Canted tails?

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I saw that the F-15 Silent Eagle has its vertical stabilizers canted at 15 degrees, like the F-18 but not as dramatic an angle as the F22. Is this the latest fad/discovery? What's the principal advantage?...besides looking sexier.
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Vertical tails form a radar reflector when viewed from above.

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How serious aerodynomic challenge does it present? Canted tails do generate some lift!? Why doesn't Su 35 have them?!
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???? Even canted tails form reflectors, only at different angles.

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True if that is the case, but then you would have two producing it vertically and only one at a time canted, so would in effect reduce the return by 1/2
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But that is exactly the idea of stealth and egde alignment, isn't it? To concentrate the carrier's RCS into several discrete peaks while maintaining very low RCS at all other angles. When viewed from above, an aircraft with canted tails has two angles with high RCS while one with straight fins only has one (even if teh absolute RCS value at that angle is higher)

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- A vertical tail is more likely to produce reflect returns to an opposing aircraft in steady level flight. - Outwardly canted tail is more likely to produce reflect returns to a ground radar (from the nearside tail). - Inwardly canted tails will direct the signal upward to space, with the fuselage partially blocking the far-side tail, thus attenuating the signal reflected toward ground/"useful" air. - If the vertical tail and elevator are at perfect right angles to each other, then reflected waves will do a "double bounce" through 180 and back to the emitting aircraft. - Outwardly canted tails offer significantly more lateral authority at high AoA. - A single tail will tend to be larger than the individual areas of 2 tails, thus two canted tails will generate less of a return at any given azimuthal angle. - The interaction of the vertical fins/canted tail, whatever you want to call it with the vortices shed off the LERX can induce structural fatigue.

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How serious aerodynomic challenge does it present? Canted tails do generate some lift!? Why doesn't Su 35 have them?!
Hmm...maybe the next rendition of the SU-35 will have canted tails...It can't present too much of a challenge as Boeing was able to do it to an even older, less capable design.
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canted tails has a disturbing tendency of suffer severe buffeting, F-22 being a prime example, i dont think they will exist on next gen
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Moving the twin canted tails out wide allows them to be shorter than when mounted on the body. Making them all-moving parts is more efficient yet. The disadvantage of all-moving tail is the loss of prime antenna space.
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Just FYI, I believe the canted tails were taken out of the Silent Eagle design. Aside from improved electronics, the Silent Eagle's only primary difference from the F-15K's and F-15SG's being built now is the Conformal Weapons Bay option as far as I know.
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Add: - fly-by-wire controls - two additional underwing weapons stations - RCS optimization with focus on frontal aspect RCS against X-band radars

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No one to explain corner effect? Cant from cell phone...
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Doesn't the Saudi F-15SA at least add the two extra hardpoints and fly-by-wire controls? The RCS thing is probably correct though.
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I always thought the canted tail fins were a aerodynamic feature as well as helping to reduce the RCS.
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Doesn't the Saudi F-15SA at least add the two extra hardpoints and fly-by-wire controls? The RCS thing is probably correct though.
Yes, that is correct. F-15SA will include FBW, a digital EW suite, AN/AAS-42 IRST, APG-63(V)3 AESA, JHMCS for both cockpits and two additional payload stations. Much of that is very similar to F-15SE systems.

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I always thought the canted tail fins were a aerodynamic feature as well as helping to reduce the RCS.
Any airplane with a tail will have a big RCS when compared to a tailless airplane (i.e. flying wing).

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Any airplane with a tail will have a big RCS when compared to a tailless airplane (i.e. flying wing).
Until the nice tailless plane start to bank. The way you flat turns is more important than having a tail or not. Those are fighters! Sukhoi has shown the new trend. Chengdu (J20) another one (draggy). Lockheed rely to (assisted) conventional aero. Japan is paddling its way into it. Didn't see anything special in the Turkish and Korean project (didn't check back so take this remark as it is!). ... Let's see what's EU will come with... If there is ever one day?
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Is this the latest fad/discovery? What's the principal advantage?...besides looking sexier.
It has a lot to do with eliminating the corner effect and reducing RCS in the horisontal plane. In some cases it can even improve turning.
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The canted tails minimize the need to use the all-moving tails. They also reduce the size or in some cases remove the need for air brakes. With digital controls and electro-hydraulic actuators the limited movements of control surfaces has not only become removed, but the computers will distribute the movements to non-traditional surfaces to gain the best expected net result. And the most advanced systems incorporate emergency control movements with damage recognition to remain flight worthy with what should be catastrophic failure. The only way to reach the goal is combining redundancy and broad distribution. Aligning control surfaces with the x, y, and z planes is not as helpful as being at an angle to the plane as alignment reduces - not increases - redundancy.

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The canted tails minimize the need to use the all-moving tails.
Please explain. It is generally accepted that having an all-moving canted tail comes with advantages over conventional canted, conventional vertical and all-moving vertical.
They also reduce the size or in some cases remove the need for air brakes.
Not because they are canted. vertical tails can perform this function too if desired.
With digital controls and electro-hydraulic actuators the limited movements of control surfaces has not only become removed, but the computers will distribute the movements to non-traditional surfaces to gain the best expected net result. And the most advanced systems incorporate emergency control movements with damage recognition to remain flight worthy with what should be catastrophic failure. The only way to reach the goal is combining redundancy and broad distribution. Aligning control surfaces with the x, y, and z planes is not as helpful as being at an angle to the plane as alignment reduces - not increases - redundancy.
If you are talking about using conventional canted tails to induce a pitch up or pitch down moment, then they can induce a pitch up moment, but not a pitch down moment. The exact same limitation applies to vertical tails. If the canted tails are at a YF-23esque angle at ~45 degrees or similar and are all moving then you can generate useful pitch up and pitch down moments. As for using canted tails to augment roll, vertical tails can perform the exact same function.