Chengdu J-20 news and analysis Part III

[overscan (PaulMM)]

Removed off-topic posts. Geopolitical opinions on China are off-topic, as are insults to other forum members.

 

[Trident]

The bits that can be, and are kept secret, or that are just plain hard to copy, are (1) the parts and materials on the inside of the mold line and (2) how things are made. The former category (in the case of a stealth airplane) includes RAM, seals, how doors work, apertures &c. The latter category includes the art of achieving a very accurate OML.

In the J-20, we just don't know how many of these design challenges were met by engineering, or even reverse-engineering from the OML, and how many solutions were significantly aided by espionage. We do know that Chengdu and the PLA customer had to be pretty confident that solutions were within reach before the big tide of cyber stuff started rolling in, with the help of Australian and other braggarts.

From the first paragraph it also follows that (since the information source available to us is pretty much limited to photography) we can't even, strictly speaking, be certain whether the challenges were successfully met at all.

 

[TAKHISS]

A new PV suggests carrier-based J-20 fighters
https://www.youtube.com/watch?v=RgKOOz5_5FU

 

[sferrin]

And X-47s too. :

 

[overscan (PaulMM)]

https://www.sinodefenceforum.com/j-20-5th-gen-fighter-thread-vi.t8169/page-360

 

[sferrin]

Love the J-20. After all the canard-ATF concepts back in the 80s I expected something like this to be the result. Was disappointed in the "modern F-15" looking F-22. (The F-23 did take my breath away though.)

 

[siegecrossbow]

Not as good as J-10B TVC but still cool considering that it still uses interim Russian engines.

https://www.youtube.com/watch?v=UVG_I8Ywenw

 

[Ares]

https://imgur.com/zNhH8J2

DARPA : Cool idea isn't it?

Airbus : I have the same idea

China : It's my idea now

 

[sferrin]

https://imgur.com/zNhH8J2

DARPA : Cool idea isn't it?

Airbus : I have the same idea

China : It's my idea now. And I'm flyin' it tomorrow.

Fixed.

 

[sublight_]

Somebody correct me if I am wrong here..... But when I watch an f22 fly it's incredibly stable with no wiggle at all, but after looking at the footage of these beasts, they seem to look like they are barely hanging in there, with a constant shake throughout the turns. Anybody else seeing this?

 

[latenlazy]

Somebody correct me if I am wrong here..... But when I watch an f22 fly it's incredibly stable with no wiggle at all, but after looking at the footage of these beasts, they seem to look like they are barely hanging in there, with a constant shake throughout the turns. Anybody else seeing this?

I’ve noticed for a while now. I wouldn’t characterize it as barely hanging in there. It looks looks like relative to where the stick wants to go they’re overturning. I figured it’s either because at lower speeds they’re aerodynamically unstable (for anyone who read the J-20’s original design study this shouldn’t come as a surprise, the designers really loosened up the static margins), or alternatively the stick is just really sensitive. I think in the F-22 a bit of that stability is also probably aided by small adjustments from the TVC.

 

[overscan (PaulMM)]

Somebody correct me if I am wrong here..... But when I watch an f22 fly it's incredibly stable with no wiggle at all, but after looking at the footage of these beasts, they seem to look like they are barely hanging in there, with a constant shake throughout the turns. Anybody else seeing this?

Doesn't really jump out at me, but its possible the FBW software needs some more tweaking, and F-22 has a better thrust/weight ratio and thrust vectoring. The J-10B with TVC is probably a better comparison.

 

[sferrin]

for anyone who read the J-20’s original design study

Is this online anywhere? (Or is it in Deino's book?)

 

[latenlazy]

for anyone who read the J-20’s original design study

Is this online anywhere? (Or is it in Deino's book?)

https://defence.pk/pdf/threads/translation-of-j-20-article-by-dr-song-wencong.165231/

We translated the original article in SDF years ago...think around 2012?

 

[sferrin]

Thanks!

 

[TomcatViP]

lightened airframe. Either they took the Zero road, either this thing has no military system and it's just an airshow freak.

But don't take me wrong. This is impressive (enough).

 

[sferrin]

lightened airframe. Either they took the Zero road, either this thing as no military system and it's just an airshow freak.

But don't take me wrong. This is impressive (enough).

You talking about the J-10 or the -20?

 

[Blitzo]

lightened airframe. Either they took the Zero road, either this thing as no military system and it's just an airshow freak.

