Chengdu J-20 pictures, analysis and speculation Part I

[saintkatanalegacy]

The NATF-23 had different shape canards and the CALF also had the same rhomboid low aspect canards, on the MiG-1.44 the canards were also huge but it had TVC nozzles so as the F-22 canard deflections were not going to be the main way to stabilize the MiG and the MiG-1.44 also had flaps on the booms to work as tailplanes as pitch control, these are absent on the J-20.
The MiG also has dogtooth to re-energize the canard and create vortices, on the J-20 this is absent.
The T-50 has ommited completely the canard and the MiG 1.44 was cancelled deemded as not the best way to achieve stealth and supercruise

errmm...

are you sure J-20 canards won't create vortices as they deflect?

 

[dingyibvs]

see the J-10 looks dwarfted and the J-20 canards look huge.
If canard deflections are not desired due to drag and higher RCS then why adding huge canards to an aircraft which already is big

Isn't it obvious? The canards are useful for short TO/Landing and for dogfighting, during which time radar stealth is unnecessary. What's the point of asking such a stupid question? Are you actually interested in some technical discussions or are you only interested in putting down the J-20?

 

[Ogami musashi]

I am not taking to the extreme, no i am taking to the real life conditions, no one will make a Tu-160 or B-1B a dogfighter, the real issues of drag, thrust and structure will simply render the aircraft unpractical.

If you want to take it to extreme....The only reason a Tu-160 would not make a good dogfighter is because of too high wing loading (hence posing structural problems) and no engine with enough thurst available.
Apart from that, you could design a plane that big with good enough turn rates.
When the F-15e strike eagle was introduced and fitted with the original F15C engines, because of augmentation in wing loading and drag (and i recall that the F-15 is of the same size than the C only heavier) they found out being out climbed and out accelerated in dry thrust by.....a 747....

Other issues are aircraft have AoA limits due to stall, some configurations are better to retain lift than others and the canard delta does not have anything special that one with tailplanes, LERX and trapezoidal wings would not offer, and the example still is the Su-27 that has post stall ability at an AoA of 120 deg while other designs with canards do not.

No no; the SU-27 has no post stall ability at 120°; It can go through an AOA range where it would be out of control thanks to its horizontal stabilizator arm lever and can go to 120° because the integral design is assymetric flow relatively free;
When there, the pilot has to play with assymetric thrust to keep the plane in line and the horizontal stab will bring it back just by giving the impulse; All the rest is pure inertia there's no control there I.E the pilot can't stop the nose down back movement even less re increase the AOA.

The J-20 also is within the size of strikers like Su-24, Su-34 and and F-111 and MiG-25BR

The mig-25 is within dimensions of F-22 and F-15
The SU-34 is within dimensions of SU-27
The F-111 and SU-24 are just a bit longer;

So..you have plane of the same take off weight, roughly same dimensions, and two of them are of the dimension of agile and maneuverable fighters (the mig-25 and SU-34)...so as you see the only paramater there changing is....the wing loading.




Excuse me but for now, you haven't provided any real physics facts only your own opinion with vague arguments; As aerofranz posted, you see you have equations for modelizing plane's performance and you can see in them that:

1/there's no weight alone effect (it is the win loading)
2/there's no "canard" or "TVC" or whatever term into the equations..only final parmaters; what counts is the integral design of the plane; That's how you do fluid mechanics studies over a plane, integration of local fluids properties;

 

[overscan (PaulMM)]

Exactly so. The Mikoyan MFI configuration was tested to 60 deg AOA, which is about 30 deg higher than the Su-27 series can sustain.

I believe the 2001 Song Wencong paper describes an unstable canard delta design with two small all moving fins and high AOA capabilities. Of course, that doesn't mean J-20 is necessarily designed for agility...

