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Cry for technical help re foward swept wings

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posted on Jan, 9 2006 @ 08:22 AM
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The double wing (one downstream of the other) probably will not be quite as efficient as you would hope.

You have to ensure the 2nd wing is not masked by the forward wing at higher angles of attack, as you will not be getting any lift from it = useless.

However, in avoiding this, you mount it in the wake of the upstream wing in cruise - which leads to a drop in efficiency, probably quite significant, due to the reduced angle of attack caused by the downwash of the upstream wing (both from wing-tip vortices and from the bound vortex (also known as circulation).



I'll try to get time to have a good think about it this evening, and see what I come up with.




posted on Jan, 9 2006 @ 08:26 AM
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Originally posted by planeman
Guys, something –or rather someone, who interests me. Whilst trawling the net for “diamond wing” aircraft I found the page of a Mark Stock who has written a program to model airflow over wings. One of his pictures depicts a UCAV:

(image rehosted to preserve his bandwidth. Original context: mark.technolope.org... )
If only we had that capability.


It might be a pretty picture, but its a panel based method - so its pretty useless at higher AoA where seperation is an issue.



posted on Jan, 9 2006 @ 09:27 AM
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Waynos

I’ve put a vertical spacer between the wings on D-0014 (below). Although we can refine it further, I think this illustration will act as the main one before we go into the 3D modeling and (hopefully) ray-tracing (airflow analysis) stage.

Another more subtle refinement is that I’ve had the rear fuselage made fatter to allow more fuel. We could also consider a belly tray for even more fuel if the concern remains later in evaluation. Something that might not be apparent in this illustration is that I envisage all the necessary navigation and targeting devices to be built in rather than carried externally. The chin position is where the main targeting sensors/designators would be housed –such as straight off the Rafael Lightning pod or something.

We should definitely attempt to model twin weapons carriage at the wingtips if we can get some ray-tracing done.

Another problem I’ve just thought about is the position of the air intake for the lift jet –directly above the fuselage where it would be shadowed by the nose at high angles of attack. I propose that this could be overcome simply by having twin intakes ‘pop-up’ at 45 degrees from the same position (rather than a single door). This refinement would apply equally to all our designs.

Re the ‘full-diamond’ wing idea – I drew it with F-18 shaped main wing and canards –any comments on that? We need to put a ‘conventional’ wing design in the options package before comparative analysis.

As well as the S-STOL version we are coming up with, I’d also propose a STOL version for medium carries which have arrestor gear and catapults (or at least longer ski-jumps). The only major difference would be removal of the lift-jet –that would allow a significant increase in internal fuel –win-win. In that guise the conventional version would have even greater advantage over the bi-diamond and FSW versions (pity).



Kilcoo. Thanks for the pointers. Re the airflow analysis –is it pie in the sky to hope that we could realistically model these proposals in CAD or 3dMax and use free/open source programs to do credible (not up to industry standard necessarily, but not flawed) airflow analysis?



posted on Jan, 9 2006 @ 10:06 AM
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Originally posted by planeman
Kilcoo. Thanks for the pointers. Re the airflow analysis –is it pie in the sky to hope that we could realistically model these proposals in CAD or 3dMax and use free/open source programs to do credible (not up to industry standard necessarily, but not flawed) airflow analysis?


As long as you keep the angle of attacks low it should be fairly feasible and carefully used, could give some reasonable results. You maybe should look at comparing the results from your panel program to a real aircraft (benchmark it).

For the higher angle of attack stuff... well, if I can get enough free time I might be able to help there, but no promises



posted on Jan, 9 2006 @ 01:49 PM
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The ‘conventional’ design. I’ve clipped the diamond main wing to keep it within the 10m wingspan limits. To increase wing area I’ve removed the tip rails to the underwing.



posted on Jan, 10 2006 @ 06:26 AM
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Upon reading further I think the conventional wing brings with it too many penalies for this particular idea. An FSW is far superior in terms of lift, drag, agility, low stalling speed (thus much reduced approach speed).

After some thought I think that the Raspberry ripple FSW is my preferred design *unless* the split diamond we settled on can be shown to be superior. The benefits that appear obvious here for the bi-diamond would be greater internal fuel volume and greater structural integrity allowing for much more violent manouvering. If the layout can thus be shown to give high agility and without the drag penaly that was mentioned then that should take over as the preferred option IMHO, for me the conventional wing idea is a non starter as it adds structural weight (look at the inboard chord) and would require a bigger engine plus more fuel to attain the same flight performance as the FSW (according to the findings of the X-29 programme as noted in Jane's ATWA 1991).

Actually demonstrating the advantages or otherwise of these designs is something I cannot do however, anyone with the actual capability to do this is most welcome to take it on.

Thoughts?



posted on Jan, 10 2006 @ 11:07 AM
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Waynos,
I agree with your thoughts. The disadvantage for the pure-FSW as I see it is the limited number of stores stations it offers us. I’m reticent to add wingtip rails to it –although the loading is worst near the root so if we do have wing hardpoints, the tips are the best place for them.

