kitplane01
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A321 Stretch and Rotation Angle

Thu Jul 13, 2017 7:31 pm

How much could one stretch the A321 before rotation angle became constrained?

The 737-10 added a 40" plug in the front, and a 26" plug behind the wing. How much could the A321 front-load the stretch like the 737-10 before weight-balance problems?
 
inferno
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Re: A321 Stretch and Rotation Angle

Thu Jul 13, 2017 8:20 pm

The MAX 10 is still smaller than the A321 but further stretching is a bit (no pun intended) of a stretch. Her wings are too small and it will compromise a lot of things like payload, range and field performance making it an unattractive product. If Airbus intends to stretch the A321, new wings and engines are necessary. And if they're designing a new wing anyway, might as well put taller gears and maybe ones with double bogeys.
 
N353SK
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Re: A321 Stretch and Rotation Angle

Thu Jul 13, 2017 8:31 pm

The A321 will tail strike at a pitch angle of 9.5 degrees with the struts fully compressed (i.e. hard landing). Not sure how that compares to 737-900.
 
Varsity1
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Re: A321 Stretch and Rotation Angle

Thu Jul 13, 2017 8:54 pm

The A321 is already rotation sensitive. Most stretches are 773/738/739/764/A345/6 etc..

"constrained" is relatively subjective.
 
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Boeing778X
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Re: A321 Stretch and Rotation Angle

Thu Jul 13, 2017 9:11 pm

How hard would it be to make the landing gear taller? An A321 stretch would almost certainly require it, as well as a bigger wing.
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parapente
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Re: A321 Stretch and Rotation Angle

Thu Jul 13, 2017 9:34 pm

Thread starter.Very apostate question relative to the existing MLG.Airbus (along time ago) said a 322 was possible so I guess it is.
Re all the threads on 737.No lengthening existing gear is not simple hence the solution Boeing came up with.
The answer may be 'a small stretch' not very helpful I appreciate.2 franes either side perhaps?
 
inferno
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 5:24 am

N353SK wrote:
The A321 will tail strike at a pitch angle of 9.5 degrees with the struts fully compressed (i.e. hard landing). Not sure how that compares to 737-900.


Looks like most stretched aircraft go with 9.5/9.4 degrees with a notable exception of the ATR 72. Is there any regulations for this?
 
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TripleDelta
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 10:36 am

inferno wrote:
Looks like most stretched aircraft go with 9.5/9.4 degrees with a notable exception of the ATR 72.


It's not just the ATR - any long aircraft that stands low off the ground has the same problem. The Q400 will drag its tail along at 7.5 degrees on landing (on a firm touchdown when fully loaded) and around 8.5-9 on take-off. The RJ100 too will suffer a tailstrike at around 7 degrees on landing (6.9 if I remember correctly).
Last edited by TripleDelta on Fri Jul 14, 2017 11:03 am, edited 1 time in total.
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uta999
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 10:53 am

Could these extra long aircraft not simply be designed to lift off flat, like a B-52. Then rotate further once in positive rate of climb, at the gear up stage.
 
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Polot
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 11:07 am

uta999 wrote:
Could these extra long aircraft not simply be designed to lift off flat, like a B-52. Then rotate further once in positive rate of climb, at the gear up stage.

That requires a lot more speed and thus runway.
 
mjoelnir
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 12:01 pm

The A321 has a flat rotation angle and that poses the danger of tail strikes, but a lot of frames have that problem. The 737-800 is worse in regards rotation angle and the 737-900 much worse. So I assume a stretch of the A321 should be possible.
 
Newbiepilot
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 12:35 pm

mjoelnir wrote:
The A321 has a flat rotation angle and that poses the danger of tail strikes, but a lot of frames have that problem. The 737-800 is worse in regards rotation angle and the 737-900 much worse. So I assume a stretch of the A321 should be possible.


A 737-800 will have a tail strike at 11 degrees. How is that worse than an A321 in regards to rotation angle?
 
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 12:43 pm

kitplane01 wrote:
How much could one stretch the A321 before rotation angle became constrained?




This is a weird question without an answer. A stretched frame will reduce rotation angle, which will cause rotation speed to go up and thus increase takeoff and landing speeds. There is no magic number where it becomes constrained. It is a continuous spectrum for the most part when looking at stretches.

