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Advanced joined-wing designs

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posted on Jan, 28 2006 @ 03:46 PM
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Following Waynos’ proposal for the S-STOL (super-short take-off and landing) strike fighter, I have endeavored to research what are commonly called “Bi-diamond”, “joined wing” and “box-wing” configurations.

Combined wings, in the most basic sense, are not unlike bi-planes; two wings couple together. We are particularly interested in configurations which combine swept and forward-swept wings.

These types of configuration are increasingly popular although we have yet to see a production aircraft with them. They are however quite a recent idea: The earliest joined wing concept I could find were two essentially similar ones from 1986 by a forward thinking aviation student. His design centered on a novel twin fan VTOL arrangement and he makes scant mention of why he chose the joined wing:


Note that he places the leading wing lower and the aft wing higher –an arrangement which is consistent throughout my research. Waynos’ design however reverses this, which we hope will improve high angle of attack capability because the leading wing will not mask the rear one.



The best known combined-wing concept is probably Lockheed Martin’s future tanker/transport design featuring a box-wing:


Perceived advantages of this configuration are primarily that it can accommodate two refueling booms (on the wing tips) and marginal (?5%?) induced drag advantages. Another advantages cited around box-wing designs (i.e. wings joined by endplates, typically without dihedral) is that they offer good stability.

Generally speaking, good stability is not a desirable characteristic of a fighter though (opposite to agility, within reason).

Joined wings, where the wings meet on the same level and have a significant dihedral/anhedral component, are also popular. This NASA image of a joined wing plots the air pressure at high subsonic speeds (red= low, green= high).


Note the apparent almost equal lift from both surfaces –implying the potential to be extremely high lift designs. That could be translated into short-take-off and economic fight performance. It is not clear to me (uneducated moron…) whether this configuration has good slow speed performance (desirable for short landings) – the stall on the lead wing would start at the tips, where key control surfaces would be (bad news) and progress inwards, whereas the stall would start at the root of the rear forward-swept wing and travel outwards, leaving the outer control surfaces of the rear wing functioning at slower speeds. But surely the two wings interact ???.


Joined wings with distinct anherdal/dihedral (producing a diamond shape when viewed from the front) offer greater potential for maneuverability because the control surfaces could be used to push the aircraft sideways. Within certain maneuvers, this is considered super-agile. However they certainly aren’t the only configuration which allows for super-maneuverability.


(Illustration from www.airpower.maxwell.af.mil...)

Combined-wings in general also offer control surface redundancy which could be translated into better combat survivability, and potentially lighter wing structures for equivalent lift/area (the joining providing rigidity allows lighter construction).


An interesting variation on the combined-wing is Boeing’s “fluid wing” which combines a swept wing with a forward-swept wing but both are on the same plane.


The configuration is associated with the Sensorcraft UAV concept and the only advantage cited is that you can put AESA radar in the wings giving 360degree coverage.


Key supporting extracts:
Quoting Hanley Innovations www.hanleyinnovations.com...
______________________________
“….are claimed to exhibit the following favorable characteristics:
• Induced drag reductions
• Improved directional stability and control
• Improved static aeroelastic characteristics
• Light weight wing structure “

_______________________________


Quoting Col William D. Siuru, Jr., www.airpower.maxwell.af.mil...
________________________________
“The joined wing is another concept that could provide enhanced maneuverability (fig. 4). A joined-wing aircraft has its tail wing swept forward to be joined with the rearward swept main wing so that the wings form a diamond when viewed from the top or head-on. Besides providing a lighter, stiffer aircraft with decreased drag, this concept makes some interesting flight motions possible. To move sideways without rolling, the control surfaces on the front and rear wings could be deflected in unison to provide equal but canceling rolling movements. To make rapid pitch-up maneuvers, the front and rear surfaces could be deflected in opposing directions. Moving all surfaces downward results in lift augmentation that allows the aircraft to rise essentially vertically.”

