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cosyr
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Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 2:34 pm

I'm sure that Boeing and Airbus sometimes just reluctantly put doors places because they need a certain capacity for evacuation, but why do they often prefer to put them behind the wings, like the 739ER, 707, DC-8 and as being discussed for the A321LR (which is what got me thinking about it.)

I realize that airlines today probably don't care about galley space around these secondary doors, and many probably don't use Door 2L on the 757 for boarding, but by putting the only secondary doors behind the wing, they eliminate that flexibility for airlines to have the option. Particularly on the A321LR, which would be used for Transatlantic flights, having a 2nd door help with boarding, separation of J cabins and prestige for the plane as so many even here complain about single aisle for long haul. Having the 2nd door removes at least one argument as to why widebodies are better for a 5 hour flight from BOS to DUB...

Is there a structural or safety reason that that door would not allow the same capacity if it was in front of overwing exits (like many 757's) as opposed to behind (as in the 739ER)? Or are airline actually requesting it this way for some reason?
 
lancelot07
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 2:51 pm

Quoting cosyr (Thread starter):

It is not only about capacity, distance is also limited and afaik you can't have seats in front of the most forward exit, and not behind the one at the back.
 
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Stitch
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 3:02 pm

Quoting cosyr (Thread starter):
Is there a structural or safety reason that that door would not allow the same capacity if it was in front of overwing exits (like many 757's) as opposed to behind (as in the 739ER)?

Structural should not matter. There are regulations on how far apart exit doors can be from each other, but on a frame like the A321 or 737-9(00), that is not an issue.

I expect the main reason to do it is customer (airline) preference. If you do not intend to use Door 2L for boarding, removing it in favor of overwing exits allows you to add more seats while still being within the certified Exit Limit. As the graphics you linked to note, removing Door 2 in favor of overwing exists increases capacity by 20.
 
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Polot
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 3:11 pm

Quoting Stitch (Reply 2):
As the graphics you linked to note, removing Door 2 in favor of overwing exists increases capacity by 20.

Well, 8 or so. Remember they are also applying Spaceflex galleys and it looks like they are squeezing a few more seats around Door 3.

I suspect Door 3 was shifted aft some to make the spacing between the overwing exits and doors better to squeeze in the most possible seats without wasted dead space for a lucky row or two.
 
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redzeppelin
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 3:24 pm

I don't know if this is a real design consideration, but I would add that legacy seating layouts put the highest seating density at the rear of the plane. As such, shifting the exits back does make a better configuration for evacuations, even if exits ahead of the wing would still be within regulations.
 
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cosyr
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 4:27 pm

Quoting Stitch (Reply 2):
removing Door 2 in favor of overwing exists increases capacity by 20

But wouldn't it do the same to replace door 3 with overwing exits and keep door 2 though?
 
32andBelow
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 4:38 pm

Quoting cosyr (Reply 5):
But wouldn't it do the same to replace door 3 with overwing exits and keep door 2 though?

You have to have a wing to have an overwing exit...
 
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Polot
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 4:48 pm

Quoting 32andBelow (Reply 6):
You have to have a wing to have an overwing exit...

He is saying instead of eliminating door 2 for overwings and keeping door 3 to instead eliminate door 3 for overwings and keep door 2.

There were probably spacing issues with doors 1 & 2 and the overwings that meant you could squeeze in another row by getting rid of 2 and slightly adjusting door 3.

Remember most premium/legacy carriers are likely to go for the standard door option. It is only the ones who want to squeeze in ~240 seats that will spring for the new door option (which remember, will likely cost extra $$$ especially as Boeing has no 240 seat narrowbody competitor).
 
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cosyr
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 5:02 pm

Quoting polot (Reply 7):
Remember most premium/legacy carriers are likely to go for the standard door option. It is only the ones who want to squeeze in ~240 seats that will spring for the new door option

Oh, I may have misunderstood. I didn't realize this new configuration was just an option. I thought they were proposing it as a mandated change, they way the 779 is going to mandate change to 8 doors from the current 10 on the 773/W...
 
Accidentally
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 5:08 pm

Quoting cosyr (Thread starter):
....and many probably don't use Door 2L on the 757 for boarding,

I just wanted to add...the majority of times I've flown the 757, we boarded via 2L.
Indianapolis, IN
 
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cosyr
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 5:23 pm

Quoting Accidentally (Reply 9):
the majority of times I've flown the 757, we boarded via 2L

Me too, on UA. I haven't flown the 757 on US, but since they had 2 seats there, I assume they don't use it regularly.
 
