Just read something in another thread that might be of interest to you guys.

Canards are now being considered for Tejas as additional control surfaces.
Even though this in not finalized, it does point to the fact that this is something they have identified as an area of improvement.

Kaduna2003, as per the articles posted earlier, canards were tested on scale-models of naval variant of Tejas. ADA rejected them and will install LEVCONs instead, as experiments showed that they did not result in increase of lift, stability or manoueverability.

As per the article quoted by you, there is no unanimity over the addition of an auxillary control wing which may not necessarily be canards, but similar to the small and immobile canards of Su-30 MKI.

Man you are dreaming and without even any aerodynamic real proof.

The reality is compounded wings are called double delta, the Draken and Concord have compounded double delta wings, the same we can say about the F-16XL and Su-27 see the geometry, however these last two aircraft can be considered a different type by some basic technical reasons

I disagree that no “aerodynamic proof” was provided by me. As per similar “aerodynamic proof” with supporting photos that was furnished repeatedly earlier, the Tejas has compounded AND a cranked wing structure, whereas Draken, Gripen are ONLY compounded and NOT cranked.

As demonstrated by photographs and technical papers from NASA, the cranked-arrow F-16XL has a different definition of ‘crank’, which seen from the top-view is the “abrupt” change of the wing’s angle of sweep. But as per the diagram of another research paper posted earlier, the crank is defined as the dihedra of the wing seen from front-view. The Tejas’ crank component of the wing, corresponds to the latter definition and not the definition of F-16XL.

This crank is formed by the slope over the Tejas’ lower-swept wing part (as demonstrated in a labeled photo posted earlier). It assists in vortex generation over the wing to achieve lift effectively performing the action of a canard to quite an extent.

The following photo demarcates the point location of the crank of Tejas’ wing, as seen from front-view.

This point is the confluence of the lower and higher swept leading edges. As noted earlier (again with supporting photos), as Tejas wing base is plain, this crank is apparently visible due to the combined effect of the compound and the slope over the lower-swept part.

See that in this article they say fluid mechanics of interaction between the strake and wing vortices of a generic 76°/40° double-delta wing leading to vortex breakdown, check the angles 76 deg is a high swept and 40 deg is low swept like the wing of a MiG-29 or an F-16XL not an AJ-37 or LCA

I disagree with the above. The abstract of the research paper has only taken 76/40 combination as a subject of the test, and neither does it conclude nor aims to conclude that this particular combination of sweep is superior to a wing of lesser sweep. It only tries to study the effects of vortex breakdown on an example 76/40 wing.

Here, I may personally advise you to comprehend the abstract and conclusions of formal research papers.

The LCA and Viggen have delta wings with a notch, some people might call them conpound since the leading edge has two sweep angles but by definition the real conpounded wing is the one seen on the Concord or Drakken

The above is inaccurate. The Tejas’ wing is outward compounded also. The Draken’s wing is inward compounded, whereas the Concorde does not have a “sharp” compound, but a smooth curve known as ‘ogee’.

Now all this talk by yours that the elevons are smaller in a delta canard configuration has no aerodynamic real base and the reason is in an aircraft like the J-10 it has number one two centers of lift since it has two wings and both have positive lift, flap deployment is less restrited but also the need for triming is reduced.

I disagree with the above. As per the detailed labeled diagrams of the Gripen’s cutout schematic and schematic of Rafale posted earlier, it can be observed that the actuator assemblies of these 2 planes are much smaller in comparison to Tejas’ elevon actuators. Thus, the elevons of these planes are expected to trim lesser than Tejas’ elevons in part because the canard is the primary pitch authority, and also in part because being subjected to ‘wash’, they anyway cannot “harness” their complete trim potential.

In contrast, the Tejas compensates for the lack of canards by elevons that deflect far much more than elevons of Rafale or Gripen.

Trimming will be relatd to stability, the tailess delta wing usually is neutrally stable to reduce the amount of pitching moment

The above is inaccurate. As per the official website of ADA, Tejas is highly unstable in the pitch axis, wherein it’s CG shifts in the sub-sonic and transonic regimes. It’s flight control is configured to bring back the Tejas to stable configuration every 12 milliseconds.

