Canard vs conventional wing set up

AFAIK Close coupled canard can generate vortex which will increase lift coefficients, in a simlar fashion as LERX. Admittedly with slightly different vortex routes






an aircraft can have both LERX and canard at the same time.

Canard can also be made with smaller size than the horizontal stabilator of conventional wing set up => help with both weight and drag reduction.

Would it be a correct statement to say if radar cross section isn't a concern, canard set up is better than conventional set up
as it allows better kinematics performance? ( better CL, lower weight and drag)
Iam wondering this since many new aircraft seem to be more interested in canard configuration



canard was the choice for the HiMat also

A canarded delta planform will not have as steep of a lift curve slope due to the nature of the delta wing. This layout will also have a low max AoA. If you recall, the Tiffy is getting an agility enhancement that includes small LERXs that increases the max AOA to around 35. Compare this to unstable conventional tailed planes such as the Super Hornet, Raptor, and Lightning which are all 50+ AoA fighters. If you look at the Rafale planform you see that it has a small LERX on the wing and another on the canard (this one is really thick and rounded, but it will still have similar function aerodynamically). In your vortex picture for the Rafale you even see vortexes forming inboard and ahead of the canard. As such, the Rafale is the layout you describe wanting to see. In terms of being "better" a canard setup and an unstable tailed design both offer increased CL, lower weight (due to structural loads), and reduced (trim) drag.

sprstdlyscottsmn wrote:A canarded delta planform will not have as steep of a lift curve slope due to the nature of the delta wing

How about if they used conventional wing instead of delta for canard set up? such as the one on Su-30MKI. Is there a particular reason for delta wing in canard set up?

AFAIK, even though canard - delta have less steep lift curve, they are can still have better ITR due to higher wing area compared to conventional set up ( case in point Mirage vs F-16). The less steep curve seem to harm its STR though.

sprstdlyscottsmn wrote:This layout will also have a low max AoA. If you recall, the Tiffy is getting an agility enhancement that includes small LERXs that increases the max AOA to around 35. Compare this to unstable conventional tailed planes such as the Super Hornet, Raptor, and Lightning which are all 50+ AoA fighters

I know the Typhoon has low AoA limit but i always thought it is due to long arm canard vs close coupled canard on Rafale and Gripen.
Didn't the Rafale reach AoA of 100° and Gripen reached AoA of 80° in test? i know their FBW limits their AoA down to much lower value of around 20-30° in operational but regardless.


http://forum.keypublishing.com/showthre ... d-4/page48

Another possibility for low AoA limit of those Eurocanards that i could think of is the fact that they only have single vertical tail, so may be that limit their control authority at high AoA, which mean they can reach high AoA but not really swinging their nose around like aircraft with twins tail such as F-35 or F-18. However that seem to be the disadvantage of single vertical vs twins vertical tail rather than of canard-delta vs conventional set up. (for example: F-16 has very low AoA limit despite not having canard delta set up)
http://forum.keypublishing.com/showthre ... ost2381116

sprstdlyscottsmn wrote:In terms of being "better" a canard setup and an unstable tailed design both offer increased CL, lower weight (due to structural loads), and reduced (trim) drag.

i see. But would you say canard is better at the job? since evolution from F-16 such as J-10, Lavi and Himat all use canard set up, pretty much all fighters that doesn't have RCS as priority use canard by now

Often the lower AoA limit is due to the single tail because directional stability is reduced as airflow over the vertical tail is lost - e.g MiG-23MS was prone to depart and flat spin over 24 degrees.

Two advantages of twin vertical tails are better high AoA capability and better supersonic yaw control. Single tails are shielded from some airflow at high AoA by the fuselage, thus less effective. Some of that effectiveness can be regained by making the tail taller to get into stronger flow. But tall vertical tails are more flexible, especially in twist. At supersonic conditions, that twist flexibility results in loss of rudder effectiveness or in extreme cases, rudder reversal. So twin tails, being shorter, are stiffer and maintain rudder effectiveness better. The interaction between tail and LERX vortex flow has its negative side, due to the severe buffeting on the tail structure. Early Hornets suffered from unexpected cracking in the tail structure.

More ancient history. During YF-16 configuration development, a twin VT version was tried, but for the versions tried, showed no improvement over a single tail.

viewtopic.php?f=60&t=27592&p=296410#p296410

The single tail of course has less weight/drag and had better directional stability under 25 degrees it seems.

Seem to remember reading one reason the YF-17 had two tails was specifically to get high Alpha handling - on the other hand the F-14 had 2 tails and could go to 50 degrees but it didn't have the control power to make much use of it - and the pilot basically was departing it (US Navy).

The Cranked Delta on the F-16XL somehow provided better directional stability and was extended to 29 degrees.

Not much on it but Canard Delta was evaluated for the F-16 but seems to have been judged too heavy and complex - but that was back then.

Canards V Tails has been discussed a few times viewtopic.php?t=9780 - think it is more donw to specific implementation and technology available instead of just one is better than the other.