But don't take me wrong. This is impressive (enough).

You talking about the J-10 or the -20?

neither makes much sense tbh.

J-10 was already a fairly nimble plane to begin with and giving it TVC "only" gives it the same kind of performance that other maneuverable TVC equipped fighters have demonstrated.

What J-20 performed at the airshow this time around was also nothing too new compared to what we've gotten hints of over the years.

 

[overscan (PaulMM)]

https://defence.pk/pdf/threads/translation-of-j-20-article-by-dr-song-wencong.165231/

Abstract: This paper analyzes the main design conflicts of the future fighter's stealth, high maneuverability, and supercruise characteristics while proposing specific design solutions for trans-sonic lift to drag characteristics, low speed high AOA characteristics, and supersonic drag characteristics. The author believes that in-depth study of fluid dynamics, exploration of the full practical potential of current aerodynamic designs, development of new design concepts, employment of corresponding systematic and control measures, and necessary compromise among numerous design proposals will allow us to achieve our design goals.

1. Introduction:
The future fighter, aside from satisfying low and mid-altitude maneuverability performance of modern 4th gen. fighters, must have the capability to supercruise and perform unconventional maneuvers such as poststall maneuvers. As a result, the aerodynamic configuration of the future fighter must not only satisfy the design constraints of RCS reduction but also lower supersonic drag, improve lift characteristics, and improve stability and controllability under high AOA conditions whilel accounting for trans-sonic lift to drag characteristics. The high number of design requirements provide new challenges to the aerodynamic layout. The design must employ new aerodynamic concepts and approaches, take necessary systematic and control measures, and compromise amongst the numerous design points in order to obtain the necessary design solution.

2. Main design conflicts:

The design requirement for stealth brings new difficulties to the aerodynamic design. Frontal stealth capability imposes new restrictions on both the sweep angle of the leading edge and air intake configuration. Lateral stealth requires the proper alignment of the aircraft's cross sectional shaping and the vertical stabilisor configuration. These restrictions and requirements must be considered during the earliest phase of designing the aerodynamic configuration.

Trans-sonic lift to drag ratio and supersonic drag are traditional design conflicts. Modern Fourth gen. fighters successfully solved this dilemma by relaxing aircraft stability and employing wing bending mechanisms. Future fighters, however, have stricter requirements for supersonic drag characteristics. At the same time, conventional design maximizing low speed lift characteristics contradicts the pursuit for lower supersonic drag. Since current aerodynamic measures don't offer satisfactory solutions to these conflicts the design team must explore new design paths.

Post stall maneuvers require the aircraft to have good controllability and stability. After the plane enters the post stall region, however, the decrease in stability and control efficiency of conventional rudder surfaces become irrecoverable. One must carefully design an aircraft to enable sustained controllability at high AOA. Although it is possible to solve the problem of post-stall controllability through the use of thrust vectoring nozzles, the aerodynamic configuration itself must provide enough pitch down control capability to guarantee the aircraft to safely recover from post-stall AOA should the thrust vectoring mechanism malfunction. As a result, it is vitally important to study unconventional aerodynamic control mechanisms for high AOA flights.

3. Trans-sonic lift to drag characteristics

Trans-sonic lift to drag characteristics determine an aircraft's maximum range and sustained turn capability. The future fighter's demands for these characteristics will exceed those of modern 4th gen. fighters. Modern fighters employ the strategies of relaxing longitudinal stability, adapting wings with medium sweep and aspect ratio, twisting the wing, and adding wing-bending mechanisms to greatly improve the lift-to-drag characteristics. Due to the future fighter's requirement for supercruise, supersonic drag characteristic is a critical design point and designers must avoid using aerodynamic measures that may potentially increase supersonic drag. As a result, the wing shape and wing twist coefficient can't be selected based on trans-sonic lift to drag characteristics alone. It is necessary to employ wing-bending mechanisms but its aerodynamic efficiency has already been exhausted.

Further decreasing the aircraft's longitudinal relaxed stability is an excellent solution to this problem. Diagram 1 shows how the variation tendency of trim-drag coefficients against longitudinal instability of a conventional fighter aircraft in a tight, sustained turn. Modern fighters fix their longitudinal instability at 3% the average aerodynamic chord length. The future fighter could enjoy a significant improvement in lift-to-drag if the longitudinal instability could be increased to a magnitude of around 10%.

