Crobato

Please understand this fact
The high pressure air from the lower surface of the LEX rolls around the edge to the lower pressure region on the upper surface of the LEX

The LERXes create vortices due to the difference of preassure from higher pressure underneath the wing to lower pressure above. same canards

However LERXes have no trailing edge, Canards do and the canard trailing edge is ahead of the main delta wing leading edges, that is the reason canards create a wake

some more about canards vortex formation

The effect of a canard on delta wing vortices was investigated in the 2 x 3 ft water tunnel at Wichita State University. It is well known that the leading-edge vortices generated by a delta-shaped wing greatly enhance a vehicle’s performance at high angles of attack. In this experiment, different canards were placed in front of a 70-deg swept main delta wing. Dye flow visualization was used to observe the vortex breakdown location during dynamic pitch-up and pitch-down motion with varying pitch rates. Compared to the no-canard configuration, results showed that there was a delay in vortex breakdown because of the presence of the canard and the dynamic pitch motion. The most favorable delay was obtained when the canard was located closest to the main delta wing and the model was pitched up at a fast rate or pitched down at a slow rate. Complete vortex breakdown on the main delta wing (i.e., full stall) occurred at 53 deg for the static case without canard. In comparison, complete vortex breakdown occurred past 90 deg when a canard configured delta wing was pitched up at the fastest rate tested (i.e., k = 0.2).

source]

If you see the Rafale closely coupled Canards are better They are the most favorable configuration for vortex breakdown delay because the Rafale`s canards were located closest to the main delta wing

This experiment studies the interaction of vortices shed by the canard and wing’s leading edges, and their effect on the aircraft aerodynamic characteristics. A close-coupled canard-wing configuration was selected and tested in different wind tunnels and at different conditions. Tunnel and model size effects, Mach number, angle of attack, and spanwise blowing effects on the vortex interaction were analyzed. Intrusive (hot wires) and non-intrusive (laser doppler velocimeters) data acquisition techniques were used and compared to enhance the reliability of the results. Flow visualization by tufts, oil, and laser light sheets were employed. Mean velocities, vortex turbulence intensities, and Reynolds stresses obtained for different conditions were compared and found to be generally consistent. Mach number, wind tunnel, and model size effects were in general small. Turbulence intensities and stresses increased with angles of attack. Spanwise blowing produced a small favorable effect. The use of a coplanar canard produced a small favorable interaction between the leading edge vortices, while the off-set canard produced a considerable increase in the lift/drag ratio. Keywords: Vortex flow; Subsonic flow; Close-coupled canards; Vortex shedding.

source

The use of a coplanar canard on the Su-33 produced a small favorable interaction between the leading edge vortices, while the off-set canard produced a considerable increase in the lift/drag ratio.

Maybe you should read english more closely. There is nothing there that says the canards produce leading edge wake at least short enough to affect the main wing. They produce leading edge vortices, and showed they will last longer at higher AoA before degenerating into wake, and all these articles point to the POSITIVE use of canards vs. LERX.

CTTE test pilot Li Zhong Hua seems to be getting celebrity status these days.

Crobato stop saying things are not true

The Su-27 and MiG-29 have highly swept LERXes of around 75 deg-85 deg ( i do not have the exact number)and less swept wings of 40 deg-65deg.

What? Have you seen the planform of the Su-33, Su-33UB, Su-30MKI etc,.? The wings appear even less swept than on the LERXd Flankers.

You are the one saying what is not true.

LERXes create vortices and this vortices burst near the fin creating fatigue it is true but they do not create a wake like a canard in front of the wing simply because they are not separate from the wing there is no gap between them and the wing and second they do not have trailing edges.

which is true. However, LERX vortice can also flow over the main wing and tail and this also creates buffeting effect.

Between LERX and canard, the vortices in the LERX is more likely to degenerate into turbulence at higher AoA because the LERX is a fixed device and cannot angle to suit the angle of attack. With a canard, the canard can adjust itself to the angle of attack, producing the righ angle or trim that stabilizes the airflow, preventing the vortices degenerating into turbulence.

Somehow you failed to get the picture that canards act as a variable LERX.

Because LERX is fixed, it will always generate drag and wake even in straight flight, but a canard can trim and even out so it presents a straight profile to the airstream, less drag and no wake.

Canards also have the same trouble they create vortices that burst near the fin too and their trailing edges are ahead of the main wing leading edge

And somehow you forget that airflow to the LERX also burst right at the root of the LERX to the fuselage, where the LERX bends and where the LERX meets the main wing. As a result LERX actually diverts part of the wake right under the wing whereas canards above the wing doesn’t.

LERXes are blended with the wing like the GOTHIC WING of the concord that changes its swept as the leading edges move toward the trailing edge.

And somehow you forgot that canards are blended on the Rafale to the body. J-10 uses body blending on its main wing, which also allows for considerable internal fuel capacity.