The value of the static margin, sm, should be large enough to provide acceptable handling qualities at the most aft center of gravity position. This may require an analysis of the aircraft dynamics at various flight conditions. Since the destabilizing effect of the fuselage is not included explicitly here the value of sm used in the above expressions should be increased appropriately

With this i am sure you will adduce the canard disadvantages but in reality you disregard the stability problems a tailess delta wing will have.

Note that Tejas’ handling during numerous flight-conditions has been tested in I disagree with the above. The Tejas has negative static stability, which is handled adequately by the flight-control computers that bring it’s frame back to stability every 12 milliseconds.

Though there is no auxilary wing to provide a moment to the most aft center of the CG, how the Tejas overcomes this disadvantage is enunciated below, using your own research paper.

Read this article about how the tailess delta wing has all the properties i have said before such as low drag but lack the trimming capacity of the tailed configuration
http://www.aiaa.org/content.cfm?pageid=406&gTable=mtgpaper&gID=45836
http://pdf.aiaa.org/preview/1986/PV1986_1838.pdf

and how it limits flap and leading edge deflection and if the LCA has larger flaps and elevons is simply to reduce the deflection of these devices, the J-10 or Gripen have relatively smaller elevons because trimming is also done by the canards

The above is inaccurate. The above papers mention how the tailless delta has low pitch-down authority when the CG is shifted aft at supersonic regimes. This results in instability.

Hence the paper suggests the addition of ‘fences’ on the leading edge of the wing that can trim to provide a counter-moment to the aft shifted CG. This is exactly the approach used by Tejas, in which 6 slats (3 on each leading-edge) are placed that trim to provide moment from the front, besides vortex generation.

Once again, I may kindly advise you to properly ascertain and comprehend abstracts like the above, for I think the above contradicts your core point of view that Tejas’ delta is disadvantage, whereas the paper details an approach that Tejas has in fact embodied itself. Another interesting point to note is that the paper is from an Indian research institute of the based in the US, and one author is Indian.

[B]Abstract : … The analysis is based on four canard geometries varying in planform from a 60-degree delta to a 25-degree swept wing, high aspect ratio canard. The canards were tested at several positions and deflected from -10 to +10 degrees. In addition, configurations consisting of a horizontal tail and a canard with horizontal tails are analyzed. [color=”blue”]Results of the analysis indicate that the canard is effective in increasing lift and decreasing drag at Mach numbers from subsonic to high transonic speeds by delaying wing separation. The effectiveness of the canard is, however, decreased with increasing Mach number. At supersonic speeds the canard has little or no favorable effects on lift or drag. It is further shown that the horizontal tail is a superior trimming device than the close- coupled canard at low-to-moderate angles of attack and that a configuration consisting of canard, wing, and horizontal tail is superior in performance, to either canard or horizontal tail at high angles of attack.[/blue]

The above abstract only summarizes that canards are ineffective at supersonic speeds, maybe even detrimental. The horizontal tail is shown to be superior to the canard design at low to moderate AoA. The paper neither mentions tailless delta devices, nor compares them with Su-35.

And at least i post articles published by NASA no speculation, you are posting your opinions without any base upon NASA or reknown french institutes, but you only post your opinions without any real aerodynamic base.

I disagree with the above. 2 NASA papers from 1959 and 1996 have been posted and analysed earlier, as per whom the wing cranks are shown to be effective for stability and lift. A research paper that diagramatically shows the wing crank of an experiment, also arrived at a similar conclusion. Supporting photos of Tejas’ slope above the lower-swept part have been posted a few times earlier.

Detailed comparisons with detailed labeled schematics of Rafale and Gripen have also been done.

But nonetheless, the Europeans did and the Israelis also went with it. The Japanese also had canard-delta concepts of their own. As for the Russians, MIG did seriously propose its MiG 1.44 and Sukhoi did implement canards on its Flankers. The US also implemented canards on its B-1B. Are you familiar with the X-31 super maneuverability study?

crobato, please note that that current US and Russian planes have not implemented either the canard or pure delta designs. As mentioned earlier, atleast delta planes were brought into service by US and France, however none of the canard-delta planes have ever been introduced into service by US and Russia.