 

[PAK FA]

No no; the SU-27 has no post stall ability at 120°; It can go through an AOA range where it would be out of control thanks to its horizontal stabilizator arm lever and can go to 120° because the integral design is assymetric flow relatively free;

I disagree with you post stall is the ability of flying in AoA beyond the lifting capacity of the wing, once the wing has stalled as such the Su-27 has post stall ability.
The Su-27 becomes very unstable at 60 degrees of AoA, so for a Su-27 once it passes the 60 degrees mark simply will stall its wing, however because the Su-27 has vortex hysteresis, good lateral control and its tailplanes still have control at 120 degrees of AoA, the aircraft can fly for a very brief time at the post stall regime.
The F-22 also has good lateral control, its TVC nozzles are only at pitch, but its chines forebody vortices keep it stable even at 120 degrees of AoA, so it is very stable at yaw.
I do not know if it can use its tailplanes as well as the Su-27 and if its vortex hysteresis behaves as well as on the Su-27, i do not know if it uses TVC to return to level flight but i can asure you it has good lateral control, because even the F-5 was flown without vertical tail and was found its forebody to keep the jet stable at yaw

 

[overscan (PaulMM)]

PAK FA, you clearly don't have the knowledge to back up your arguments. You are done in this discussion.

 

[Ogami musashi]

I disagree with you post stall is the ability of flying in AoA beyond the lifting capacity of the wing, once the wing has stalled as such the Su-27 has post stall ability.

Post stall refers to controlability of a plane once the lift of the wing is not sufficient to maintain level flight

And in the case of the SU-27 :

The Su-27 becomes very unstable at 60 degrees of AoA, so for a Su-27 once it passes the 60 degrees mark simply will stall its wing

the SU-27 certainly stall far before 60° AOA...actually the SU-27 stalls at 27,5° while the SU-33 stalls at 30° AOA.

however because the Su-27 has vortex hysteresis, good lateral control and its tailplanes still have control at 120 degrees of AoA, the aircraft can fly for a very brief time at the post stall regime.

I have already discussed that point, and this is wrong. There's no control or whatsoever, the SU-27 can stay in straight line and not depart in spin because of absence of assymetric flows...this is a the only reasno why a plane departs and stays spinning; The plane has no control whatsoever, the pilot can only go back to original position and can't stop, accelerate or slow down the movement.
The trajectory of the plane is neither controlable; it is a ballistic trajectory which means the plane has no sufficient force to change its motion.

For once, the SU-27 has no post stall capacity; The viggen can also pull a cobra (with no Lerx, no tailplane or whatsoever...in case you didn't understand yet..a plane is not a lego) but will stall like many.
Many planes were put into similar "post stall" AOA without developping spins, like the F-14 for example which was tested at 74° AOA with weapons...nobody would ever dare to say the plane has post stall control;

The rafale was also tested at 100° AOA + and similarly didn't exhibit any spin departure...

There's a big difference between being able to alter the trajectory or attitude of your plane, and going to a certain attitude; from 30° AOA onwards the SU-27 is totally stalled with most of the control surfaces totally stalled too.

The F-22 also has good lateral control, its TVC nozzles are only at pitch, but its chines forebody vortices keep it stable even at 120 degrees of AoA, so it is very stable at yaw.

You should really read a bit of fluids mechanics, or simplier look at CFD. Chines are at the foremost part of the plane..They can only have an initial cascade effect I.E their role is to energize the secondary vortex created by strakes, lerx and wing LE..
Thus, and as i tend to be a bit annoyed to repeat it over and over, this is not the chines that allow the plane to be stable..but the fact the plane doesn't develop assymetric flow over its length.

I don't know how to make you understand that flows do not travel instantly nor independantly over a plane..

I do not know if it can use its tailplanes as well as the Su-27 and if its vortex hysteresis behaves as well as on the Su-27, i do not know if it uses TVC to return to level flight but i can asure you it has good lateral control, because even the F-5 was flown without vertical tail and was found its forebody to keep the jet stable at yaw

I don't know what you mean by "vortex hysteresis" but let's be serious...do you seriously think the vortex lift specs of a SU-27 are better than a 15 years later developped plane???

Come on the F-22 flies 60° AOA at max Cl...(and no that is not because of TVC; TVC allows for more control at this AOA but the fact the plane flies there is because you have enough lift).

