


Wow, learn something every day. I wonder if the DC-10 didn’t have enough room for ground equipment to be comfortable