____________________________________


Online Sources: www.aeromech.usyd.edu.au...
ksea.org...
www.aeromech.usyd.edu.au...
ad-www.larc.nasa.gov...
www.airpower.maxwell.af.mil...


[edit on 28-1-2006 by planeman]

[edit on 28-1-2006 by planeman]




posted on Jan, 28 2006 @ 06:28 PM
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See, I told you it was a good layout for high agility in the way I suggested it, but you wouldn't believe me!


But seriously, that is an excellent post planeman, I'm very impressed. However this layout does go back furhter than 1986. The Dornier 'Rautenflugel' (dunno if I've remebered that rigth) proposal for the TKF-90 requirement dates from 1978-79, maybe even earlier.



posted on Jan, 28 2006 @ 06:50 PM
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The Dornier Rautenflugel (rhombus wing???) was certainly a combined wing and a very interesting idea. my excuse for not including it is that neither wing was forward swept.


Where it does have similarities with our ideas is that it is the leading wing which is higher. also, it features a LERX.

Our mission is to find out WHY none of the other combined-wing designs we've found has the leading wing higher.

Also, re agility. That quote is the only place I've seen which suggests they are highly agile and it's only talking hypothetically -it also partially conflicts with many sources which say how stable boxed wings and joined-wings are.


also, here is a joined wing design flying from www.afrlhorizons.com...



Nice quote from sysd.org...
"Both front and back wings of VL scheme create almost the same lift, so CG is exactly at middle of them. I say "almost the same" because if it were same the airplane's natural behavior would be "climb until stall", and we want something that flies horizontally thus front wing has lower incidence and CG itself is a bit in front of middle point. "

I'm all for trying out the front wing higher config with flow dynamics software but maybe we should try out a low wing fist config as we really are going against the tide here......

[edit on 28-1-2006 by planeman]



posted on Jan, 28 2006 @ 07:39 PM
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Wouldn't the down draft from a higher leading edge wing interfear with the lower trailing wing in normal flight modes?

Having the trailing wing higher would only cause problems duering high angle of attack flights, a much less common flight regime than level flight.



posted on Jan, 28 2006 @ 09:16 PM
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Thats one of the questions that needs answering Dunc.

Planeman, I once read (a very long time ago) a source that was most likely Fliight, which stated that in such a theoretical design (theory was all there was back then) a lower forward wing was good for stable cruise conditions while a higher forward wing induced natural instability and enable high degrees of manouverability. The damn problem here is I cannot at all remeber WHY this is so
Thats why I was hoping our flow dynamics model would give us some answers.

One thing I have noticed though, look at the type of aircraft you have uncovered with low forward wings, there's a tanker, a private aircraft, basically planes where straight and level is a good thing. Considering that the only combat aircraft to use a similar layout, the Dornier, places the forward wing in the high position maybe this bears it out? Yes, I know it could also be a coincidence


[edit on 28-1-2006 by waynos]



posted on Jan, 28 2006 @ 11:48 PM
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Yeah I'd like to see this as an eats-1 concept... as soon as I get around to putting my own up.. I just haven't had the time yet



posted on Jan, 29 2006 @ 03:01 AM
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Great post planeman... I've always wondered about this wing types... Now I'am a bit smarter again...


[edit on 29-1-2006 by Figher Master FIN]



posted on Jan, 29 2006 @ 06:38 AM
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Another pic of the flying joined-wing demonstrator:

A key aspect of the Sensorcraft requirement is to have AESA as load-bearing structures, typically in the wing. That is the primary reason two out of the three proposal feature joined-wings of sorts (see also Boeing’s fluid wing above).

Here’s an older concept image of a joined wing Sensorcraft courtesy of Flight Int.:


Moving on to something more solid, here’s a NASA wind tunnel model:


Lastly in my research, Phoenix Navigation are pushing these joined wing UAV concepts:


______________________________________

Ok, thinking ahead to a test plan for our joined/box wing wind tunnel model:



Some of the tests can be skipped/modified depending on indications from previous tests.