 

[rousseau]

You can't conclude anything from that; Mig 1.44 was meant to be in the same TOW than the supposed one of this plane (40 tons) and was meant to be maneuverable and agile.
Weight is not a problem as long as lift is here to compensate it;

Now the F-22 uses thrust vectoring, this improves roll rates, turn rates and AoA handling at high AoA.

Just correct one thing: TVC does not necessarily improve the roll rate despite its deflected differentially.

Actually (getting off topic a bit) the F-22's roll rate benefits significantly from TVC at higher AoA even though it is not deflected differentially. This is because, without TVC, the aerodynamic control surfaces must keep the noise pointed in the right direction during a roll; however, with TVC, the aerodynamic control surfaces can be devoted entirely to roll, with the TVC providing the needed pitch control.

(Chart source: Barham, Robert W. "Thrust Vector Aided Maneuvering of the YF-22 Advanced Tactical Fighter Prototype," N94-34610, March 1994.)

Oh my God! my great dear:
Please review the entire file all of YF-22. The YF-22 does IS a differential TVC aircraft

 

[rousseau]

TVC is not necessarily required. Before Su-37 #711 crashed, it was doing some interesting things. Sukhoi had refitted the aircraft with non-TVC AL-31F engines and had modified the flight control software. The result was that they were able to emulate the Su-37's TVC-aided maneuverability using non-TVC engines.

i agree but the reason TVC is used is to free some aerodynamic surfaces like tailplanes on the F-22, reduce their size like the T-50`s small vertical dorsal stabilizer and omit others like the canards on the Su-35BM, TVC becomes really handy for stealth aircraft for that reason.
I do not think the J-20 will do okay without it.

TO PAK FA:
IF YOU WILL BE BACK YOU HAVE TO ADMIT IT IS NOT EVERYONE WHO DEBATED WITH YOU HAD ALREADY OVERWHELMED YOU, JUST YOUR KNOWLEDGE IS NOT SUFFICIENT

Let's presume an aircraft with unlimited wing and even with no weight and no fuselage. let's say a infinite flying-wing like B-2 but no weight.
Does it flyable? you can say yes, but I can insist to no. You guys can not persuade me because you lose another condition. The condition here is air flow.
Let's push it faster, What PAK FA want to say is the unlimited weight will cause thrust to be very insufficient even can't make enough air flow to fly although the lift will compensate the weight.
To think it deeply where the lift come from? Only a wing applied with lift principle? What if I throw it into universe? It will fly via inertia not lift, that will make the topic irrelevant.

 

[rousseau]

If you want to be fair and true to your logic, then i point at the X-31 with only canards+ailerons and later only a miniaturized rudder that was able to pull maneuver the SU-37 never did and will never do.

What's kind of maneuver that Su-37 were not done but done by X-31?

Similarly if you want to speak about AOA performance, the YAK-130 without TVC and only conventional layout can maintain 41° of AOA while the SU-35 was rated at 35°.

Interesting, source?
Or you mean Su-35BM?

 

[rousseau]

I lost patience to read whole pieces, just remember, yes even concrete can fly if the speed of air-stream is fast enough, but here we are talking about agility and maneuverability. Under what we are debating, we have to say:
With same thrust, if wing area is fixed, then reducing weight is the key to make an aircraft more agile.
With same thrust, if weight has to be increased, then we need wing area enlarged to compensate.
Relate to J-20, I think what PAKFA want to say is sth below:
With thrust assumed WS-10 or WS-15 or whatever, the wing area can be measured roughly, then comparatively, it is possibly too weight to be agile due to its thrust impossible to reach F-119 or AL-41, and wing load is not enough to compensate its T/W.R.

 

[Ogami musashi]

What's kind of maneuver that Su-37 were not done but done by X-31?

This:

http://www.youtube.com/watch?v=GhonVYFIiP0&feature=related


And i don't even speak of the rates at which the planes did all those maneuvers.

Interesting, source?
Or you mean Su-35BM?

YAK-130 max AOA:
http://www.globalsecurity.org/military/world/russia/yak-130.htm (no this is not the only source for that, i have magazines when it flew its high AOA maneuvers)


For SU-35 i got it from ...russian knights when i was in macs 2003.

 

[Deino]

Is this real ... couldn't check at GE, since my internet at home has a complete break-down !

