J-20... The New Generation Fighter III

paintgun said:

i thought that was a typical HK love song, until i see the big red caption lol, and hear the ref part

this 27-2 flight is amazing, it's an all out burn and turn, and like AF brat say they be better be extra careful with the bird
i don't know enough to analyze the turn performance and else, but to me this bird finally do turn like an agile fighter, and anyone one else who says otherwise (J-20 is a striker school) better be thinking hard on their opinion

edit : another 27-2 video

[video=youtube;RxfncfOCvPk]http://www.youtube.com/watch?feature=player_embedded&v=RxfncfOCvPk[/video]

AFbrat, is that an immelmann? you spotted it a page ago, good vid as well, provides another angle, also showing the Chengdu wallclimber crew, with freaking accent

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The turn from 1:33 to 1:24 is half a circle. 9 seconds in half a circle which gives an approximation of 18 seconds in a full circle. If I'm not mistaken this is comparable to J-10.

Quickie said:

The turn from 1:33 to 1:24 is half a circle. 9 seconds in half a circle which gives an approximation of 18 seconds in a full circle. If I'm not mistaken this is comparable to J-10.

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You mean it's comparable to the production J-10, right?

If so, that would be very good for a prototype still running initial test flights and definitely not running on WS-15 yet, I guess?

P.S. The "I guess" part refers to the whole sentence, not the WS-15 part.

Player99 said:

You it's comparable to the production J-10, right? If so, that would be very good for a prototype still running initial test flights, I guess?

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360 in 18 seconds is only a sustained turn rate of 20 degrees/s. That is not bad when you consider that the F15/F16 has sustained turn rates of 15-16 degree/s while the MKI has a sustained turn rate of 22-23 degree/s, which is similar to that of the Rafale (24 degree/s) and Typhoon (23 degree/s). But according to some sources, the F22 has a sustained turn rate close to 30 degree/s (while others put it at 23/24 degree/s).

Now, I would be very disappointed if the J10 does not have a sustained turn rate better than 20 degree/s. Considering that the J10 is supposed to dominate flankers in wvr, and since the Su27 has a sustained turn rate of 21 degree/s, I think it would be safe to infer that the J10 has a better sustained turn rate than that.

I would say that given how early we still are in the J20 test programme, the fact that the J20 prototype is flying with engine that are significantly weaker than their intended in-service ones, and the likely sustained turn rate the J10 can achieve, I think it would not be unreasonable to expect the J20 to be able to have a significantly better sustained turn rate than the implied 20 degree/s as this latest vid shows.

plawolf said:

360 in 18 seconds is only a sustained turn rate of 20 degrees/s. That is not bad when you consider that the F15/F16 has sustained turn rates of 15-16 degree/s while the MKI has a sustained turn rate of 22-23 degree/s, which is similar to that of the Rafale (24 degree/s) and Typhoon (23 degree/s). But according to some sources, the F22 has a sustained turn rate close to 30 degree/s (while others put it at 23/24 degree/s).

Now, I would be very disappointed if the J10 does not have a sustained turn rate better than 20 degree/s. Considering that the J10 is supposed to dominate flankers in wvr, and since the Su27 has a sustained turn rate of 21 degree/s, I think it would be safe to infer that the J10 has a better sustained turn rate than that.

I would say that given how early we still are in the J20 test programme, the fact that the J20 prototype is flying with engine that are significantly weaker than their intended in-service ones, and the likely sustained turn rate the J10 can achieve, I think it would not be unreasonable to expect the J20 to be able to have a significantly better sustained turn rate than the implied 20 degree/s as this latest vid shows.

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I'm not sure on the 18 seconds figure for J-10 neither. Got it from hearsay.

Sustained turn rate, though, doesn't that vary with altitude and velocity?

Let's assume what we're seeing is due to engine issues. 155kn divided by 122.5kn is ~1.25, multiplied by the probable weight of the weapons on full combat load, you get about 1.20 increase in T/W on a production model.

If someone can help me with the aerodynamic equations, I'd be grateful, but just going through a naive model which assumes that sustained turn rate, all other factors being equal, is linear with thrust/weight, you'd get something like a 24 degrees / second on a production model using a 155kn engine. That's fairly respectable, although not at the level of a F-22 with TVC, which is supposedly around 28 degrees per second, and would be highly outclassed by the PAK-FA which was designed to outperform the F-22 when it comes to maneuverability. TVC is supposed to add between 10 and 20% additional turn rate, so that would come out to 26.4 or 28.8 degrees with TVC + 155kn engines. Up to par with the F-22, although still outclassed by the PAK-FA.