In a way the A321 is already constrained, but it has bigger flaps than the A320 so landing speeds aren't much faster and runway performance is similar. The double slotted flaps are beneficial. The 737-900 does not have a revised trailing edge flap system like the A321, so that is why the 737-900 has a bigger speed difference compared to the 737-800 than the A321 does relative to the A320. Boeing probably could have improved runway performance in the 737-10 and 737-9 by adding double slotted flaps, but they are heavy and increase drag, which increases fuel burn, so they compromised on runway performance. The A321 is pretty good for runway field performance.
 
flipdewaf
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 12:59 pm

Newbiepilot wrote:
mjoelnir wrote:
The A321 has a flat rotation angle and that poses the danger of tail strikes, but a lot of frames have that problem. The 737-800 is worse in regards rotation angle and the 737-900 much worse. So I assume a stretch of the A321 should be possible.


A 737-800 will have a tail strike at 11 degrees. How is that worse than an A321 in regards to rotation angle?

I think that mjoelnir was thinking about the implication of the high lift system on the A321 which significantly alters the zero lift angle of incidence and so has and effectively higher tail strike angle than would otherwise be the case.

Fred
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 1:09 pm

flipdewaf wrote:
Newbiepilot wrote:
mjoelnir wrote:
The A321 has a flat rotation angle and that poses the danger of tail strikes, but a lot of frames have that problem. The 737-800 is worse in regards rotation angle and the 737-900 much worse. So I assume a stretch of the A321 should be possible.


A 737-800 will have a tail strike at 11 degrees. How is that worse than an A321 in regards to rotation angle?

I think that mjoelnir was thinking about the implication of the high lift system on the A321 which significantly alters the zero lift angle of incidence and so has and effectively higher tail strike angle than would otherwise be the case.

Fred


Yes the double slotted flaps on the A321 reduce the rotation angle necessary. However the A321 is usually flying at higher weights than the A320, which increases need for lift so approach angles aren't that different. The 11 degrees on the 737-800 is higher than the 9.5 degrees on the A321. The 737-800 is capable of operating from a 4300ft runway and the A321 is not, so that is why I don't understand how Mjoelnir came to the conclusion that the 737-800 is worse in regards to rotation angle than the A321.
 
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Revelation
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 2:21 pm

Why does a question about A321 rotation angle have to become an A vs B willie waving contest?
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 2:24 pm

Revelation wrote:
Why does a question about A321 rotation angle have to become an A vs B willie waving contest?


Good point, there was no need for me to respond to a Mjoelnir.
 
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 2:25 pm

inferno wrote:
If Airbus intends to stretch the A321, new wings and engines are necessary. And if they're designing a new wing anyway, might as well put taller gears and maybe ones with double bogeys.

And perhaps ones long enough to accommodate an even newer new engine option.
Inspiration, move me brightly! Light the song with sense and color.
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Faced with mysteries dark and vast, statements just seem vain at last.
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 2:27 pm

Newbiepilot wrote:
Revelation wrote:
Why does a question about A321 rotation angle have to become an A vs B willie waving contest?


Good point, there was no need for me to respond to a Mjoelnir.


It was a general comment, not one aimed at your response.
Inspiration, move me brightly! Light the song with sense and color.
Hold away despair, more than this I will not ask.
Faced with mysteries dark and vast, statements just seem vain at last.
Some rise, some fall, some climb, to get to Terrapin!
 
mjoelnir
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 2:27 pm

Revelation wrote:
Why does a question about A321 rotation angle have to become an A vs B willie waving contest?


Because it is a comparison with known other frames and has relevance. You can leave your constant attacks at home, I am not your punching bag. If you have difficulties with facts than stop posting

Furthermore the topic author mentioned the 737
Last edited by mjoelnir on Fri Jul 14, 2017 2:47 pm, edited 1 time in total.
 
Mangs
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 2:32 pm

The 737-800 will tailstrike at 11* at T/O and 9,2* during landing. And the -900 at 10* and 8,3*.
 
TRENT1000TEN
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 2:32 pm

uta999 wrote:
Could these extra long aircraft not simply be designed to lift off flat, like a B-52. Then rotate further once in positive rate of climb, at the gear up stage.


That would get fun on a summer's day in Denver
 
mjoelnir
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 2:57 pm

Mangs wrote:
The 737-800 will tailstrike at 11* at T/O and 9,2* during landing. And the -900 at 10* and 8,3*.


The 9.5° for an A321 is at landing MLG fully compressed.

For you Newbiepilot, AFAIK is the takeoff run off an A321 at MTOW, sea level, ISA about 2,180 m and a 737-800 about 2,300 m and I did not talk about it first.
 
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 3:12 pm

Mangs wrote:
The 737-800 will tailstrike at 11* at T/O and 9,2* during landing. And the -900 at 10* and 8,3*.