Surely in 2008 there was no J-20 ... but the picture itself looks real

http://img.fyjs.cn/Mon_1101/27_143222_d98755c57330e15.jpg

???? Any my internet is still down at home.

Here's the original link for the picture:

http://www.flickr.com/photos/digitalglobe-imagery/5347525358/sizes/o/in/photostream/

Deino

 

[Stargazer]

To PAK FA:
This bird is weird ;D

Its wierd but up to a certain degree i like it

Yeah me too. And although the PAK-FA is still the best looking new fighter around, the J-20 still looks 10 times better than the X-35!

 

[saintkatanalegacy]

Or you mean Su-35BM?

Su-35S

 

[sferrin]

To PAK FA:
This bird is weird ;D

Its wierd but up to a certain degree i like it

Yeah me too. And although the PAK-FA is still the best looking new fighter around, the J-20 still looks 10 times better than the X-35!

The J-20 looks more refined. PAK-FA seems like a kludge. As for the X-35, we could have been stuck with the X-32.

 

[N22YF]

You can't conclude anything from that; Mig 1.44 was meant to be in the same TOW than the supposed one of this plane (40 tons) and was meant to be maneuverable and agile.
Weight is not a problem as long as lift is here to compensate it;

Now the F-22 uses thrust vectoring, this improves roll rates, turn rates and AoA handling at high AoA.

Just correct one thing: TVC does not necessarily improve the roll rate despite its deflected differentially.

Actually (getting off topic a bit) the F-22's roll rate benefits significantly from TVC at higher AoA even though it is not deflected differentially. This is because, without TVC, the aerodynamic control surfaces must keep the noise pointed in the right direction during a roll; however, with TVC, the aerodynamic control surfaces can be devoted entirely to roll, with the TVC providing the needed pitch control.

(Chart source: Barham, Robert W. "Thrust Vector Aided Maneuvering of the YF-22 Advanced Tactical Fighter Prototype," N94-34610, March 1994.)

Oh my God! my great dear:
Please review the entire file all of YF-22. The YF-22 does IS a differential TVC aircraft

"Thrust vectoring as used on the YF-22 and F-22 provides the ability to attain and trim at very high angles of attack and increased pitch rates both in low speed and in supersonic flight. Furthermore, although the nozzles do not vector differentially, the use of vectoring increases the roll response and maximum roll rate attainable at high angles of attack. This is because the horizontal tail surfaces (stabilators) perform double duty, providing both pitch and (in conjunction with the ailerons and flaperons) roll control. The use of thrust vectoring for additional pitch control leaves more of the stabilator motion available for roll." - Advanced Tactical Fighter to F-22 Raptor:
Origins of the 21st Century Air Dominance Fighter, David C. Aronstein, Michael J. Hirschberg, Albert C. Piccirillo

 

[TinWing]

The most important question is whether we're looking at a technology demonstrator or something that approaches a pre-production prototype? Was this truly the "first flight?"

As far as the timing, it's perfectly likely that this public debut was meant to appeal to domestic decision makers, not a single foreign dignitary. I'm sure that the defense procurement process is just as convoluted in China as in any other country, and with the upcoming change in leadership, the J-20 might be at a critical juncture in program funding. Of course, who knows? Actually, Hu claimed he didn't know anything about it before hand? What does that indicate? Does that indicate autonomy on the part of the military or that civilian leaders simply don't feel the need to micromanage defense programs?

The only thing I can state with absolute certainty is that a nice paint job certainly makes a better first impression than patches of yellow primer.

 

[Abraham Gubler]

The most important question is whether we're looking at a technology demonstrator or something that approaches a pre-production prototype? Was this truly the "first flight?"

The celebration banner after the first flight has a very interesting name in it. This forum can't accept Chinese characters but the three characters before the number "01" translate to "confirmation machine" (literal) or "demonstrator" (meaning). PS "Prototype" is written with two very different characters.

 

[overscan (PaulMM)]

That is correct Abe, but the J-10 prototype was described in the same words.

 

[Abraham Gubler]

That is correct Abe, but the J-10 prototype was described in the same words.