Further relaxing the longitudinal instability could not only enhance trans-sonic lift to drag characteristics but also improve super sonic lift to drag capabilities, increase take-off and landing characteristics, and maximize low-speed lift characteristics. This is akin to killing three birds with a single stone. Yet a increase in longitudinal instability will also increase the burden on high AOA pitch down control and subsequently increase flight control complexities. As a result the design team should not "over-relax" the longitudinal stability.

4. Low speed high AOA characteristics

4.1 Lift-body LERX Canard configuration

Advanced modern fighters utilized research on detached vortices from the 1960s and 70s to gain excellent lift characteristics with their max lift coefficient peaking at around 1.6. They either employ conventional LERX configuration or canard configuration to accomplish this. The future fighter has higher requirements for max lift coefficient and the situation is further complicated by the fact that the use of twin vertical stabilizers is detrimental to lift (see figure 4.2). As a result the design team must raise the max lift coefficient to a whole new level. It will be difficult to realize this goal simply employing conventional LERX configuration or canard configuration.

It is beneficial to choose canard configuration from a high AOA pitch down control stand point(see figure 4.3). Blending lift body LERX characteristics with the conventional canard configuration to form a "lift body LERX canard configuration" will greatly enhance the max lift characteristics. Exploration of the lift body LERX canard configuration will solve three important technical issues. The first problem is the aerodynamic coupling between canards and medium sweep, medium aspect ratio wings. The second problem is the coupling between the canards, the LERX, and detached vortices generated by the wings. The third problem concerns the gains and losses of employing body lift on a canard configuration aircraft.

Traditionally close coupled canard configuration aircraft utilize constructive coupling between the canards and detached wing vortices to enhance the max lift coefficient. Only wings with large back-sweep angle and small aspect ratio could generate detached vortices that are powerful enough for the task. As a result most modern canard configuration fighter aircraft have a leading edge backsweep angle of around 55 degrees and an aspect ratio of around 2.5. For these aircraft, the canards could generate around a 3 to 4 times increase in max lift coefficient with respect to their wing areas. Ideally we hope to employ wings with medium leading edge backsweep angle and medium aspect ratio in order to improve lift characteristics over the entire AOA range. This wing shape, however, could not effectively generate leading edge detached vortices. Could the canards still attain their original lift enhancing effects? The answer is yes according to wind-tunnel tests. As the slope of the aircraft's lift curve increases, the lift enhancing capabilities of the canards are the same as those on traditional close coupled canard configuration aircraft (see figure 2). The key influence on aerodynamic coupling between the canards and medium back-sweep, medium aspect ratio wings should not be interference among detached vortices. Preliminary studies indicate that down-wash on the wings generated by the canards play a far greater role.

It is a well known fact that LERX could improve the max lift characteristics on medium back sweep, medium aspect ratio wings. In order to obtain even better lift characteristics, we should consider using both canards and LERX to create a canard-LERX configuration. Study shows that employing both canards and LERX not only retain the lift enhancing effects of the two mechanisms when they are used separately but also help achieve higher lift-coefficient (see figure 3). This means that there is beneficial coupling among the canards, LERX, and the wings.

Blended wing lift body configurations could utilize lift generated by the aircraft's body to increase internal load and enhance stealth characteristics at relatively low costs to drag. Lift-body configurations have been adapted by many conventional configuration aircraft and achieved excellent results. Yet until now now canard configuration fighter utilized lift-body configuration. This isn't because aerodynamic experts failed to realize the tremendous advantage of the lift body configuration but the result of a canard configuration aircraft's need to place the canards above the aircraft's wings. It is difficult for lift-body configuration aircraft to satisfy this demand. Our experimental results indicate that although the canards on a canard-LERX configuration aircraft employing lift-body suffered a decrease in lift-enhancing effects, the overal lift characteristic of the aircraft was still superior to that of a canard-LERX aircraft not employing lift-body (see figure 4). Figure 5 shows the vortex generation on the wings and body of a lift-body canard configuration aircraft observed using laser scanning. It demonstrates that planes employing this configuration derive excellent lift characteristics not only from coupling among the canards, LERX, and detached vortices but beneficial interaction between the left and right detached vortices. The latter contribute to significant lift on the body of the plane and greatly contributed to the enhancement of lift characteristics. Figure 5 also indicates that the detached vortices primarily contribute to lift on the body and inner portions of the wings. Consequently, most of the lift produced under high AOA conditions are generated in the corresponding areas.

