J-20... The New Generation Fighter II

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bluewater2012

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Re: J-20... The New Generation Fighter

Here are a few things puzzling me. I watched the takeoff video over and over again. I noticed following facts:
1. It takes less than 15 sec to take off. (speed 0 to wheel leave the ground)

If you paid careful attention to the video (assuming same source), you'll notice there's a slight cut during J-20 preparing to take off unlike J-10B flight (unaltered), so I doubt anyone could say how long it took for it to take off beside the people that were at the site.
 

Quickie

Colonel
Re: J-20... The New Generation Fighter

Hi Everyone,

I am new here. I join this forum because there are many good professional analysis here.
Here are a few things puzzling me. I watched the takeoff video over and over again. I noticed following facts:
1. It takes less than 15 sec to take off. (speed 0 to wheel leave the ground)
2. The takeoff speed seems low.
3. The takeoff distance seems quite short. Some Chinese claims that it's only about 200m. I don't believe that. Let me take 300m for the time being.

4. There is absolutely no flame been seen at the nozzle. Not even a little redness.

Let's discuss 1-3 first.
I pull out my calculator, if I take 300m as the takeoff distance, I got 144km/h take off speed. There is no way for that beast to take off at this speed!
So I assume the take off speed was 230km/h, I got 480m of takeoff distance, which seems much longer than what we saw.
The truth may be between, but no matter how you slice it, the takeoff is damn impressive!
Anyone figure out or knows the real takeoff speed and distance?

Let discuss point 4.
When I first saw the picture of J-20, I thought the designer simply give up on the IR stealth. Now I am not sure. Any comments?

I think the acceleration increases from the start of takeoff, right to when the load starts to lighten on the wheels, right through the lifting of front wheel. i.e. Engine thrust will not stay the same but will start to increase as well, and at the same time the resistance from the wheels lessen when the load on it starts to lighten. So, the takeoff speed should be higher than in your maths. Using constant acceleration, I actually got the same speed 144km/hr.

On the IR emmision, someone in another forum pointed out that the silvery nozzle is actually a bad emitter of IR.
 
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Blitzo

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I got a few questions abou the airframe of the J-20:

1) how many hardpints could J-20 have? from a few photos showing he bottom of the plane, it seems that J-20's internal weapons bay is not too big (the area between the landing gears)...

2) from comparing J-20 with F-22, J-20 has the canards as well as movable tails while F-22 has no canard and fixed tails. It seems that J-20 is the only plane out of the 3 stealth fighters with canards and with the smallest wings. So how would all these affect manueverability either positively or negatively?

3) I seem to remember seeing photos of J-20 with a tint of green in its cockpit. So what is that? Is that the holographic (spelling?) HUD?

4) the landing gears seem to be much bulkier than other heavy fighters like Su-27, especially looking from the front. Is this because the stealth plane is much heavier than convetional fighters?

5) Someone asked earlier about the possibility of only changing the nozzle of the engine instead of changing the whole engine. And no one has commented on that yet. So is it possible for them to haul the plane to a place change the nozzle of the plane? So there is actually only one plane with the same engine, only different nozzle? I personally don't think this idea is a little far fetched, but I don't know.

Thanks

1: It could have the same number as the F-22, in the same exact layout. The main weapon bays could be longer than the F-22s though. The prototype doesn't seem to have weapon bays for some reason -- either that or the engineers made it so flush it's impossible to discern at this resolution. But imho the weapon bays on the 2001 prototype at least, is nonexistant and there's probably an empty space/mass equivalent there instead.
3: Yeah the glow from the HUD from modern fighters usually means it's holographic. Not sure why it glows like that, but apparently they do :/
It looks waaaay cool.
4: Tbh I think the landing gear doesn't look that bulky and is similar to the F-22. the T-50's landing gear looks far bulkier and looks almost destined for carrier duty.

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according to russian magazine, the frontal RCS for J-20 is 0.05m or 5mm

Well we all know how accurate the russians are.
 
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Quickie

Colonel
If you are talking about the first two photos, the angles of the tails in those photos are different. The tail in the first photos is more straight while the tail in the second pic is tilted. So the difference in distance between the line and star may be an optical illusion.