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Just remember, though. The J-20 is more optimized for speed and range. The key criteria of the J-20, compared to the F-22 and PAK-FA, is high speed super-cruise and long range. This has to be achievable even if the WS-15 program hits a snag and the final engines are only WS-10Gs or even WS-10Bs. For these reasons, the J-20 has put less emphasis on maneuverability; it only needs to meet the F-22, not exceed it. If it has to fight the PAK-FA, it will attempt to win in BVR, and if it cannot, it'll just flee from the battlefield.

In any case, this indicates a minimum maximum sustained turn rate. For all we know, the plane isn't being flown at its maximum capabilities; it could be flying at 100% fuel, or the pilot could just be taking it easy given the fact that the plane is being video-taped by onlookers. We can say it at least would meet the F-22 with better engines and TVC.

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Regarding the J-10; being superior in WVR is more to do with instantaneous turn rate. The J-10 can very well have a turn rate of 20 degrees per second, which is appreciably inferior to the Rafale, yet still outperform the Su-27 in WVR due to a higher instantaneous turn rate.

Player99 said:

Yeah, 100 some meters would be to scary to think about. I'm clueless, but 2000 meters appears too much. Could you find a way and do a more precise estimate?

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My semi educated guess gentlemen is a floor of 500 meters or so, with a max of maybe 1500 meters as he pulls to the vertical. It has probably been 15 years maybe 20 since I knew such things, but I know someone will gladly correct me if I'm remiss, I believe that in the US the minimum altitude for an aerobatic demonstration is 500ft, for someone who is superhumanly proficient and a more normal floor of 1500ft. I believe he is around 500 meters when he is doing his low level turn and burn, at least two factors are limiting, he is over a populated area, and his visibilty appears to be maybe 5 miles at best and I would guess the ceiling is around 1500 meters. I would doubt that he is doing a max effort turn, but he is probably having to grunt a little. It looks like he is doing an immellman turn, named after max immellman, a german fighter pilot, in WW1 I believe, It is basically the first half of a loop, with a roll on top, it accomplishes two things, it points you 180 in the opposite direction and gives you altitude, which are both at a premium. In the old days the roll on top needed to be smooth and precise otherwise you could dish out and end up lossing lots of altitude if you departed the aircraft, and lost control, then the guy on top put the nose down and closed in for the kill. The opposite manuever is the split S, where you basically rolled the aircraft and pulled, if you were low it was basically a desparation manuever, and lots of fellows flew into the ground, if you were hi, it could work, although in a Mustang, 109, FW=190 and you stayed in the power, you could mach out pretty quick, and while nobody ever went supersonic, lots of guys got flutter from control surfaces etc. Now having blathered on, I love it when you guys start to get in to the flying end of things, and talking about A2A, which is what the J-20 is all about. Maybe the tallman could come on Air Combat with Max and they could do a little tactical discussion an discuss one anothers airplane. The PLAAF is obviously proud of their bird, I believe it has surprised a lot of people and if they get it in production in numbers even some of the dummies who killed the Raptor will be wringing their hands. I am frankly somewhat less hopefull for our other baby bird but who knows, lets watch the comparisons, we want to have a respectfull discussion of true capabilities and avoid the comparo. I really see no reason why the tall man couldn't come on and tell us a little about his airplane, no top secret stuff, just hanger flying a little. Carry on gentlemen, and good work, its good to see you guys tuned in on some aviation stuff. I really do hope we can find a few throttle jockeys to give us some honest commentary, as I know how limited my own knowledge is, I love to learn about all these fine airplanes and their pilots and mechanics.

The latest rumors indicate that there are far superior videos of the 27th flight still being withheld in private forums. We have to wait a couple more days and if we are lucky some one would sneak them out.

Inst said:

Sustained turn rate, though, doesn't that vary with altitude and velocity?

Let's assume what we're seeing is due to engine issues. 155kn divided by 122.5kn is ~1.25, multiplied by the probable weight of the weapons on full combat load, you get about 1.20 increase in T/W on a production model.

If someone can help me with the aerodynamic equations, I'd be grateful, but just going through a naive model which assumes that sustained turn rate, all other factors being equal, is linear with thrust/weight, you'd get something like a 24 degrees / second on a production model using a 155kn engine. That's fairly respectable, although not at the level of a F-22 with TVC, which is supposedly around 28 degrees per second, and would be highly outclassed by the PAK-FA which was designed to outperform the F-22 when it comes to maneuverability. TVC is supposed to add between 10 and 20% additional turn rate, so that would come out to 26.4 or 28.8 degrees with TVC + 155kn engines. Up to par with the F-22, although still outclassed by the PAK-FA.