Thank you. I found these numbers for comparison:

Takeoff/Landing
A319 15.5 / 13.9
A320 13.5 / 11.7
A321 11.2 / 9.7

http://www.smartcockpit.com/docs/Avoidi ... Airbus.pdf

The A321 is not the most limited airplane. 64% of tail strikes are on landing. That would mean a small stretch is probably workeable. A big stretch would require some type of gear modification.
 
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Polot
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 3:35 pm

mjoelnir wrote:
For you Newbiepilot, AFAIK is the takeoff run off an A321 at MTOW, sea level, ISA about 2,180 m and a 737-800 about 2,300 m and I did not talk about it first.

The A321 ACAP puts the A321 takeoff distance at (max possible, so 93.5 t) MTOW around 2,500 m. But it is incredibly vague (i.e. no info on what thrusts used). There are several places that say 2,180 m on the web, but it is not actually clear if that is actually at MTOW or what MTOW is used.
 
mjoelnir
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 4:28 pm

Polot wrote:
mjoelnir wrote:
For you Newbiepilot, AFAIK is the takeoff run off an A321 at MTOW, sea level, ISA about 2,180 m and a 737-800 about 2,300 m and I did not talk about it first.

The A321 ACAP puts the A321 takeoff distance at (max possible, so 93.5 t) MTOW around 2,500 m. But it is incredibly vague (i.e. no info on what thrusts used). There are several places that say 2,180 m on the web, but it is not actually clear if that is actually at MTOW or what MTOW is used.


It can well be that my number is from before the last MTOW increase and there are different engine versions and without and with sharklets. But at least the takeoff performance is in about the same range as a 737-800.

in regards to short field or hot and high there just was a discussion viewtopic.php?t=1366035
 
parapente
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 4:41 pm

A large stretch of an A321NEO will (as stated above) require a new MLG (and most likely engines) so in a real sense the question would disappear.To retain the existing MLG (can it go to circa 100T?) then the question is how much would/could a small stretch be without ruining t/o and landing performance criteria?
From what has been stated above the answer appears 'some' but really hard to 'know' without the data that Airbus would not share.Note since the A/c would be at max weight it maybe fuel constrained in any event thus reducing range quite appreciatively (I imagine).
 
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LA704
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Re: A321 Stretch and Rotation Angle

Fri Jul 14, 2017 5:09 pm

Somebody here to run numbers? I think a fuselage frame of the A320 series is 0,534m long. If we stretch 3 frames aft of the wing and 5 in front the plane would be 4,272m longer in total, 24-30 additional seats. What would the rotation angle look like?

Use an A321neoLR as baseline and sacrifice the range for the stretch, keep the MTOW and change as little as possible. IMHO a CASM-monster for routes up to 3000km.
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WIederling
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Re: A321 Stretch and Rotation Angle

Sun Jul 16, 2017 8:02 am

TripleDelta wrote:
The RJ100 too will suffer a tailstrike at around 7 degrees on landing (6.9 if I remember correctly).


The RJ100 ( actually the whole line of derivatives ) has no high lift leading edge devices.
extending the flaps thus changes the effective wing incidence.( See the pronounced nose down
landing attitude.) Demand for rotation leeway is thus reduced.
A321 with the double slotted flaps should show basically similar effects.
finally: a potential A322 would probably also get some work done on the high lift arrangement ?
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TripleDelta
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Re: A321 Stretch and Rotation Angle

Sun Jul 16, 2017 9:25 am

WIederling wrote:
The RJ100 ( actually the whole line of derivatives ) has no high lift leading edge devices.
extending the flaps thus changes the effective wing incidence.( See the pronounced nose down
landing attitude.) Demand for rotation leeway is thus reduced.


The Q400 and ATR-72 behave the same - and yet it is still comparatively easy to scrape the tail, especially in unstable conditions (as a number of tailstrike incidents on all three types attest).
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Bambel
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Re: A321 Stretch and Rotation Angle

Mon Jul 17, 2017 7:26 pm

Mangs wrote:
The A321 is not the most limited airplane. 64% of tail strikes are on landing. That would mean a small stretch is probably workeable. A big stretch would require some type of gear modification.


From the 737-100 to the -900 is huge step that in no way was part of the initial design. But B was able to make it work even with some limited runway performance. On the other hand the A321 was part of the idea in the first place so the landing gear was tall enough to make it work with rather low limitations. So i wonder why it would be so hard to further stretch this family?

A somewhat related question: For the A345/46 Airbus enlarged the wing AFAIK by inserting some "plugs" to make it longer while retaining the basic structure and MLG. Would it make sense to try the same on the A320 wing (for a stretch)?

b.

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