I have put asymmetrical angles of incidence on the leading and rear wings because we hope to get slightly more lift from the rear one so as not to require trim for level flight.

The test plan concentrates on angle of attack performance because that’ll give us the clearest comparison with the FSW concept it’s in competition with.

I think the main difficulties are going to be:
1) Getting the models accurate enough to give meaningful results (no offense modelers)
2) Interpreting the fluid dynamics data
3) Any limitations with the free fluid dynamics software (Gerris looks best)

Any thoughts?



posted on Jan, 30 2006 @ 06:00 AM
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I don't know that much about joint wings! However, the configuration would suggest that such an aircraft would possess the advantages of both forward swept wings and traditional swept back wings. Is this technically correct?

Tim



posted on Jan, 30 2006 @ 09:39 AM
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Good question... I guess it would but It may be more like the saying jack of all trades master of none



posted on Jan, 30 2006 @ 01:21 PM
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Originally posted by ghost
I don't know that much about joint wings! However, the configuration would suggest that such an aircraft would possess the advantages of both forward swept wings and traditional swept back wings. Is this technically correct?

Tim
I am not schooled in this but I'd say yes and no. I would think (hope.... we'll find out) that it would have similiar low stalling speed of the FSW but not the good transonic drag advantage. I could be wrong though.



posted on Jan, 30 2006 @ 10:01 PM
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www.colabsystems.com... GOOD SURF


Have fun



posted on Jan, 30 2006 @ 10:03 PM
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one image from the web site :
www.colabsystems.com...[img]

www.colabsystems.com...[/img]



posted on Jan, 30 2006 @ 11:15 PM
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Are the last two posts nothing more than advertisements for the poster's business. Surely, that has to be against ATS rules.

The same person started another thread in this section with the same information.

[edit on 1/30/2006 by centurion1211]



posted on Jan, 31 2006 @ 02:39 AM
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Planeman,

>>
Following Waynos’ proposal for the S-STOL (super-short take-off and landing) strike fighter, I have endeavored to research what are commonly called “Bi-diamond”, “joined wing” and “box-wing” configurations.
>>

The big advantages of the joined wing concept lie in it's ability to vary aspect ratio independent of fuselage length/stiffness at 'the roots' and of course overall form/friction drag.

In /some/ designs, the wings cut the air at separate AOAs and thus allow you to design some pretty unique, 'paired', critical lift regions which do not require the massive energy losses of vortice lift (the chord being so small that it's really more penalty than gain in terms of structural flex).

>>
Combined wings, in the most basic sense, are not unlike bi-planes; two wings couple together. We are particularly interested in configurations which combine swept and forward-swept wings.
>>

I have looked at these as an alternative to a high aspect ratio flying wing in a VTOL application for a small ship launched, high speed, UAV. They offer some stability advantages IF you can make them 'variable geometry' to the extent that the wings either collapse like a scissor hinge or decouple to slide up an external fuselage (chine) track or groove for deckspot factored as well as potentially cruise-Mach reasons (I have also considered a rotary hinge for the fuselage itself).

The way I made mine, there was also a reasonable gain in propulsion efficiency by returning to an L+LC, dual-engine, configuration which effectively used microejector technology along the wings to maintain a constant low pressure (think hovercraft) 'lift curtain' around the two principle lift posts without an auxilliary roll duct system.

The forward engine essentially deactivates for cruise flight.

Given it was designed for a 'pure' ISR role, independent of landbased or big deck air, I still preferred to put the majority of the fuel in the wings and foreward/aft primary fuselage tanks while retaining the centerbody for a modular EO/Radar based sensor suite that employed a stressed composite (pressurizeable) conformal canoe radome along with endfire systems in the nose and tail.

Sizing an antenna suite to any particular bandwidth/dipole array functionality makes for difficulty in rewiring the system to other functional roles/look angles at a later time and also adds weight outboard where it doesn't need to be.