===

Just remember, though. The J-20 is more optimized for speed and range. The key criteria of the J-20, compared to the F-22 and PAK-FA, is high speed super-cruise and long range. This has to be achievable even if the WS-15 program hits a snag and the final engines are only WS-10Gs or even WS-10Bs. For these reasons, the J-20 has put less emphasis on maneuverability; it only needs to meet the F-22, not exceed it. If it has to fight the PAK-FA, it will attempt to win in BVR, and if it cannot, it'll just flee from the battlefield.

In any case, this indicates a minimum maximum sustained turn rate. For all we know, the plane isn't being flown at its maximum capabilities; it could be flying at 100% fuel, or the pilot could just be taking it easy given the fact that the plane is being video-taped by onlookers. We can say it at least would meet the F-22 with better engines and TVC.

===

Regarding the J-10; being superior in WVR is more to do with instantaneous turn rate. The J-10 can very well have a turn rate of 20 degrees per second, which is appreciably inferior to the Rafale, yet still outperform the Su-27 in WVR due to a higher instantaneous turn rate.

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up to what i read, any fighter has an Ideal turn rate, i mean if you see most jets have an ideal turn rate with 50% fuel and weapons, many of the figures for turn rates quoted for fighters you see are at that configuration.

To give you an example it is said the F-20 could out turn an F-18 but only without external stores, once armed the F-18 was better, the answer is drag, higher drag means less lift.
The F-20 armed will generate more drag and by being singled engined reduce the thrust available to counter that induced drag, thus armed the F-18 is better and has higher turn rate

Instantaneous turn rate equals max lift at max AoA attainable, while sustained turn equal max steady turn rate where lift is balanced by drag and thrust, less drag higher sustained turn rate.

Fifth generation fighters have very good turn rates because they have no external weapons stores, thus they generate less drag
If you compare any fourth generation fighter with a fifth generation one, you will　find the fourth generation fighter without external stores has actually better aerodynamics than the fifth generation fighter because they usually do not have stealth compromises, but the fifth generation fighters by carrying no external stores actually turn better, also fifth generation fighters use TVC nozzles that increase turn rates thus they usually have better turn rates than fourth generation jets.



The Russians made a study and found F-22 by having a larger cross section actually generates more drag than Su-27, however the trick of the Russians was the Su-27 was empty without no external stores, add external stores and the Flanker is way much draggier.

If you see the numbers of Eurofighter and F-22 you find both jets also are very close in wing loading and thrust to weight ratio, in fact the Eurofighter has slightly better numbers, however the Eurofighter can only compete with F-22 empty, add weapons, and the Eurofighter has lower turn rate, thus at the end F-22 will out perform both Su-27 and Eurofighter.

Thats cool, its interesting to speculate, but as we see this aircraft gaining in capability, the videos are nice, and honestly if they were concerned about these videos, we wouldn't know a thing. This is a very attractive PR medium and I'm fairly certain, that all the right folks know about Sino D, and while many of us are just enthusiasts, we disseminate a lot of favorable rep for the black bird and the Chinese military as a whole. I sincerely hope that this bodes well for our future relations, like everything else it can go either way, but I do have a great deal of respect for the Chinese people and pray that with mutual respect and hopefully more trust on both sides it can be a mutually advantageous relationship for us all, right now I'm honestly more dissapointed with our own leadership, I'm certainly not willing to give up my own freedom and I promise I will fight for yours as well.

Air Force Brat said:

Thats cool, its interesting to speculate, but as we see this aircraft gaining in capability, the videos are nice, and honestly if they were concerned about these videos, we wouldn't know a thing. This is a very attractive PR medium and I'm fairly certain, that all the right folks know about Sino D, and while many of us are just enthusiasts, we disseminate a lot of favorable rep for the black bird and the Chinese military as a whole. I sincerely hope that this bodes well for our future relations, like everything else it can go either way, but I do have a great deal of respect for the Chinese people and pray that with mutual respect and hopefully more trust on both sides it can be a mutually advantageous relationship for us all, right now I'm honestly more dissapointed with our own leadership, I'm certainly not willing to give up my own freedom and I promise I will fight for yours as well.

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To add to that (and go off topic and rant for a bit) I would just comment on how amazing it is for sinodefence to bring people with different political, ethnic, and religious background and essentially let everyone interact in a constructive manner.