The ‘conventional’ design would probably perform worst at S-STOL, being most reliant on the lift jet. But, unfortunately it’d be most suited to non-S-STOL operations, say from ‘medium’ carriers.

The next stage is 3d modeling and then airflow analysis. Will be interesting if we can get that far.



posted on Jan, 10 2006 @ 11:30 AM
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Regarding wing stations on an FSW design, here is a picture that shows Rockwell's thoughts during the Sabrebat design project.



I plan to use this layout with the addition of Typhoon style wingtip ECM pods on a model I intend to build of an X-29 based service fighter which I have christened the F-29A Scorpion, the missiles will be 2 ASRAAM outboard and 2 AMRAAM inboard.



posted on Jan, 11 2006 @ 09:52 AM
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Waynos, I’ve put the 3d modeling into another thread and had some good responses. I’ve also been looking into airflow modeling (Fluid Dynamics in techie speak) and have identified a couple of open source programs which may be useable. But they tend to need Mac or Linex operating systems etc. I’m in communication with one of the guys behind one of the projects which is a step in the right direction. Whether we’ll be able to do anything more than ‘basic’ remains to be seen –but something is better than nothing.

On that subject I also had an interesting chat with one of my techie contacts about flow dynamics etc. He thinks that the only way we’d get useful data is to actually get a productive programmer interested and possibly aerospace academics… to write a bespoke program. –too much time IMO. He also suggested that we could use MS FlightSim# to ‘fly’ the aircraft but only if they were aerodynamically stable concepts –which they ain’t.

He then went off on his own operating concepts, some of which were interesting. His aeronautical experience is limited to Air Cadets and a couple of solo glider flights –where they used stall-landings. He suggested a controlled-crash landing… oxymoronic chap that he is. He observed that the most certain way to stop dead on an aircraft carrier is to fly into the side of it. Lol.

But he also wondered why with modern recoilless rifle technology, no one had put a 30mm turret on a rotary UAV with a fire control system resembling the Phalanx. Hovering at 5,000 it could shoot at anything that moved and even shoot down missiles fired at it… not perfect but an interesting thought anyway.

Back to our S-STOL idea –something I’ve been playing with but not posted before was some way of using the EJ-200 as both the main engine and lift engine –which would involve putting it in the extreme nose so that it exhausts approximately where the lift jet did. This would require a twin boom layout which is inherently heavy and eats into wingspan. It also makes the engine intake duct very short and means that the TVC can only be 2d (up down). So a crap idea.



posted on Jan, 11 2006 @ 10:48 AM
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Maybe, maybe not. What is the t/o weight of our project? I think it may be too heavy for what I have in mind (prompted by your picture, above).

I don't understand why the engine would need to be quite so far forward? Maybe I misunderstand you, but my immediate thought here was, could the engine be mounted a little further back, right on the c.g, and pivoted in the middle so that it could blast straight down on the c'g of the aircraft? The you could dispense with the vanes completely and use a conventional convegent/divergent nozzle. This would then allow the thrust line to be diverted from the horizontal to a little beyond the vertical for thrust reversal on the ground. Here you are completely dispensing with thrust vectoring equipment and a lift engine with a conventional but pivoted engine.

It is similar in concept to the BAe P.103 tilt-engine fighter but with a small single engined UCAV instead. Probably quite achievable if only the engine is powerful enough. This may even work for V/stol (but probably not)


Following through the only way I can think of to achieve this is to use your twin boom layout but mount the engine, separately cowled, between the booms with a pivot line towards the rear of the engine to allow sufficient ground clearance when in the vertical position. Its a bit off the wall but something to think about.


He observed that the most certain way to stop dead on an aircraft carrier is to fly into the side of it. Lol.



excellent.



posted on Jan, 11 2006 @ 10:58 AM
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Waynos, great minds must think alike –lol. You ain’t gonna believe this but you’ve hit close to a previous concept the A.TT where thinking on before –D-0009/10 – tilt-fan STOL UAVs

[/img]http://tinypic.com/k2berq.jpg[/img]
The idea died because of forward flight speed limitations –but we could certainly look at doing it with a jet.



posted on Jan, 19 2006 @ 06:23 PM
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My appetite was sufficiently whetted by this thread that I got the urge to turn the X-29 into a fighter (in plastic of course) you may remember I mentioned it on here.

Well, I thought you might like to see a shot of how the 'F-29A Tigerbat' turned out






[edit on 19-1-2006 by waynos]



posted on Jan, 23 2006 @ 07:02 AM
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Nice modeling mate. Maybe one day you’ll have a model of the S-STOL concept on your desk, lol.

