How can you analyse one particular component of the plane based on experiences with other completely different designs from different eras, and not on the design philosophy of the actual plane and how that component would interact with the rest of the design?
Why would the Chinese 4th gen need ventral fins? It has relaxed stability in the yaw axis, the directional stability is maintained mostly by the flight control system, the airframe doesn't have to provide as much stability as 3rd gen designs. The incorporation of the ventral fin may simply a lack of confidence in the new flight control.
In the supersonic regime, cross-sectional area is far more important than shape, an aft-fuselage like that of the Su-27 contributes to as much as 40% of the total drag. That's why T-50 have such small rudders, to lower the total cross-sectional area of the aft-fuselage, reducing drag in supersonic flight.
Not really, F-15 and Su-27, like all other 4th gen fighters, are subsonic dog fighters, they suffer serious performance penalties in the supersonic regime, while F-22 and T-50 are designed with manoeuvrability in the supersonic regime in mind, they will easily overcome 4th gen fighters in supersonic dog fights.
The laws of physics remain the same for the J-20, T-50, F-15 or Spitfire.
If you have read about the use of thrust vectoring as a lateral or yaw control you will know that the basic finding of these studies in Russia and the US was that thrust vectoring can be used to control the jet as a regular dorsal fin would do, this meant that the use of thrust vectoring allows for a reduction in size of the vertical stabilizers and rudders, the T-50 follows very well this principle.
The F-22 also uses thrust vectoring as a pitch device thus tailplane deflection is kept at a minimum for supersonic trim and maneouvrability so it does not need canards.
Now you could say the T-50 is really draggy but is not the case; aerodynamically speaking reducing into several independent elements a fuselage makes less drag than creating a huge fuselage as a unit.
That was one of the reasons the Russians opted for podded engines.
The F-18E is a more conventional fuselage but still fails to be as effective as the Su-27 consider both jets only difference in one has buried engines into the fuselage (F-18E) and other podded (Su-27).
Now the flight control system is based upon the aerodynamic of the vehicle not the vehicle upon the flight control, its software is written based upon the aerodynamic properties of the jet.
By using the flight control you are just limiting the aircraft from entring into spins or stalling.
The MiG-29A having simplier flight controls can fly as well as the F-16, this is the result of aerodynamics.
A fighter like the Su-35BM if tracks and detects a stealth fighter can shoot it down, its only disadvantage is it has no stealth so it will be detected first, but in agility and supercruise can fly as well as any other fighter including the F-22.
With stealth you create machines more bulky, fuselages with larger cross section thus more drag, they are not rounded like a missile, which every one knows have circular cross section and conic or ogival nose tips.
The Russians understood that so they created a fighter with a small nose with wing and fusleage blended so its volume uses that space for weapons bays.
the problem for the chinese and americans is they wanted something with a trapezoidal cross section , that is not really very aerodynamic, and they know it
The F-35 has for that reason a rounded nozzle, which is shielded by the booms that carry the tailplanes and vertical tails.
A F-15 flying clean has excellent performance and the same is for the Su-27 but when you add external fuel and weapons you increase detectability.
The MiG-31 has semi recessed weapons this is the relatively ideal configuration for drag up to some degree but it is bad for stealth, in fact small cross sections are better than large but stealthy.
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Now thrust vectoring also is not something that increases agility a lot as many think, on a turn it will give gains of only 10-15% or 1-2 more degrees a second.
So basicly thrust vectoring only can be used a a post stall device or a yaw or pitch control.
Canards are not the miracle device many think, the J-20 uses a very conventional wing and canard, needs ventral fins due to lack of control laterally due to very small dorsal fins.
About transonic and supersonic agility, in reality it is mostly useless, as speed increases the ability of an aircraft to turn drops abruptly, a fighter like the MiG-31 will turn at 7 degrees/s at Mach 1.2 and 3 degrees at Mach 1.8.
So even the F-22, J-20 or T-50 can not scape a missile turning because first they have a human who won`t resist turns of 50Gs as a missile does so basicly supersonic turning is myth that is the reason the americans are making UCAVs and England is doing the same.
Supercruise only brings the ability to fly fast and thus out run opponents.
The J-20 therefore uses canards just to keep the shift of its lift center at supersonic in check and reduce its effects.
The T-50 also has LEVCONs that basicly are moveable LERXs. a LERX does the same a canard does it keeps the shift of center of lift more limited.