The angle of view will not matter if all your references is in the same picture, which is what I have suggested to use when comparing the distances. In one picture, the distance between the nearest point of the star and the line is actually shorter when compared to the distance between the line and the front edge of the rudder. This is the other way round for the other picture with the different nozzle.
 

Blitzo

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No you are getting two different aspects mixed up. In my last post to Martin I was referring to the bottom section in a article posted by Kyli POst 465 and reproduced at the bottom of this post. THe bolden part is what Im suggesting martin is dismissing out of hand.

The one you are talking about was just an unsubstantiated opinion I cut and pasted from the WAB forum to illustrate another POV found on a pro western forum.

Re: J-20... The New Generation Fighter II
Anti-Stealth Sensors to Tackle Chinese and Russian LO Designs


Anti-Stealth Sensors to Tackle Chinese and Russian LO Designs
Posted by David A. Fulghum at 1/11/2011 2:13 PM CST
With first flight out of the way, the discussion about China’s new J-20 stealth prototype is switching to the aircraft’s mission (fighter or, more likely, long-range strike), sensors (strike missions would require a high-resolution long-range radar) and communications (which would demand high-speed datalinks and sophisticated integration).

Conventional radars have only one-half to one-third of the range of an active, electronically scanned array (AESA) radar. Moreover, the movement of a conventional, mechanically-scanned radar antenna provides a tell-tale glint of radio frequency (RF) reflections to enemy aircraft with advanced radars. Such reflections slash at the effectiveness of a stealth airframe. China is known to be pursuing newer radar technology.

“It's too early to tell the true status of the Chinese AESA program,” says a Washington-based intelligence official. “We've seen lots of press and airshow info on the program, but that doesn't automatically translate into a robust development or give us an accurate look at where the PRC is as far as fielding one anytime soon.

“Like the [high-performance] engine, it'll be a challenge to take the step from older radars to one designed for a 5th-Gen fighter,” he says. “Again, though, the J-20 is just the first or second -- depending on whom you believe -- prototype into a very long development program.”

A two-seat J-10 fighter acted as chase plane for the J-20 during the flight

Photographs show the J-20 flying at shallow angles of attack and with its undercarriage extended. An observer posting minute-by-minute reports of proceedings to the Global Times, apparently from the fence at Avic’s Chengdu facility, said at 12:50:08 local time (04:50:08 GMT) that the aircraft had begun moving, following a second later with “accelerating” and at 12:50:16 “flying”. The landing was reported 18 minutes later.

Two passenger aircraft, one a 737, arrived at the Chengdu facility less than an hour before the J-20’s takeoff, presumably carrying important officials. The Chengdu plant is part of the Avic combat aircraft division, Avic Defense.

“Chinese military [sources] are saying that the first test pilot for the new Chinese fighter is Liang Wanjun,” the analyst says. “He has previously test flown the J-7, J-10 and JF-17. Liang has a total of 2,300 flying hours, joined the PLAAF in 1982 and became a test pilot in 1998.

It is unclear whether the J-20 is a prototype or only a technology demonstrator. Either way, it is not the only program for an advanced combat aircraft.

The deputy chief of the air force, He Weirong, said in November 2009 that in 2017-19 China would field a “fourth-generation” fighter, which in China means an aircraft of the F-22’s technology level. He was not referring to the J-20, however, because a month later a prominent news report in English quoted the People’s Liberation Army Air Force (PLAAF) as saying that the 2017-19 fighter would be an improved J-10. It is possible that the 2017-19 fighter is a supercruise version of the J-10 since the Chinese navy has expressed the need for an aircraft that can maintain fuel-efficient, long-distance, supersonic flight, a necessity for keeping enemy forces away from the coast of China.

The Chengdu J-20 design has struck most analysts and observers as familiar and somewhat different that the Lockheed-Martin F-22 and F-35 as well as the Sukhoi T-50.