4.2 Canted vertical stabilizers

Vertical stabilizer design is an important consideration when it comes to future fighter configuration design. From a lateral stealth stand point, the vertical stabilizers should cant inward or outward to reflect incoming radar waves in other directions. The future fighter must be long and thin to accommodate for supercruise and as a result, the space between the vertical stabilizers couldn't be too wide. The twin stabilizers should cant outward in order to decrease destructive interference between the vertical stabilizers. Since the future fighter will fully utilize detached vortices to improve max lift coefficient, forward vortices will generate relatively high outward facing velocity airflow on the vertical stabilizers. Figure 6 shows the calculation results of a type of lift body LERX canard configuration fighter using n-s time average function. It indicates the limiting flow rate on the aircraft's rear once the vertical stabilizers are removed. The results indicate that the regional side slip angle at the location where vertical stabilizers are usually installed reaches around 15 degrees when the AOA is 24 degrees and the side slip angle is 0 degrees. If the back-sweep angles of the vertical stabilizers are sufficiently large, the enormous regional side slip angles could generate leading edge shed vortices on the external faces of the stabilizers and form low pressure regions. Regional sideslip angles will also increase the static pressure on the inner portions of the vertical stabilizers. As a result, the vertical stabilizers will become highly efficient lateral force surfaces which direct the lateral forces outwards. The lateral forces are projected in the direction of lift, with respect to the outward canting vertical stabilizers, and generate negative lift. Negative lift acting on the vertical stabilizers and rear body will both contribute to the undesirable pitch up torque. The high pressure region between the vertical stabilizers will form adverse pressure gradients on the body of the plane and negatively impact the stability of leading edge detached vortices. Since the vertical stabilizers are already highly loaded at 0 degree side slip angle, the yaw/roll stabilization efficiency of the vertical stabilizers will be decreased.

The negative impacts of vertical stabilizers as described above are closely associated with lift-enhancing measures and are, as a result, difficult to root out. Yet adjustment of the vertical stabilizer’s area, position, cant angle, and placement angle and improvement measures such as making slots on the rear body can minimize the negative impact of the vertical stabilizers. Ordinarily, the max lift reduction coefficient generated by the vertical stabilizers could reach around 0.4. We’ve managed to successfully lower it below 0.1 through experimentation.

Decreasing the vertical stabilizers’ area or even employing tailless configuration are directions worth studying. Their significance not only include improving low speed high AOA performance but also help improve stealth characteristics, lower drag within the entire flight envelope, decrease weight, and reduce cost. Implementing the tailless configuration requires the tackling of three major technical difficulties: replacing the stabilizers with another yaw control mechanism, installing sensitive and reliable side slip sensors, and implementing new flight control technology. As of now, these difficulties are being tackled one at a time. Relatively speaking, decreasing vertical stabilizers’ area and relaxing static yaw stability are more realistic options. Generally speaking, the relative size of the vertical stabilizers is around 20% to 25%. In or studies, utilizing all moving vertical stabilizers with 10% to 13% could still maintain basic yaw stability while retaining the vertical stabilizers’ function as yaw control mechanisms.

4.3 Aerodynamic control mechanisms

The requirement for high AOA pitch down control capability is closely related to the longitudinal static instability requirement. The greater the longitudinal static instability, the higher the demands for pitch down control capabilities. As described in chapter 3, the future fighter will hopefully increase its longitudinal static instability to around 10% its average aerodynamic chord length to enhance the trim's lift to drag and lift characteristics. As a result there should be a corresponding improvement in the pitch down control capability. We can categorize two types of control surfaces based on the relative position of the pitch control surfaces with respect to the aircraft's center of mass: positive load pitch down control surface and negative pitch down control surface. Control surfaces placed behind the center of mass, including the vertical stabilizers and trailing edge flaps, generate pitch down control torque by increasing lift. They are considered positive load control surfaces. Control surfaces placed in front of the center of mass, like the canards, are negative load control surfaces. Since the main wing's ability to generate lift tends to saturate under high AOA conditions, the positive load control surfaces' pitch down control capabilities tend to saturate under high AOA as well. Therefore it will be wise to employ negative load control surfaces for pitch down control under high AOA conditions. Figure 7 compares the pitch down control capabilities of the canards and horizontal stabilizers. From the high AOA pitch down control stand point, it will be wise to use canards on the future fighter. Canards on close coupled canard configuration aircraft have relative short lever arms. Employing the LERX canard configuration can increase the canards’ lever arms while retaining the benefits of positive canard coupling. Considering the overall lift enhancement effect and pitch down control capabilities, we can set the canards’ maximum relative area to around 15% and the maximum canard deflection to 90 degrees.