Terminology.... The bane of everyone's exsistence...

 

[SOC]

Here's the original link for the picture:

http://www.flickr.com/photos/digitalglobe-imagery/5347525358/sizes/o/in/photostream/

Deino

The image was taken from the Digital Globe site and imported into Google Eart has an overlay. As the "native" imagery of Chengdu is from 2008 (at least the part showing the CAC facility is), 2008 shows up on-screen as the date of imagery. It was in fact captured in January of 2011, and is obviously real!

 

[Deino]

... It was in fact captured in January of 2011, and is obviously real!

Thanks a lot ...

Besides, here's a new picture showing the "panel-lines" of the weapons bays a bit better ...

Deino

 

[saintkatanalegacy]

better image analysis

 

[Abraham Gubler]

These bay door pictures appear to support my earlier analysis that the bays will not be very deep. Because of the need to displace the ducts for the intakes and also the likely central spine structure to support the nose. However like the F-22 the lack of depth of bays would still allow a large number of A2A missiles to be carried because the bays are so wide.

 

[JFC Fuller]

better image analysis

Outstanding, that is exactly what I saw in some pictures posted a while back...to my mind this suggests that this airframe is more prototype than technology demonstrator.

 

[rousseau]

You can't conclude anything from that; Mig 1.44 was meant to be in the same TOW than the supposed one of this plane (40 tons) and was meant to be maneuverable and agile.
Weight is not a problem as long as lift is here to compensate it;

Now the F-22 uses thrust vectoring, this improves roll rates, turn rates and AoA handling at high AoA.

Just correct one thing: TVC does not necessarily improve the roll rate despite its deflected differentially.

Actually (getting off topic a bit) the F-22's roll rate benefits significantly from TVC at higher AoA even though it is not deflected differentially. This is because, without TVC, the aerodynamic control surfaces must keep the noise pointed in the right direction during a roll; however, with TVC, the aerodynamic control surfaces can be devoted entirely to roll, with the TVC providing the needed pitch control.
(Chart source: Barham, Robert W. "Thrust Vector Aided Maneuvering of the YF-22 Advanced Tactical Fighter Prototype," N94-34610, March 1994.)

Oh my God! my great dear:
Please review the entire file all of YF-22. The YF-22 does IS a differential TVC aircraft

"Thrust vectoring as used on the YF-22 and F-22 provides the ability to attain and trim at very high angles of attack and increased pitch rates both in low speed and in supersonic flight. Furthermore, although the nozzles do not vector differentially, the use of vectoring increases the roll response and maximum roll rate attainable at high angles of attack. This is because the horizontal tail surfaces (stabilators) perform double duty, providing both pitch and (in conjunction with the ailerons and flaperons) roll control. The use of thrust vectoring for additional pitch control leaves more of the stabilator motion available for roll." - Advanced Tactical Fighter to F-22 Raptor:
Origins of the 21st Century Air Dominance Fighter, David C. Aronstein, Michael J. Hirschberg, Albert C. Piccirillo

Ok you win.
The doc N94-34610 I got much earlier than this thread in which "position the nozzle flaps to the proper angle and independent of the other engine" had been conceived as deflected differentially by me till you gave another source in which expressed "not differentially" clearly therefor, I have to reexamine the entire process.

According to the figure you given to:

We see clearly, the YF-22 win almost double times of roll rate under VTC on condition when it is during AoA no less than 20 degrees.
Hereby, your theory of the aircraft rolling faster in the freedom of movable air-surface given by VTC is right.
However, your theory will be limited in High AoA which defined by same Doc. at 20 degrees, as we can see along with the AoA trends down to level, the superior effectiveness of VTC on is significantly squeezed. It is no way to image that how to space out the gap of difference between VTC on and off in addition to recovering the AoA, despite we have differential VTC.
Meanwhile, the same book you quoted from also told us impressively that F-22 didn't match the roll rate goal. This is unexplainable except synchronized VTC.

 

[rousseau]

These bay door pictures appear to support my earlier analysis that the bays will not be very deep. Because of the need to displace the ducts for the intakes and also the likely central spine structure to support the nose. However like the F-22 the lack of depth of bays would still allow a large number of A2A missiles to be carried because the bays are so wide.