“The J-20 is reminiscent of the Russian MiG 1.42 both in terms of planform, and also with regard to the rear fuselage configuration,” says Douglas Barrie, senior fellow for military aerospace at London’s International Institute for Strategic Studies. “The most obvious difference is the greater forward fuselage shaping as the basis for low observable characteristics, along with the different engine intake configuration. The MiG program was cancelled by the Russian government around 1997.”

Others note that the planform also has a resemblance to Sweden’s SAAB Viggen.

Another issue that will continue to surround all stealth designs is how long will current stealth designs offer invulnerability as air defenses adopt even larger and more powerful AESA radars. From the early days of AESA development, a key goal was to build a radar that can detect a very small object like a cruise missile at a distance great enough to target and shoot it down or a larger object like a fighter with a very low observable treatment.

Airborne detection of stealth aircraft may have already been accomplished in a series of tests done at Edwards AFB, Calif. in the second half of 2009. Those with insight into the research say Lockheed Martin’s CATbird avionics testbed –a 737 that carries the F-35 joint strike fighter’s entire avionics system -- engaged a mixed force of F-22s and F-15s and was able to target the F-22s.

"The F-35 mission systems suite is the most sophisticated and powerful avionics package of any fighter in the world," said Dan Crowley, Lockheed Martin executive vice president and F-35 program general manager at the time of the tests.

His clue about the fighter’s anti-stealth capability is in a reference to confronting new, sophisticated, foreign aircraft.

“The F-35's avionics include on-board sensors that will enable pilots to strike fixed or moving ground targets in high-threat environments, day or night, in any weather, while simultaneously targeting and eliminating advanced airborne threats,” Crowley said.


The sensors on the F-35 which they imply to be anti stealth I believe are really just electro optic sensors like DAS and the IRST.

Most of this article is bull (you can tell with the thinly veiled comparison to the Viggen. Man they're gettin desperate...) -- and they miss out that the Russians and the chinese have been doing anti stealth for a long while, probably longer than the Americans.
 

Blitzo

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IMO how successful your stealth plane is, dependent on the complete package. If the other guy has a superior weapons suite and radar etc etc , which allows him to see you before you see him then youre toast. Nothing can be more demoralising then seeing your fellow pilots being downed, and you don't know where its coming from.

as a example heres what one guy over at WAB opinionated?. Note Im not saying he's correct, because i haven't a clue on judging whether he's on solid ground when it comes to crunching the numbers.

"..... So, the J-20 should have a 50% larger AESA than the F-22, which, if the Chinese can get their AESA technology right, should increase SnR in DB by 50%, or reduce the F-22's effective RCS by 1.8 DB. If it's in the F-35 RCS range, then that reduces the DBSM difference from 10 to 8.2, which reduces the F-22's detection range advantage to 170/70%; the F-22 can spot the J-20 at 170% the distance the J-20 would. So, this works out to something around the J-20 getting detected at 22 nm and the F-22 getting spotted at 13 nm. The J-20 would get detected by the F-35 at 16.5 nm and detect the F-35 at 19 nm..........."

Wow isn't it a bit early to start giving out real numbers? Espicially if we don't know what kind of RCS J-20 has in the first place.

I'm sure the PLAAF already have tactics for use against F-22s in place, even if it's just to survive the initial wave of BVRAAMs. It will be interesting to see the J-20 vs J-10s and J-11s.
 

delft

Brigadier
Your reasoning would be correct, if the tail planes were flat planes, but they aren't. A better point seems to me a light colored patch near the cockpit. One 'plane has it, the other not, I think. You can check that the photograph has not been mirrored by looking at the 2001.
 

Quickie

Colonel
Your reasoning would be correct, if the tail planes were flat planes, but they aren't. A better point seems to me a light colored patch near the cockpit. One 'plane has it, the other not, I think. You can check that the photograph has not been mirrored by looking at the 2001.

A quick one as I've got to go now.

It doesn't matter they are flat or curved. The 2 rudders are dimensionally identical copy, meaning the curves, where ever it is, will be the same. As to the angle of the shot, it'll matter only if it's a close distance shot. We'll have to see more pictures to see if it's really a photographic effect.
 
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delft

Brigadier
I mean that the forward line of the tail planes as seen on the photographs are not the leading edges. I still think you're probably right.
 
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