Yaw control ability under high AOA is another noteworthy problem. Control surface efficiency deteriorate rapidly with an increase in AOA for tailless and even conventional configuration fighters. Therefore it is necessary to consider control mechanisms other than conventional control surfaces. Studies on differential LERX, drag rudder, differential wingtips, and all moving vertical stabilizers indicate that differential LERX and drag maintained relatively high yaw control efficiency under high AOA conditions (see figure 8).

5. Supersonic drag characteristics

The key to lowering supersonic drag is to minimize the max cross sectional area of the aircraft.Accomplishing this requires excellent high level design skills. Placement of the engines, engine intakes, landing gears, cartridge receiver, weapons bay, and main structural support all influence the max cross sectional area of the aircraft. Attention to details and careful considerations are necessary to design decision making.

Wingshape has profound effects on supersonic drag characteristics. Small aspect ratio wings with large backsweep have low supersonic drag but are detrimental to low speed lift and trans-sonic lift to drag characteristics. If we select the liftbody LERX canard configuration we can expect to retain relatively good lift to drag characteristics while using medium backsweep wings. Under high AOA conditions, liftbody LERX canard configuration aircraft concentrate lift on the body and inner portions of the wings so moderately lowering the aspect ratio will not only not lower the max lift coefficient but raise it (see figure 10). Because of this, employing small aspect ratio wings on a lift-body LERX canard configuration aircraft will settle the conflicts among supersonic drag characteristics, low speed lift characteristics, and trans-sonic drag characteristics.

6. Air Intake design

Air intakes are one of three major sources of radar scattering. In order to lower intake radar reflection area, the design team must place a series of limitations on intake design due to stealth considerations. These limitations will significantly influence intake aerodynamic design.

Caret intakes have oblique intake openings and fixed intake ramps and could effectively lower radar cross section and structural weight. The future fighter may implement this technology. Preliminary studies indicate that when compared with conventional adjustable intakes, Caret intakes' total pressure recovery coefficient surpasses its conventional counterpart in supersonic and trans-sonic regimes and is only slightly lower in the low-subsonic regime. It also offers excellent total pressure distortion performances. Radar absorbing deflectors minimize the air-intake's radar reflection and could significantly improve its stealth characteristics. Aerodynamically speaking, the radar absorbing deflectors would slightly decrease the overall pressure recovery and flow coefficients but have no ill-effects on static or dynamic distortion coefficients.

7. A comprehensive study of a design example

The design team made a future fighter proposal based on the points raised by this article. The proposal employs lift-body LERX canard configuration. It is unstable in both the lateral and yaw directions. The proposal employs small aspect ratio wings with medium back sweep angle, relatively large dihedral canards, all moving vertical stabilizers far smaller than those on conventional fighter aircraft, and S-shaped belly intakes. According to our assessment, the proposed aircraft will have excellent supersonic drag characteristics, high AOA lift characteristics, high AOA stability and controllability, and excellent stealth characteristics.

8. Conclusion

The aerodynamic design for the future fighter, compared with that of advanced modern fighters, will require more design features and subsequently pose greater challenges. Only in-depth study of fluid dynamics, exploration of the full practical potential of current aerodynamic designs, development of new design concepts, employment of corresponding systematic and control measures, and necessary compromise among numerous design proposals will allow us to achieve our design goals.

 

[siegecrossbow]

lightened airframe. Either they took the Zero road, either this thing as no military system and it's just an airshow freak.

But don't take me wrong. This is impressive (enough).

The chief designer confirmed in an interview that all three J-20s used during the aerial display are units from an operating squadron, so I doubt that they removed the military system just for the airshow. It is possible that they've reduced the fuel load.

 

[latenlazy]

lightened airframe. Either they took the Zero road, either this thing as no military system and it's just an airshow freak.

But don't take me wrong. This is impressive (enough).

The chief designer confirmed in an interview that all three J-20s used during the aerial display are units from an operating squadron, so I doubt that they removed the military system just for the airshow. It is possible that they've reduced the fuel load.

Or maybe that the current variants are just lighter than what a lot of people might think.