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Polot
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 5:46 pm

Quoting cosyr (Reply 8):
Oh, I may have misunderstood. I didn't realize this new configuration was just an option. I thought they were proposing it as a mandated change, they way the 779 is going to mandate change to 8 doors from the current 10 on the 773/W...

Yes, it is an option. As you can see the A321neo is still available with the old doors:


View Large View Medium
Click here for bigger photo!

Photo © Lars Hentschel



I do not know when the new door layout debuts.

As for boarding via 2L, while fairly common with the 757 it is extremely rare with the A321, at least with jet bridges. The 2L door is much closer to the engine on the A321 than the 757, so most airlines don't want to risk accidentally damaging the aircraft. I can't imagine the NEO, with its even larger engines, would change that.
 
N1120A
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 6:06 pm

This door configuration is really only needed where airlines want to max out seating on the A321. It is actually less efficient operationally.

Quoting polot (Reply 11):
As for boarding via 2L, while fairly common with the 757 it is extremely rare with the A321, at least with jet bridges. The 2L door is much closer to the engine on the A321 than the 757, so most airlines don't want to risk accidentally damaging the aircraft. I can't imagine the NEO, with its even larger engines, would change that.

And that is probably the biggest reason they went with this change.
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Jetmarc
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Fri Apr 15, 2016 11:57 pm

Does anyone know if they improved the engine clearance near the 2L/R doors on the A321neo for boarding? From some pictures, it looks like there may be more room.
"Sucka, I'm gonna send you out on Knuckle Airlines. Fist Class!!" ~ Mr. T
 
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caoimhin
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Sat Apr 16, 2016 12:01 am

Would human factors not be a consideration? In the event of evacuation, years of conditioning have given me the expectation that I can find an exit at the very front and very aft of the plane.
 
Jetmarc
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Sat Apr 16, 2016 12:53 am

I read that eliminating doors 2, it allows Airlines more flexibility in cabin configurations. They can add larger business class cabins that aren't hindered or made complex with 2L/R in the way, particularly when configurating for longer haul flights.

Aviation Weeking Article

"ACF gives Airbus and the airlines more flexibility to configure the cabin for long-haul requirements. Boeing 757s are operated with relatively small business-class cabins, because they typically end in front of door 2 to reduce complexity in the cabin.

However, in the case of the A321neo ACF layout, there is no more door 2 and larger premium cabins can be installed. The long-haul A321neo will also be equipped with movable bins that have been launched as an option earlier this year."
"Sucka, I'm gonna send you out on Knuckle Airlines. Fist Class!!" ~ Mr. T
 
FARmd90
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Sat Apr 16, 2016 2:36 am

How much money, time and effort would it cost Airbus to move the 2L door forward a few feet to allow boarding at that door? (How far forward would have to be minimum) Im sure a lot of airlines would love the added benefit. Wouldn't think it would be that hard since they moved the exits behind the wing back a little.
 
N1120A
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Sat Apr 16, 2016 3:50 am

Quoting jetmarc (Reply 15):
ACF gives Airbus and the airlines more flexibility to configure the cabin for long-haul requirements. Boeing 757s are operated with relatively small business-class cabins, because they typically end in front of door 2 to reduce complexity in the cabin.

LMAO. What? 757s have relatively large premium cabins.
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cosyr
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Sat Apr 16, 2016 1:22 pm

Quoting N1120A (Reply 17):
LMAO. What? 757s have relatively large premium cabins.

I think he was referring to lie flat Intl seating. Most only have 16 which is pretty low even for thin routes. But I suppose that is the problem with the 757. It limits how few seats you can have in J, but for domestic F it has always encouraged airlines to have more than they would otherwise at 24. Some airlines could remove galleys and lava at door 2 and make it easier to put the divider between F and Y where they want, but obviously more investment.
 
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LTU932
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RE: Why Aft Doors Rather Than 2nd Forward Doors?

Sat Apr 16, 2016 1:52 pm

Quoting polot (Reply 11):
As for boarding via 2L, while fairly common with the 757 it is extremely rare with the A321, at least with jet bridges. The 2L door is much closer to the engine on the A321 than the 757, so most airlines don't want to risk accidentally damaging the aircraft.

Last time I flew LH out of FRA, both jetbridges at our gate connected with doors L1 and L2 and boarding was via both doors. Don't know if LH still practices it in FRA and if this also done in MUC, I do know that in HAM, they always board the A321 via L1 (though HAM doesn't have dual jetbriges anyway).
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