It seems to me that you can get most of the benefit of a canard arrangement by properly designing the forward fuselage of a tailed aircraft. I think you could even make a stable tailed design with no trim drag by adding chines or leading edge extensions that angle downward from the nose to the wing root (the F-35's angle upward).
Now, the interesting part is that adding canards to a stable design can make it unstable, giving you the benefit of instability in maneuvering while making the plane still controllable if the control software fails (by letting the canards free-stream). Not really an issue for modern jets, but might have been exploitable too give more agility early in the jet age.

count_to_10 wrote:It seems to me that you can get most of the benefit of a canard arrangement by properly designing the forward fuselage of a tailed aircraft

From what i understand canard improve CL by vortex while unstable wing tail design improves CL by negative stability. Canard + LERX seem to improves CL by bigger margin than LERX alone, but that is offset by the delta wing. What if canard is used with trapezoid wing? why isn't that more popular?
and if canard have the same efficiency as tail configuration then how come so many new fighter uses canard.

basher54321 wrote:Often the lower AoA limit is due to the single tail because directional stability is reduced as airflow over the vertical tail is lost

Actually now that i think about it, may be the delta wing block even more airflow to vertical tail at high AoA
The question is: why isn't trapezoid canard more popular?

The optimum location for a canard is on somebody else's aircraft...

garrya wrote:
Would it be a correct statement to say if radar cross section isn't a concern, canard set up is better than conventional set up
as it allows better kinematics performance? ( better CL, lower weight and drag)
Iam wondering this since many new aircraft seem to be more interested in canard configuration

IMHO
a/
RCS is not a factor for choosing tail or canard
b/
If one is better of the other depends on your mission
c/
kinematic performance is more about nitty gnitty desing in the end (or the right Engine)

If you have the energy, read trough this:
http://raf-fly.blogspot.se/p/aerodynami ... ourth.html

Its a summary of the Gripen design choices from one of the aero guys where he talka about the benefits of tail and canard.

The internet article is quite old, and the images seems to be gone for me, If you don't find them and if someone is interested I'll see if I can dig them up.

regards

linkomart wrote:IMHO a/RCS is not a factor for choosing tail or canard

AFAIK, canard are often not on the same plane as the main wing so it will increase RCS somewhat from frontal aspect. Moreover the gap between the moving canard and surface will cause scattering but without the main wing to block it

linkomart wrote:b/If one is better of the other depends on your mission

So in your opinion in what case canard is better and vice versa?

linkomart wrote:c/ kinematic performance is more about nitty gnitty desing in the end (or the right Engine)

I understand that engine is important but surely wing design matter alot for CL and Cd

linkomart wrote:If you have the energy, read trough this:
http://raf-fly.blogspot.se/p/aerodynami ... ourth.html

The link doesn't work somehow

garrya wrote:AFAIK, canard are often not on the same plane as the main wing so it will increase RCS somewhat from frontal aspect. Moreover the gap between the moving canard and surface will cause scattering but without the main wing to block it

tailed non stealth aircraft often don't have the wing and the tail in the same plane. There are often good reasons to separate them vertically. Yoy can not (easilly) do that on a stealth Aircraft, tail or canard. To put the wing and tha canard in the same plane will give drawbacks for both configurationa, MAYBE a Little mor for a canard, byt I'll not bet a lot on it.
J-20 has the canard and the main wing in the same plane and it works in the wind tunnel and in the air.

linkomart wrote:b/If one is better of the other depends on your mission

garrya wrote:So in your opinion in what case canard is better and vice versa?

Maybe but not definately if range is the key performance driver the tail is better, othervise canard, but no, I can not say for sure wich one is better. I have made some studies at work and the ratio is about 50-50 for tail vs canard... stealth or not. It is trickier to design a canard, so if you don't have the data, don'tdo it is perhaps the best I can say.

linkomart wrote:c/ kinematic performance is more about nitty gnitty desing in the end (or the right Engine)

garrya wrote:I understand that engine is important but surely wing design matter alot for CL and Cd

hmm, yes. Sweep and flaps are also important, more than canard or tail configuration I would say. OTOH the configuration often sets the max avaliable flaps and sweeps so...(edit clarification)

linkomart wrote:If you have the energy, read trough this:
http://raf-fly.blogspot.se/p/aerodynami ... ourth.html

garrya wrote:The link doesn't work somehow

Hmm, it works for me. PM me and I'll send you a Word copy.

regards

When links don't work for whatever reason you can try copy-pasting their urls into Google, search, find the green url under the top result, click on the arrow at the end of that green url and then click on 'Cached' to get a Google-stored copy of the site:

http://webcache.googleusercontent.com/s ... clnk&gl=au

Dragon029 wrote:When links don't work for whatever reason you can try copy-pasting their urls into Google, search, find the green url under the top result, click on the arrow at the end of that green url and then click on 'Cached' to get a Google-stored copy of the site:

http://webcache.googleusercontent.com/s ... clnk&gl=au

Did you get it with images or is it just my computer?

linkomart wrote:Maybe but not definately if range is the key performance driver the tail is better, othervise canard

So that mean tail configuration has lesser drag?

Dragon029 wrote:When links don't work for whatever reason you can try copy-pasting their urls into Google, search, find the green url under the top result, click on the arrow at the end of that green url and then click on 'Cached' to get a Google-stored copy of the site:

http://webcache.googleusercontent.com/s ... clnk&gl=au

For some weird reason, even the cache link doesn't work for me