 

[siegecrossbow]

https://defence.pk/pdf/threads/translation-of-j-20-article-by-dr-song-wencong.165231/

Hey I've translated that over 7 years ago!

 

[latenlazy]

https://defence.pk/pdf/threads/translation-of-j-20-article-by-dr-song-wencong.165231/

Hey I've translated that over 7 years ago!

Yep. You helped jumpstart the process that got the rest of us all scouring for more detailed Chinese sources. Take a bow!

 

[overscan (PaulMM)]

https://defence.pk/pdf/threads/translation-of-j-20-article-by-dr-song-wencong.165231/

Hey I've translated that over 7 years ago!

Yep - it might have been posted before, but its an interesting read. Here's the original article in Chinese. Note - it's from 2001, but it exactly describes the J-20 aerodynamic configuration.

 

[latenlazy]

Yep - it might have been posted before, but its an interesting read. Here's the original article in Chinese. Note - it's from 2001, but it exactly describes the J-20 aerodynamic configuration.

Which shouldn't come as a surprise. The author of the study was the designer of both the J-10 and the J-20.

 

[overscan (PaulMM)]

I am fully aware who Song Wencong was, its just a little surprising it was published in 2001.

 

[Blitzo]

I am fully aware who Song Wencong was, its just a little surprising it was published in 2001.

Out of interest, is it surprising because 2001 is early or late?

 

[latenlazy]

I am fully aware who Song Wencong was, its just a little surprising it was published in 2001.

Out of interest, is it surprising because 2001 is early or late?

I think what Paul is saying is that he’s surprised the aerodynamic concept preceded what would become the J-20 by a decade. Given where Chinese aerospace was at that time I suppose that surprise is pretty understandable. (Correct me if I misunderstood or am wrong here of course).

 

[sferrin]

I am fully aware who Song Wencong was, its just a little surprising it was published in 2001.

Out of interest, is it surprising because 2001 is early or late?

I think what Paul is saying is that he’s surprised the aerodynamic concept preceded what would become the J-20 by a decade. Given where Chinese aerospace was at that time I suppose that surprise is pretty understandable. (Correct me if I misunderstood or am wrong here of course).

On the other hand, that general configuration was not only in open literature at the time, it was actively being worked in other countries.

 

[sferrin]

Don't know if this has been mentioned yet:

"Song Zhongping, a military expert and TV commentator, said that the J-10B is a demonstrator aircraft with a highly important mission as it's not only testing the thrust-vectoring WS-10 Taihang engine for J-10B, but also testing it for J-20A, an aircraft that is in development and yet to be revealed and is more advanced than the J-20. "

http://www.defense-aerospace.com/articles-view/release/3/197368/j_20-and-j_10b-fighters-dazzle-spectators-at-china-airshow.html

 

[Sundog]

Something interesting to note with the Lockheed JAST design is the canards weather-vane at subsonic speeds and became "active" at supersonic speeds, to minimize trim drag and increase supersonic maneuverability. It reminds me of the XP-55 in that regard; in the sense that the XP-55s elevator (It wasn't a canard to me, as in my engineering reference it doesn't supply lift to help support the weight. But it may look like a duck in flight, so take your pick. ) weather vaned statically, but became a lifting surface dynamically in pitch, making it dynamically unstable, while maneuvering. In theory anyway, it didn't quite work out that way in practice due to friction/lag in the flight control system.

Still, until recently, I had no idea how advanced the flight control system was designed to be in the XP-55; statically stable in cruise, and unstable in maneuver. The best of both worlds, unsuccessfully, until the F-16 showed up.

 

[TomcatViP]

The chief designer confirmed in an interview that all three J-20s used during the aerial display are units from an operating squadron, so I doubt that they removed the military system just for the airshow. It is possible that they've reduced the fuel load.

Once we heard that the J-31 was a production ready fighter... and then we were graced to see it barely able to fly (still have compassion for that poor pilot kicked out on the ramp and ordered to demo the thing in flight).

 

[overscan (PaulMM)]

I am fully aware who Song Wencong was, its just a little surprising it was published in 2001.

Out of interest, is it surprising because 2001 is early or late?

I think what Paul is saying is that he’s surprised the aerodynamic concept preceded what would become the J-20 by a decade. Given where Chinese aerospace was at that time I suppose that surprise is pretty understandable. (Correct me if I misunderstood or am wrong here of course).

