Am i the only one who finds discussions in last few pages mind numbingly boring…?

Of course its boring (even for me).

But at least half of it is based in reality rather than speculation based on nothing! 🙂

There are some major differences between LEVCON and canard.
Canard produces downwash effect that has impact on the main wing.

When at high AoA, the downwash component is not a factor. It is in this flight regime that the canard starts to function as a LEVCON.

i.e.

Note also the angle of incidence, which:

LEVCON also delays stall in the way it feeds the LERX with airflow because it can position itself at lower AoA in relation to LERX.

As for whether LEVCON can be fixed or moveable. There are (peer reviewed) papers that call a fixed feature a Leading Edge Vortex Controller, but they are non-public. i.e.

http://arc.aiaa.org/doi/abs/10.2514/6.2008-336

A more public hand waving description:
https://www.flightglobal.com/news/articles/flight-test-alenia-aermacchi-m-346-one-stop-warri-207881/

The wing was moved up the fuselage, having been too low on the Yak-130 and causing horizontal stabiliser blanking at mid to high angle of attack (AoA). The leading-edge extensions (LEX) were reduced and redesigned to give controllable vortex lift. Two small vertical fins were added at the wing roots to “trap” and control the LEX vortices at AoAs from 25-30° upwards. These LEX vortex controllers ensure the “vortex burst” over the wing at high AoA is symmetrical and controllable.

It doesn’t have to be moveable to control the vortices, and do so with different responses over a range of speeds and AoA.

I don’t have time to hunt out better references right now…

It seems Russia has gone from having point defense fighters in previous decades, to long range, multi-purpose fighters (which makes sense given their territory and requirments). So perhaps Russia does not have a true aversion to single engine fighters, but the performance requirements of a big, capable, long range fighter almost always drives the design to twin engines. Happy to be corrected.

But Russia is probably the most comparable country in the world to Canada… hence MSphere’s thought train.

MiG-31s for the Canucks! 😀

Well, why don’t you enlighten us with these new devices for supersonic yaw control?

You don’t need much in the way of fancy devices if you reshape the fuse to avoid it inducing the unstable yaw moment in the first place.

Meantime, let me enlighten you on a principle function of the LEVCON:
Me thinks you might need to add a Point (3) to your paragraph above.

I’m sure you’ll also enlighten me as to how the PAK-FA or F-22 does this.

Furthermore, while a canard is usually always a LEVCON, a LEVCON is not always a canard.

Your missing context, a lack of understanding and comprehension of what applies where and when.

Charging headlong off a cliff is becoming a habit of yours:

*Obviously CFD software used on the T-50 has come a long way since the late 1980s.

CFD is not a pancea – I doubt that Suhkoi are satisfied with their DES and LES fidelity for PAK-FA.

The F-22 evolved from the YF-22 in the 90s – a test campaign which will always provide better results than CFD. The details of the aerodynamic platform changed substantially.

I already told you the forward fuse (the chines) was a big influence on the vertical fins, why are you repeating it back to me and acting as if you are providing insight?

Page 11 or 6/21:

https://www.google.co.jp/url?sa=t&source=web&rct=j&url=http://www.princeton.edu/~stengel/MAE331Lecture22.pdf&ved=0ahUKEwjUhZHC_bDLAhXFbxQKHfrKD-oQFgggMAM&usg=AFQjCNFdzYpQvfIuZ9IprA2zoBjKDCZ-zA&sig2=JeVu2P7I_YVb_E5ZF0Dang

Note what the F-100 solution was.

Note those are 1st generation supersonic designs.

The exception being the XB-70, which used the folding tips for multiple reasons, admittedly relaxing design rules due to stability considerations was one – but they would have redesigned the fuse if they weren’t getting lift benefits from the tips.

Aerofoil design and fuselage design has evolved much since, with consideration for effects of supersonics in yaw.

Take your pick.

There will probably be more than one or two corners of the envelope where F-22 is better than PAK-FA. The wings do all sorts of torsioning under load to adjust aerofoil profile. Its just not possible to have that ideal over all flight conditions. There will be differences between the philosophies of the design groups which will lead to differences in performance in different parts of the flight envelope.

Never said they could.

Then why bother stating them?

Does vertical stabiliser effectiveness (directional stability) increase or decrease with increasing M?

By M you mean? Mach?

Utterly irrelevant. At supersonic speeds you’ve too much vertical tail area (and that applies to PAK-FA too).

You’ll find the answer in US DoD GAO reports from a decade ago.

It wasn’t a question. I know from the horses mouth what the story was.

I implied fin sizing was indicative, not a reason.

Cop-out.

In which case, out of the T-50 and F-22, which adheres more faithfully to the ‘Area Rule’?

Have you mapped them through the longitudinal axis?

Which is likely to have the superior aerodynamic lift-to-drag ratio?

In what flight condition?

This is before we even get into elements like airfoil-BL seperation, chord, supersonic wave and trim drag etc.etc.

Which are things one cannot discern from photos.

For example, the F-22 has humongous vertically stabilisers. Why? Probably because the non-linear airflow patterns emanating from the engine inlets, chines and wing root are particularly acute and therefore require huge vertical fins with a large surface area to provide directional stability during supersonic flight conditions.

W.T.F?

The large vertical fins are there for high AoA subsonic flight, not supersonics.

To what extent the T-50 utilises TVC for yaw control at supersonic speeds is open to debate, but I would suggest that it’s dinky-all moving tail fins are testament to its superb (particularly trans & supersonic) aerodynamic design.

You don’t need much in the way of yaw authority at supersonic speeds.

Obviously, for the F-22 this means an increase in weight of the vertical stabs (and, consequently, the aircraft as a whole) – as well as an increase in drag. The F-22’s vertical stabs also required structural strengthening and partial redesign as a direct consequence of unforeseen high buffet loads and vibration midway through its flight test programme. This would suggest the aerodynamic *problems* are particularly endemic.

Not really. It suggests the two vortices off the chines are loading/unloading the vertical fins at particular parts of the high AoA flight regime, but doesn’t say much beyond that. Its not ideal, but may still be optimal.

If you want an example of an aircraft with severe aerodynamic problems, look at any Hornet variant.

Yes the F-22 has an outstanding T/Wr, thanks to its F119s which it needs to put to good use – but which is the most aerodynamically efficient?

I believe it is the PAK-FA.

But not because of the vertical fin sizing.