You can compare LERXed aircraft of roughly the same internal weight—JF-17 and Ching Kuo vs. Gripen. JF-17 internal fuel volume is roughly the same as Gripen while Ching Kuo is lower, though DSI version of JF-17 now has slightly more fuel because of the internal volume of the DSI bumb itself.

The is an article in “another” avaition mag this month about the US testing MiGs, Constant Peg, Red Hatters etc. Anyway, the article states that American pilots were incredbily impressed with the turning rate of the -17, and in particlaur were impressed with the design of the wing. One pilot/engineer (cant remember which) called it “a damn near perfect wing.” I’ll see if i can find out more when i go back to the bookstore tonite.

The wing is designed with its compound sweep, which pointed to the future direction of sweep wing designs, with different geometries in the inner and outer part of the wing.

Depends highly on the speed and altitude. If a MiG-17 meets a Phantom at M0.9 and 30000ft, the MiG-17 is pretty much on the edge of its envelope and will make curves like a supertanker, as while the Phantom is quite sporty. Different thing at M0.6 and 5000-10000ft (where Vietnam era dogfights often took place). Here the Phantom (and the MiG-21) is scratching heavily on its maximum lift limit, while the MiG-17 can fly quite unrestricted

The real failure of the MiG-17 design is the use of the T-tail. Maybe I should have mentioned it also in the Starfighter thread, but T tails generally don’t give good authority at high speed. I think that affects the Starfighter (never renowned for its maneuverbility) as much as the MiG-17 when the speed reaches to a certain point. If you look at the planform you will see the elevators are rather tiny compared to later MiGs for example.

So while the plane turns excellently at slow speeds, it becomes a slug at higher speeds, thanks to the tail plane. The fact that the long wingspan impedes on the rate of roll adds to the problem.

This leads to the introduction of all moving tailplanes in the next design, the MiG-19. The MiG-17 itself corrects on the MiG-15 by adding hydraulic controls, afterburner, and radar ranging gunsights.

Here is something some people wasn’t really aware of.

There is no “original” Russian made double seater MiG-17 at all. There was never a two seater MiG-17; the Soviet Union deemed the MiG-15UTI to be adequete.

All the two seater MiG-17s ever built, the so called “MiG-17UTI” were actually Chinese JJ-5s, presenting the first ever case of the Chinese seriously modifying a Russian design for their own purposes.

was produced by the thousands by the Chinese

True J-5s were never built in China by the thousands. More like hundreds. Ironically, more JJ-5s (at least over a thousand) were built than the single seater J-5s. Many of these were imported into the United States as warbird collectors and for evaluation testing.

Looking at recent pictures of PLAAF flight academies, it appears that the JJ-5s are still there in operational status and meticulously maintained.

Wow and it so happens the link happens to have a neat gif of plane planforms.

http://www.mach-flyg.com/utg80/bilder/fullsize/80jas1.gif

Here is a nice article that Proves you canards do affect the wing an generate drag even proportionally more than a tailplane and do affect the wing lift

You cannot take simulated data and think you can apply it with every specific plane design out there. Every plane design is unique. There is no “universal” rule as follows. You don’t even know the context of the model being used to generate those graphs. They would certainly not apply to the EF, Gripen, Rafale, J-10, Lavi, Valkryie, X-31, etc,. Every aircraft has their unique characteristics and graphs. Don’t attempt to misuse data, as you apparently don’t know what is behind it.

As I mentioned before, the one issue is the wake of the canards not against the wing but at the tail rudder. This can create buffeting or turbulence at higher AoA, but then that is also true of tailed LERXed aircraft , where vortex from the LERX might hit the tail rudder (one of the solutions maybe is to increase the size of lower ventral tail surfaces).

canards might be smaller but they produce more drag and they affect negatively the main wing lift, however they also have benefits.

How many times do I have to tell you again and again and again. Canards do not affect the main wing lift, not if the canards on a different plane than the main wing. Do you understand English?

Canards even if they are canted they still produce a trailing edge wake and vertical fin buffeting, if they cant the canards the wake is farther from the wing but still it creates a wake and affects the wing of course in a lesser way but still has a wake and the moveable canards still affects the wing when it operates as a control surface reducing lift to the main wing and inducing drag in fact canards are used as aerodynamic brakes .

Wrong again. The wake would fall behind the canard and OVER the main wing but would not for some reason, manage to miraculously sneak under the main wing.

You have no idea about putting pictures like the Gripen with the canard on the down position. Since the canards are down, the nose is headed down, and guess where the wake will go? UP. How does that affect the main wing eh?

Why don’t you take a good look at the aircraft once again?

The canards and the main wing of planes like the J-10, Lavi, Gripen and Rafale are **NOT** in the same plane like the Su-33/35. They are higher than the main wing. For turbulence to reduce lift, the turbulence must affect the airstream at the lower part of the wing, and that is simply not possible with biplane layout canards because the wake is well above the main wing. The fact that the canards are dihedral, while the main wing is anhedral, increases the seperation of the canard plane and the plane of the main wing.