J-20... The New Generation Fighter III

Originally Posted by kyuryu

Could it be a mixed of both approaches ie the first J-20/A production batch/es being equipped with uprated WS-10s to ensure the stated 2017/18 timeline is meet to achieve IOC, with or without TVC, with subsequent, production switching to a J-20/B with WS-15 + TVC.

It still makes sense for a uprated WS-10 to be developed, especially one with a normal lifespan / TBO, to be incorporated into J-10B, J-15, J-16 and even an AESA equipped J-11C (SU-35 analogue), replacing the current J-11B production run.

While the J-20 is an awesome plane, production ready-aircraft won't be available for at least another 5-7 years, therefore it make sense to squeeze the maximize performance out of existing airframe designs through upgrades to radar, EW systems, introduction of composites and uprated engines to keep them competitive with Western 4++ Gen aircraft...

I can't imagine there will be another flanker derivative beyond J-15 and J-16, and the PLAAF don't exactly need an Su-35 "analogue". J-11B retrofitted with AESA and modern A2A weapons could give it a run in A2A and J-16 would have greater A2G capability. No need to put the two onto one airframe.

I can imagine there will be an upgraded WS-10 version in time, but I'm not sure if existing fighters will be necessarily re engined; do USAF F-16 and F-15s get re engined with new versions of their engines?

And the IOC date stated would be a fighter with the "4S" in that famous CCTV interview. I wonder if J-20 can supercruise and manouver competitively with uprated WS-10s, if the engine exists. Personally I'm still of the belief that the engine equipped aboard the next prototype will be WS-15, until something else comes along to direct otherwise.

Originally Posted by tphuang

The higher thrust WS-10 has been in development for many years. It's definitely further along than WS-15. You can put it on J-10B, J-15, J-16. There are plenty of platforms that can use it. And the first batch of J-20 might end up with upgraded J-10 if WS-15 is not ready.

Look up the engine thread and read what Maya wrote about WS-15. He is as good source as any on it regarding when this project is expected to be ready. I think putting WS-15 on J-20 in 2013 sounds really ahead of curve based on the stuff I've read before.

Well given the IOC date is 2017-2019, 2013 does seem a little early for WS-15 to be equipped aboard a prototype; 2015 will probably be the latest time where a WS-15 J-20 must show up to let the IOC date make sense, given it'll take about two years at least for the final prototype/preproduction planes to be tested.

Hmm the last update was a while ago though.

Someone on a Chinese forum posted papers on the subject of canard and RCS. The first paper discusses methods for reducing RCS on an aircraft with canard configuration.

《低RCS 飞行器外形设计实践》 航空学报 1995年


On the basis of the canard configuration a contour stealth design including chiefly the wing, the fuselage and their connection type is projected. The prime project of a blended wing body vehicle with canard is provided and through the change of the fuselage head form and the different fin disposals, the radar cross section (RCS) is optimized. The average value of RCS and the value of RCS in the ± 45 ° front sector for different designs are illustrated. The model measurement proves that the project having a sharp head fuselage and 30 ° angle double fin has the minimum value of RCS. The wind tunnel test to the model with RCS optimized proved that the vehicle project has excellent aerodynamic characteristics such as high lift curve slope, up to 26° stalling angle, high lift / drag ratio equal to 8, and also has low RCS value in the front sector and in the lateral sector.







A second paper discusses the result of an experiment conducted inside an anechoic chamber. Wooden models with tin foil coating were used in the experiment. Among the findings is that the canard configuration tested has lower RCS than the traditional configuration tested.

《带边条后掠翼融合体隐身布局的应用研究》 气动实验与测量控制 1995年


The third paper is more recent, which studied canard geometry and its effects on RCS. The first three images show the effect of sweep and span on RCS value. Forth and fifth images show deflection of canard and its influence on RCS. The last image shows the effect of applying RAM on the canard.