Well, I also notice that side weapon bay is much back from lip of inlet compare to the F-22. So there must be VG device there

 

[Sundog]

Well, I also notice that side weapon bay is much back from lip of inlet compare to the F-22. So there must be VG device there

I've yet to see any evidence of a VG device or a need for one. The bay is that far back to avoid the nose gear and the inlets are that far forward to support the canards and sidebays IMHO. The reason you need some distance back from the inlet leading edge is due to the fact that the inlet will smoothly curve to the middle of the fuselage, not immediately at the intake lip curve in to the middle. You need some distance to attain that and maintain clean airflow.

 

[saintkatanalegacy]

yep, there won't be room for VG actuators

as sundog mentioned, the bay has to be placed backward to allow the duct to smoothly curve in order to reduce bleeding from the intake offset and have better pressure recovery

 

[Sundog]

China got it's stealth tech from a Russian aircraft?

This story doesn't make any sense to me, unless they're refering to a previously undisclosed Russian aircraft.

 

[saintkatanalegacy]

reanalyzed

redone the lower right picture and reveals that the main bay is longer

bay doors have regular intervals of hinges at the side

the front edge of the main doors seem to be intentionally blurred(?) whereas other details are distinguishable. the jpeg compression blocks that are aligned with the bay door edge is an indication of intentional blurring(?)

 

[dannydale]

I love how Andy Warhol that last one came out! Fabulous!

 

[Deino]

Quite an interesting statement from Maya at SDF: He "confirms" again that THE prototype is only powered by AL-31F/FN ... no more info !

Deino ???

 

[flateric]

Another interesting thing that there were no new photos for more than week or so. Seems that someone decided that it's enough for now.

 

[Deino]

Another interesting thing that there were no new photos for more than week or so. Seems that someone decided that it's enough for now.

Agreed that's really strange ! ... just in comparison, when had the T-50 its second flight ??

Regarding the engine issue ... also what makes me suspicious is the different inner structure of this new engine, which is IMO different to a WS-10A.


Besides that, maybe some of You might be interested:
http://www.secretprojects.co.uk/forum/index.php/topic,1641.msg113989.html#msg113989

CHeers, Deino

 

[erkokite]

China got it's stealth tech from a Russian aircraft?

This story doesn't make any sense to me, unless they're refering to a previously undisclosed Russian aircraft.

Probably has his facts all wrong, like many people in congress.

 

[rousseau]

What's kind of maneuver that Su-37 were not done but done by X-31?

This:
http://www.youtube.com/watch?v=GhonVYFIiP
And i don't even speak of the rates at which the planes did all those maneuvers.

[flash=200,200]http://www.youtube.com/watch?v=X8vIESTZPQo[/flash]
See the 02:12~02:26,same maneuver with different angle of view.

 

[rousseau]

Quite an interesting statement from Maya at SDF: He "confirms" again that THE prototype is only powered by AL-31F/FN ... no more info !

Deino ???

Deino:
Let's do it logically.
First step, get the weight. you might not have the official data of the weight, but conjecturing its size is not so much difficult now.
A fighter with 22 meters length, almost 15 meters wing span, it will be no less than 19 tons for sure in terms of its layout seeming.
Second step, collect all of presented data of engine.
We all know thrust of AF-31 series engine won't beyond than 13 tons each, the WS-10 according to information from China merely is modification version of AL-31 combined with some F110 tech maybe, so its thrust will approach to 13 tons more or less.
Such power is distinctly insufficient, no matter this aircraft will be testbed or prototype.
So conclusion is this engine with seemingly different nozzle from AL-31 must be WS-10Kai

 

[Ogami musashi]

What's kind of maneuver that Su-37 were not done but done by X-31?

This:
http://www.youtube.com/watch?v=GhonVYFIiP
And i don't even speak of the rates at which the planes did all those maneuvers.

[flash=200,200]http://www.youtube.com/watch?v=X8vIESTZPQo[/flash]
See the 02:12~02:26,same maneuver with different angle of view.

I see two completely different maneuvers..