Haavarla, here it is @ 14:00:

https://youtu.be/rwf98F_VvkQ

Incidentally, here from 10s to 20s we see the T-50’s post stall flat spin. Firstly controlled by differential LEVCON deflection (port) and then corrected by differential LEVCON deflection (starboard):

https://youtu.be/i2VvxUy2-Xg

If those aren’t yawing moments, then I don’t know what are.

…I doubt they are used for that, but don`t want to comment on that because I don`t know. In any case they managed to do more with less. Much smaller vertical tails reduce RCS, drag and weight and are fully movable which has many other advantages.

Specifically for supersonic speeds, I would speculate that differential LEVCON deflection, where one is loaded and the other unloaded (with only a minor drag penalty), would create the required pressure differentials for directional stability/yaw control – but the deflection angles would be marginal compared to the acute angles seen in the subsonic regime.

Remember, the T-50 avoids both the F-22’s humongous vertical stabilisers and the J-20’s ventral fins for good reason.

I know it has all to do with subsonic AoA, in terms of placement, size and angle. Incase you didn’t read earlier – I got this direct from the horses mouth.

Do you realise that levcons operate in the vertical plane, whereas vertical fins and stablisers are mainly horizontal (lateral?) OK, you could argue roll control in differential movement, but that is not lateral stability.

Furthermore, do you not realise Levcons are there to (1)reduce drag in level flight and (2)act as a more optimised alternative to fixed LERX at high AoA? In supersonic flight, you don’t do high AoA.

You can quote that little power point all you want, but tell me this, do aircraft still feature auxiliary wing flaps to deal with compressibility over aerofoils? Of course not – design has moved on.

:rolleyes: The difference between being able to read and being able to comprehend I guess.

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

Meantime, let me enlighten you on a principle function of the LEVCON:

Wind-tunnel testing also showed that differential canard deflection was capable of generating yawing moments of roughly the same magnitude as the thrust vectoring vanes currently in place on the X-31 in the post-stall regime…

http://ntrs.nasa.gov/search.jsp?R=19960012279

Me thinks you might need to add a Point (3) to your paragraph above.

By M you mean? Mach?

M = Mach?

No, I meant Mangoes.

Cop-out.

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

Wind tunnel results showed an ultra-sensitive relationship between the placement of the vertical tails and the design of the forward fuselage. The interactions could not be predicted accurately by analysis or by computational fluid dynamics*. The airflow over the forebody at certain angles of attack affects the control power exerted by the twin rudders on the vertical tails.

http://www.codeonemagazine.com/article.html?item_id=180

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

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

If so, who told you increasing Mach = reduced lateral stability? [for a fixed vertical fin size]

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.

…then again the big vertical tails of the F-22 are large for a reason.

I would guess it’s the inverse relationship between directional/lateral stability and increased M, anyways thanks for finding the links.

Actually, there may be an additional reason why the T-50 has dinky tail fins- I just remembered it has another tool at its disposal as regards directional stability. Below, it corrects an anti-clockwise flat spin whilst free falling (you can see a near vertical vortex stream off the tip of its nose).

The fully deflected starboard LEVCON induces a pressure differential which counteracts the spin on its yaw axis (also the Cg) and in conjunction with TVC, drags the nose to starboard.

Though TVC greatly assists, this is testament to the power of the LEVCON as a lateral control surface (aside from high AoA), still operating in attached flow when wing and elevator are already fully stalled.

Because the T-50 and F-22 are dimensionally similar. I’ve provided frontal views of both the F-22 and T-50 side by side, both are from official sources (from USAF, and from Sukhoi patent, respectively), and their frontal areas are almost the same…

You’re doing it again! When accurate dimensions of the T-50 are not known simply scaling up or down a frontal view simply won’t cut it. You know full well it is the smallest increments that can make all the difference (e.g. Eurofighter AMK).

Objectively, you will have to acknowledge that the F-22’s forebody does indeed look a lot fatter (specifically the cross-sectional area) than the T-50’s – this is primarily due to intake/S-duct and w/bay arrangement.

The dearth of accurate/credible details means this ‘eyeball’ analysis is perfectly valid- much the same as visually comparing a 757 with a 767.

Nothing to do with ac, they’re talking about hardware architecture and their version of this:

https://news.samsung.com/global/samsung-begins-mass-producing-worlds-fastest-dram-based-on-newest-high-bandwidth-memory-hbm-interface