I stand corrected that the US and Russia have indeed experimented at least on the canard-delta designs. I was aware of X-31, however while typing the post it escaped my recall.

Nonetheless it showed DRDO pretty much alone in this one, against an opinion that is made up of Dassault, SAAB, IAE, Eurofighter consortium (BAE, Messerschmitt, etc,.) and MiG.

I disagree with the above. Note that up to only 8 months earlier, the Mirage-2000 also had active production; however it’s production was halted after the “wake” of Rafale. As late as 2006, France offered this plane to the IAF, and before the MRCA proposal was mooted, the Mirage-2000 was the IAF’s main choice for 126 planes.

Besides, it may also be noted as per the research paper posted by MiG-23 MLD (and various others available) that the experimental delta F-16 XL was concluded to be superior to the F-15 that was in service; however, the “momentum” with the F-15 was begun and so commitment towards it was not changed.

An elevon part times as an aileron and as an elevator. But unlike canard-deltas and tailed planes, an elevon cannot function in one moment of a time, as both aileron and elevator, because aileron and elevator is functionally an “or” proposition.

As discussed earlier, the Tejas’ elevons are independent of each other. A simultaneous pitch in the process of executing one roll can be performed by deflecting one elevon more than the other, in the same direction. A “pure” roll is performed by elevons equally opposing each other, while a “pure” pitch is performed by elevons equally assisting each other.

A delta plane can thus perform ALL the manouevers performable by a conventional tailed plane, as well as canard-delta plane.

That does not constitute a droop. No plane can change any wing position from anhedral to dihedral or vice versa, unless you can flap wings like a bird. Note the elevons are down while the canards are pointed up just as I described.

I disagree with the above. In the frontal photo of J-10 while taxiing, the canards only appear “upturned” as their aft portion is hinged upwards (note that the aft is wider). However, as in the photo posted by me earlier in this photo, they are clearly oriented down at the wing, and in this photo they are clearly flat.

Actually presently canards in all planes are hinged (unlike Viggen’s canards, which were fixed and that had “elevon” like structures at aft). As I am unable to view the photo from CDF, you may please post it on this thread.

Wrong. Canards don’t need to because they have a fresh air stream in front of them, unlike control surfaces tied to the main wing that have to deal with the wake from the wings’ front edge as well as the boundary layer that forms around the wing. You simply cannot ignore even the late fifties studies about why all moving control surfaces are better. In fact one of the reasons why canards are generally smaller than tail planes is that they can generate the same amount of control authority for less size and deflection.

I disagree because as seen in this photo of Tejas ( photo courtesy : Colonel Ajai Shukla), it may be subjectively observed that the elevons are “huge” in size and so command a significant leeway over the incoming airflow. So they may not always be at “mercy” of wing wake, turbulence etc. Tejas’ elevons may also be seen in this photo also (magnifiable).

However, during flight, they are not seen trimming as much as shown in the photos because small trims suffice to achieve the manouevers. In contrast, smaller control surfaces have to trim more to achieve the same effect if they are the primary pitch authority; if assisted by elevons even if ‘washed’, the trim may not be as much.
To illustrate the importance of sheer size as a counter example, one may ‘imagine’ had the elevons on Tejas been 50% of their area (same as a canard’s size on the J-10). By this basic flight manouevers may have been impossible.

And even if they are turned to pitch, canards generate lift even for the drag they produce. Control surfaces on the trailing edge of the wings however, have to push the aircraft down on its tail to move the nose up, and hence they create negative lift while exerting drag at the same time.

The above may be possible, however the rate of pitch will be the same regardless of positive or negative lift. Again the loss (or gain) of lift may be negligible of the order of not more than few feet. Also, the gain by canards will be negated by the elevons at opposite end, that will effort to lose lift.

I think the debate may not be continued further, as it is increasingly descriptive and speculative now. In my view, the J-10 and Tejas are likely to have equal agility.