Further research
Looks like the only equivalent UAV program that would (if our project was for real, it isn’t) compete for deckspace with our S-STOL concept design is Aurora’s Excalibur:


The Excalibur weaponized UAV is expected to fly in 2007 (in demonstrator form). Although it is seen more as a replacement for the weaponized Predators, and I’ve not seen any mention of naval interest, the design is all the same inherently relevant to shipboard operations. Unlike our concepts, it is capable of vertical take-off and recovery, but it is comparatively slow (460kts) and with a very light weapons load (600lb – enough for Hellfire etc). To put that into context, we are aiming at a weapons load of 10,000lb. Clearly Excalibur will never be able to encroach on the anti-ship strike or cruise missile launch platform roles we envisage within the S-STOL concept.
www.aurora.aero...
www.aurora.aero...

The Excalibur would clearly offer advantages over our concept designs: stealth and vertical take-off/landing allowing operations from destroyers etc.

I am not sure exactly how it is VTOL capable.

I’ve commissioned a draft illustration of a low-observable version of our designs (sticking to the currently favored forward swept wing):

The need for shallow slopes on the flanks has prevented a lift jet being fitted (unless it was far smaller and/or more of them) so a lift fan is incorporated in its place. The air intake would be in the chin under the radome. As previously discussed, the size constraints do not allow for a meaningful internal weapons load. I am lukewarm towards the idea of attempting to incorporate stealth into our concept.



posted on Jan, 23 2006 @ 09:23 AM
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Wild throw into the air...
Could you use singleshot discardable booster jump rockets instead of the lift fan...
It would probably suck....



posted on Jan, 23 2006 @ 09:31 AM
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Northwolf, I like the phraseology, "a wild throw into the air" on both counts there



posted on Jan, 23 2006 @ 07:57 PM
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northwolf
Rocket assisted takeoff is certainly a good suggestion. One we should explore further. The landing distance is more of a problem though without the reverse thrust of the lift jet.

Possibly we could use some sort of arrestor rocket –not unlike the Russians used instead of parachutes for airdropping vehicles, which were successful and reliable. The rocket could be far smaller than the lift jet –and not use the already limited aviation fuel.

First thoughts are to use two solid fuel rockets which retract into the underbelly, firing at about 10 degrees off the centerline (so as not to fry the front landing gear, and to reduce the risk of burnt air ingestion). The removal of the lift jet would also allow more air intake positioning options, such as belly or chin.
Initial sketch:



posted on Jan, 24 2006 @ 10:46 AM
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Here’s a provisional configuration drawing for the D-0019 (rocket arrested landing S-STOL) design.


I’ve had the intake split into two so as top allow an uninterrupted centerline area for forward landing gear and targeting sensors.

The arrestor rocket could be far smaller than the lift jet and laid horizontally for minimum fuselage complications. The obvious choice would be a solid fuel short burn rocket motor. A single rocket mounted centrally with split exhaust has some complications (the exhaust) BUT, two separate rockets would have the far worse problem that if one misfired, the aircraft would veer violently to one side –almost certainly disastrous on an aircraft carrier landing.

As I see it, rockets have the advantages of being relatively reliable, low maintenance (simply replace motor every launch) and very compact. But they are also harder to control thrust levels (?) and impossible to stop once started. You wouldn’t get a second pass unless you had a spare rocket (?).



posted on Jan, 24 2006 @ 11:06 AM
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Waynos,

I'm still ogling your models.

Anyway, what do you think of the rocket arrestor idea? Seems so obvious I’m surprised it hasn’t been done before (if it has, you’d be the man who knows).

If we think it’s a runner, we could modify the bi-diamond configuration to incorporate it before modeling gets underway.

As long as the design can launch with a ski jump or catapult (customer specific variations envisaged for ‘small’ carrier, ‘medium’ carrier and land based operations), the landing becomes the only issue.


Also, re the bi-diamond wing. I propose to get the 3d bods to model a simplified bi-diamond design purely for (virtual) wind tunnel experimentation before undertaking the more complex task of modeling the full bi-diamond S-STOL design. This would allow us to try out minor variations like dihedral/anhedral, separation, over-lapping etc as well as get a general feel for how bi-diamond wings interact and perform at high angles of attack etc.

A good idea?



[edit on 24-1-2006 by planeman]



posted on Jan, 24 2006 @ 02:33 PM
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Planeman, I am sure I have read of arrestor rockets being trialled before, back in the 1950's, but cannot for the life of me remeber anything about it. It seems to be a brilliantly simple and lightweight solution and well worth a go. I also seem to remember it was also something to do with bringing a plane to a halt on a carrier, but I keep thinking C-130! This may well be wrong.

I also think your pan for testing the bi-diamond wing is exactly whats needed. Although I think the drawing you put up has too much span and not enough sweep but even so this too would be a good area to expriment with as poor results at one angle might not necessarily carry over to a longer/shorter wing.



posted on Jan, 24 2006 @ 05:49 PM
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As you say, brilliantly simple –why hadn’t we thought of that before. This is why I have so much interest in the A.TT ethos –unlocking innovation amongst non-industry people.

How about this? –the wings are shown straight but we can experiment with different dihedral/separation etc.


If this is OK, I can get an annotated diagram for the 3d modelers and we can put it through the Gerris flow analysis software.



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