《鸭翼电磁散射特性分析与RCS减缩方法研究》 航空计算技术2010

Now, some information on aerodynamics. The first paper concluded canard configuration has advantages over traditional configuration. I don't have time to translate everything, so I will just summarize.

1. Canard can provide better pitch-down moment compared to tailplane. This is because tailplane needs positive deflection at high angle-of-attack to push the nose down, resulting in stall. Canard uses negative deflection to bring the nose down, thus doesn't stall.
2. Canard has reduced supersonic drag as compared to tailplane. The amount of shift of aerodynamic center is reduced on a canard configuration, resulting in easier time to trim the aircraft for the canard.
3. TVC performs better with canard, in that mass does not concentrated on the aft portion of the aircraft thus enhances trimming efficiency. Canard when combined with TVC can enhance lift, which is not achievable with traditional configuration.
4. This point reiterates that canard can provide better trimming than tailplane. Furthermore, differential canard enables the control of side slip, which is not achievable with traditional configuration.
5. Relax stability actually makes trimming more difficult for tailplane because of shorter moment arm. Canard doesn't have such problem. Furthermore, canard can work in conjunction with flaps, reducing the area needed for trimming.
6. Canard can be used with forward-swept wings. There is no example of aircraft that uses forward swept wing and tailplane at the same time.

《近距耦合鸭式布局气动研究进展》 空气动力学学报 2003





The second paper also compared canard configuration with traditional configuration. Among the finding is that canard configuration provides better yaw capability over traditional configuration at high angle-of-attack.

《带边条后掠翼融合体隐身布局的应用研究》 气动实验与测量控制 1995年

Originally Posted by Engineer

There is no example of aircraft that uses forward swept wing and tailplane at the same time.

Isn't the Su-47 a FSW with tailplanes? Do they mean something more specific?

Originally Posted by Engineer

[*]Canard can be used with forward-swept wings. There is no example of aircraft that uses forward swept wing and tailplane at the same time.

The X29 would disagree.

x29.jpg

The argument the study was making was in regard to the advantage of the use of canards as the pitch control surfaces. In this context, it has to be referring to the horizontal tail planes and not the vertical tailplanes. What we're seeing in the above 2 examples are vertical stabilizers.

Originally Posted by kwaigonegin

The X29 would disagree.

x29.jpg

Actually, the X-29 agrees as it uses canard and not tailplane.

Originally Posted by kyanges

Isn't the Su-47 a FSW with tailplanes? Do they mean something more specific?

The S-47 actually uses triplane configuration. So even though the aircraft has tailplane, the aircraft is not traditional configuration.

Originally Posted by Engineer

Actually, the X-29 agrees as it uses canard and not tailplane.

I think I know what you;re saying Engineer but you need to be clearer. When you say tailplane are you talking about the vertical stabilizers (rudder) or horizontal stabilizers (elevators)?
It seemed like you were talking about tailplane (vertical stabilizers) but was probably refering to elevators.

Originally Posted by Engineer

The S-47 actually uses triplane configuration. So even though the aircraft has tailplane, the aircraft is not traditional configuration.

Hi Eng, I think this discussion should be moved to the aerodynamics thread which was specifically created by seige in order that we might have these discussions without offending those who have no interest in the aerodynamic aspect of the J-20, while I love these discussions myself others who may not understand our concerns?

besides that I'm picking up a primary return of the fat pilot on my six! Has anyone confirmed that the latest aircraft photos are in fact 2003?

Of course the horizontal tail planes were ment. I suppose this concerns aircraft with supersonic capabilities. The first two aircraft with negative sweep, the Ju-287 experimental heavy jet bomber and the Hamburger Flugzeugbau HFB-320 Hansa Jet, had conventional horizontal tail planes.

2002 with a green radome and no pitot tube. PSed?

Originally Posted by AssassinsMace

2002 with a green radome and no pitot tube. PSed?

Hmmm ... IMO a FAKE !

Deino

This might be disappointing a bit.