The 'hollow' of the centerwings in this case makes it simpler to get to the dorsal hatch cover of the center mounted avionics systems on a vibration dampened ready-raft set of fuselage beams that allows for the entire radar/EO head to be replaced as a single unit without further sealant required.

>>
These types of configuration are increasingly popular although we have yet to see a production aircraft with them. They are however quite a recent idea: The earliest joined wing concept I could find were two essentially similar ones from 1986 by a forward thinking aviation student. His design centered on a novel twin fan VTOL arrangement and he makes scant mention of why he chose the joined wing:



Note that he places the leading wing lower and the aft wing higher –an arrangement which is consistent throughout my research. Waynos’ design however reverses this, which we hope will improve high angle of attack capability because the leading wing will not mask the rear one.

>>

You don't want to 'pod up' the wing because it's stiffness:weight advantage lies in the way it does not have to carry-thru on a fuselage lapjoint or ringframe. I prefer slightly different wingsweeps for the forward and aft airfoils and a built in an/dihedral join differential that washes out to a common tipcontrol plane.

With care there isn't too much worry about shock migration or blanking off the lead airfoil but you don't want them to have aeroelastic or vibration harmonics in a common axis of motion or what bothers one will couple and harmonize to the other. The easiest way to assure that is to keep them from biting the same air.

>>
The best known combined-wing concept is probably Lockheed Martin’s future tanker/transport design featuring a box-wing:


Perceived advantages of this configuration are primarily that it can accommodate two refueling booms (on the wing tips) and marginal (?5%?) induced drag advantages. Another advantages cited around box-wing designs (i.e. wings joined by endplates, typically without dihedral) is that they offer good stability.

Generally speaking, good stability is not a desirable characteristic of a fighter though (opposite to agility, within reason).
>>

Good fighters are never seen to be engaged and the gutted-skate design with planform and vertical silouhette reduction does admirably at both. Great fighters have DIRCM which inhibits the effectiveness of 'dogfight' (as an exercise in agility dynamics) defined engagements by missiles. /Average/ fighters with good (sustained) EM performance can defeat 70% or more of all gunshots.

What else needs be said?

>>
Joined wings with distinct anherdal/dihedral (producing a diamond shape when viewed from the front) offer greater potential for maneuverability because the control surfaces could be used to push the aircraft sideways. Within certain maneuvers, this is considered super-agile. However they certainly aren’t the only configuration which allows for super-maneuverability.
>>

Stiffness at /weight/ defines the form by simplifying the amount of structural commitment to pylons and integral fuel cells and general twisting moment structural paths needing stringer/spar 'connective tissue' reinforcement.

However; those same things also limit the absolute loads inherent to having a nice, thick, root:tip taper and _lift_ inherent to a more conventionally skinned wing.

Now consider what you do when, even assuming the monkey-as-hood-ornament is gone, you have to stuff ALL your weapons system (12ftX3ft weapons carriage box), gas and sensor/propulsion weight into the primary fuselage. Even if it can be considered a pancake (Tomcat) equivalent lifting body, you lose most of your structural benefits by having to go back to some kind of a very wide root, probably mounted well aft of the nose.

Direct Sideforce/Liftforce aside, I would never put the joined wing in a fighter classification.

>>
Combined-wings in general also offer control surface redundancy which could be translated into better combat survivability, and potentially lighter wing structures for equivalent lift/area (the joining providing rigidity allows lighter construction).
>>

I think that survivability at least comes under the 'P-38s are harder to hit because they don't have a conventional fuselage centerline as aimpoint' category of too-drunk-to-be-scared talk. The joined wing cannot sustain /any/ damage to ANY of it's airfoil group without essentially destiffening the entire structural interlock. Since we are now dealing with missiles that throw out proximity fuzed fragment and blast kill mechanization on the order of a dozen times more total lethality than a WWII gun system, the reality remains pretty high, IMO, that you just _would not want_ to expose this aircraft to any kind of seriously strenuous as much as damage-intensive combat environment. Because you load a thin wing and then cut it at any given point, and it will fold completely. While there just would not be any 'field goal' (AC-119 over the Trail) type misses by something that came close enough to fuze.