Not at all. I'm just surprised the article was published openly that long ago, when presumably the 'J-XX' program was classified. Even in the West, articles on aerodynamic development of an actual aircraft configuration like F-16 was generally published only after the prototype flew. In 2001 even J-10 was still pretty secret. I guess this was more in the nature of generic research at that time.

 

[latenlazy]

I am fully aware who Song Wencong was, its just a little surprising it was published in 2001.

Out of interest, is it surprising because 2001 is early or late?

I think what Paul is saying is that he’s surprised the aerodynamic concept preceded what would become the J-20 by a decade. Given where Chinese aerospace was at that time I suppose that surprise is pretty understandable. (Correct me if I misunderstood or am wrong here of course).

On the other hand, that general configuration was not only in open literature at the time, it was actively being worked in other countries.

I don’t see any LERXes.

 

[sferrin]

I am fully aware who Song Wencong was, its just a little surprising it was published in 2001.

Out of interest, is it surprising because 2001 is early or late?

I think what Paul is saying is that he’s surprised the aerodynamic concept preceded what would become the J-20 by a decade. Given where Chinese aerospace was at that time I suppose that surprise is pretty understandable. (Correct me if I misunderstood or am wrong here of course).

On the other hand, that general configuration was not only in open literature at the time, it was actively being worked in other countries.

I don’t see any LERXes.

"that general configuration" Obviously not identical but very similar.

 

[Blitzo]

I am fully aware who Song Wencong was, its just a little surprising it was published in 2001.

Out of interest, is it surprising because 2001 is early or late?

I think what Paul is saying is that he’s surprised the aerodynamic concept preceded what would become the J-20 by a decade. Given where Chinese aerospace was at that time I suppose that surprise is pretty understandable. (Correct me if I misunderstood or am wrong here of course).

On the other hand, that general configuration was not only in open literature at the time, it was actively being worked in other countries.

Not particularly relevant unless we think that every single twin tail canard delta at the time was supposed to have a bearing on the paper.

 

[Blitzo]

The chief designer confirmed in an interview that all three J-20s used during the aerial display are units from an operating squadron, so I doubt that they removed the military system just for the airshow. It is possible that they've reduced the fuel load.

Once we heard that the J-31 was a production ready fighter... and then we were graced to see it barely able to fly (still have compassion for that poor pilot kicked out on the ramp and ordered to demo the thing in flight).

I don't think anyone said FC-31 was production ready? Rather that it could be produced within a few years if a customer was interested in it.

Being production ready also has nothing to do with how it performs... considering in FC-31's case it was underpowered, and they likely wouldn't have been cleared to show anything near its full envelope even when underpowered as well.

 

[sferrin]

I am fully aware who Song Wencong was, its just a little surprising it was published in 2001.

Out of interest, is it surprising because 2001 is early or late?

I think what Paul is saying is that he’s surprised the aerodynamic concept preceded what would become the J-20 by a decade. Given where Chinese aerospace was at that time I suppose that surprise is pretty understandable. (Correct me if I misunderstood or am wrong here of course).

On the other hand, that general configuration was not only in open literature at the time, it was actively being worked in other countries.

Not particularly relevant unless we think that every single twin tail canard delta at the time was supposed to have a bearing on the paper.

Did I say "every single twin tail canard"? No. I did not.

 

[overscan (PaulMM)]

The article describes a very specific aerodynamic configuration where the LERX and canard work together to increase maximum lift higher than either in isolation, and higher than the F-22 configuration.

it also reduces wing sweep to a moderate value which improves lower speed performance as well as moving the wing backward, allowing more room for a centrally located weapons bay.

It also describes all-moving vertical tails, angled out, and even shows a rough drawing of the rear fuselage showing the extended tail fairings. Its not a generic canard delta configuration by any means. This is a fix to some aerodynamic downsides of the J-10 configuration and an attempt to create a configuration that outmaneuvers the F-22/Eurocanards.

The fact it retained the canard implies that maneuverability remained of prime importance after 2001. Its an air superiority aircraft with secondary interceptor/strike roles.

 

[Blitzo]

Did I say "every single twin tail canard"? No. I did not.

Ah good, then you agree that referencing the JAST canard delta proposal and comparing it to Song's aerodynamic proposal (that became J-20) is illogical. Glad that's settled.

===

In all seriousness, when you said "general configuration" the only logical way to interpret it is to believe that you mean twin tail canard delta configurations.