What might be a little more interesting is the ability to couple and decouple descent rates and forward airspeed in the approach to a hover. Somewhat like a combination of the F-15 SMTD nozzle effect (speed brakes on the forward fuselage) and the F-14 DLC spoilers (tip controls). Something which should be a precondition of jetlift STOVL off of small decks without rotating the ejector cushion off of a level axis in achieving very 'repeatable' approach behaviors. In this, the hollow wing will likely have limited gust response and there are no tails so about the most you might need would be puffer nozzles at the joined tips.


KPl.



posted on Jan, 31 2006 @ 05:15 AM
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I welcome COLAB's input, without his "adverts" we wouldn't know about the Colab project which places the leading wing higher:

www.colabsystems.com...

Ch1466, the reason we wanted to 'pod' the join of the wings was:
1) to give vertical seperation
2) to make a wingtip hardpoint



posted on Jan, 31 2006 @ 05:41 AM
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Originally posted by ghost
I don't know that much about joint wings! However, the configuration would suggest that such an aircraft would possess the advantages of both forward swept wings and traditional swept back wings. Is this technically correct?

Tim


Alas, I would seriously doubt it.

I think that the Rearward Swept Wing would stall first while the FSW would not - inducing a real sharp nose down pitch. The problem being the setting angle of the two wings would be set for cruise, the 2nd wing being affected by the wake (downwash) of the 1st wing. I suppose, with LE slats, the problem could be reduced somewhat, but it would be quite complex.


As has been pointed out, forming a triangle out of the 2 wings and fuselage is great for structural reasons, as we all know a triangle is inherently strong, unlike a canti-levered beam (essentially what wings are at the moment). So the wing spar is greatly reduced in size, against this however is the 'in-plane' strength needed for the FSW.


As for compressibilty effects... I'd rather not think about it, big dirty wakes would present quite large problems I would imagine, as would the interaction of the supersonic bubble above the front wing in transonics with the rear wing - moving the 2nd wing below the first one would get around this somewhat, but a supersonic bubble would eventually emerge beneath the leading wing too.



posted on Feb, 1 2006 @ 08:36 AM
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Configuration of the triangulation of the wings as we have installed to the concept the best possible use in the very low ones gives speeds as in very high speeds. Stability is too extraordinary, at the time of piloting within the limits, and especially with unhooking. beach of centering is very large and makes it possible to determine ideal centering according to the style of plane which one wants to obtain... like air fighter, cargo plane, gliders, etc...The goal of the concept is to install it on apparatuses existing with a tiny and fast modification. The version gives also one great solidity with the type of the triangulation.
Then at the aerodynamic level, the saving in fuel is incredible, the penetration in the air is phenomenal.
Construction is easy and possibility of leaving them wings with the kilometers seen that they are identical, therefore costs of manufacture reduced to the maximum, and we are not at the end of our surprises after the wind tunnel tests, and flies from there....
For the anecdote the second flight the test pilot did not want to go down again more so much it was conquered by the revolutionary concept of these jointed wings.....
If partners want to launch out in the adventure, do not hesitate not with us to let it know, we are opened with all serious proposals....


HAVE FUN


P.S : Afflicted for my spoken English but I progress step by step, thank you for your comprehension



posted on Feb, 1 2006 @ 08:46 AM
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Colab, I'm fascinated by your project. I hope that it is successful.

If I may pick your brains, I wonder whether your experience of this configuration sheds any light on Kilcoo's concerns, particularly at stall speeds and transonic speeds. Have you considered how it would perform if the leading wing was much more swept than on your proposals?

Thanks for contributing.



PS. I'm sending you a private message U2U -you'll need to go to your mCentre (see icon on menu bar) to read it


[edit on 1-2-2006 by planeman]



posted on Feb, 1 2006 @ 08:21 PM
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PLANEMAN please did you recive my MCENTER reply ?






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