Chengdu J-20 5th Generation Aircraft News & Discussions

[Xracer]

So SEXY man

 

[peaceful]

thx hk299792458 and 向老大哥致敬

希望早日装配国产发动机，完成全国产化。

 

[gambit]

How is it irrelevant Gambit? a plane's intended mission plays a crucial role in the design.
And that is why I mentioned the intended mission of the MiG-25 & A-5 & F-15. If one was a bomber and the other was an interceptor and the other a air-superiority figher, then how can they have striking similarities ?

It is irrelevant in the sense that its original mission was brought into the debate in trying to distinguish one aircraft's origin from another when the aircraft itself gained many more missions. I am not saying that the original missions made them physically similar. I am saying that their physical similarities hinted at the same original design, which in this case the A-5 is the oldest.

 

[houshanghai]

J20 AND J10B

 

[Zabaniyah]

Why you brought my CDF comment to PDF?

You are just a troll beyond pathetic.

 

[VelocuR]

Just curious, what kind of advanced engines on J20? reliables?

How come JF-17/J-10B don't have own engines apart from Russian engines??

 

[homing28]

2011-11-12

J20 video
j-20 11

 

[houshanghai]

J 20 - 2011 11 12 - J20 45th Test Flight in Chengdu

thx 汉魂雄风 shoot and thx himitechworld upload

 

[Bratva]

Just curious, what kind of advanced engines on J20? reliables?

How come JF-17/J-10B don't have own engines apart from Russian engines??

1. Advance engines are in making for J-20 with reduce IR signature as well as reduce harmonics generating from engine which is can be detected by radar too.

2. Engine reliability issues. Chinese have just mastered the engine technology so next is mass production which they lack right now kind of ,so in order to compensate all these, they use russian engines

 

[gambit]

A conversation about flight controls from elsewhere...

Actually I see only slight bobbing during the take off which could be due to a slight flipping of the elevon during that time. I remember seeing a video of the elevons and stabilizers flipping wildly during take off. The oscillation could also be due to the undulating surface of the runway somehow matching close to the oscillaton frequency of the undercarriage.

Wrong.

It's the other way around: the movement of the control surfaces is a response by the FBW to the of uneven surface of the runway.

Correct. It still does not redeem you, O 'Engineer', of that spectacular gaff about the F-22's rudder system being 'inferior' to the J-20's all moving vertical stabs.

In other words the FBW thinks that the movements of the plane due to uneveness of the runway as the plane's movements in flight and tries to correct it using the control surfaces?

Yes.

If the FBW were to actually counteract the undulating movement, instead of letting it be, the aerodynamic drag would be increased considerably. I saw the wild flipping of the control surfaces in only one of the many videos of J-20 taking off and I presumed it was part of the scheduled testings in the particular flight test.

Wrong. Aerodynamic drag has nothing to do with this.

Stability augmentation (stabaug) is not confined to fly-by-wire flight control system (FBW-FLCS). In its crudest form, whenever a pilot try to compensate for the inevitable in-flight turbulence, it is an attempt at stabaug. When he command a maneuver and the aircraft respond, as the pilot continues to hold the controls and strive to compensate for any 'roughness' during the maneuver, it is also an attempt at stabaug throughout the maneuver. We have been doing this since the biplane era. As the aircraft became more 'high performance' in speed, altitude, agility, and rate of response, the human factor at stabaug did not rise to match. In other words, we suck at stabaug and the result was many of us died in aviation's progress.

Entered electronics and hydraulics to take up where the human failed.

STRIKE - RAAF STYLE

Due to the nature of its role, the F-111 has a rather complicated flight control system, using hydromechanical actuators controlled by electrical signals from a stability augmentation system (SAS), that is in turn controlled by an autopilot slaved to the TFR computer. The SAS is analogue, using pitch rate and normal acceleration feedback, however the system employs self adaptive loop gain (this was chosen to cope with the multiplicity of CG /CP configurations associated with various fuel, wing sweep and stores configurations) and has some quirks, particularly in TF operation (this system was subsequently modified in later US versions).

Stabaug exists in hydro-mechanical FLCS like the F-111 and the F-15. So we can do away with any disputes about the fly-by-wire part being necessary for stabaug.

Computer controlled stabaug, fly-by-wire or electro-hydro-mech, is possible through a combination of inputs:

Fly-by-wire - Wikipedia, the free encyclopedia

Fly-by-wire control systems allow aircraft computers to perform tasks without pilot input. Automatic stability systems operate in this way. Gyroscopes fitted with sensors are mounted in an aircraft to sense movement changes in the pitch, roll and yaw axes. Any movement (from straight and level flight for example) results in signals to the computer, which automatically moves control actuators to stabilize the aircraft.

What the wiki source left out is an equally important factor: Air data.

GUIDANCE, NAVIGATION AND CONTROL

In atmospheric flight, flight control adjusts control sensitivity based on air data parameters derived from local pressures sensed by air data probes and performs turn coordination using body attitude angles derived from IMU angles. Thus, GN&C hardware required to support flight control is a function of the mission phase.

It does not matter if the aircraft is the Space Shuttle or the F-111. If there is atmospheric flight and computer controlled stabaug, air data is required: Airspeed and altitude. They came from pitot and static pressures respectively. The pitot probe on the F-16's radome is an example. The hole on the probe's tip is pitot or raw rammed air. There are smaller holes on the probe's underside for static pressure measurement. The 'Central Air Data Computer' (CADC), or equivalent in other aircrafts, processes these raw air data to give us computed airspeed, which include Mach number, and computed altitude.

NAE Website - Technology and the F-16 Fighting Falcon Jet Fighter

The resulting system is a quad-redundant (fail-operative, fail-operative, fail-safe), high-authority, command-and-stability augmentation system. The system consists of a series of sensors (accelerometers, rate gyros, air data converter), computers, selectors, transducers, and inverters that collectively generate the pitch, roll, and yaw rates that are transmitted as electronic signals to the five triplex electrohydraulic, servoactuators that control the flaperons (roll and flaps), elevons (pitch and roll), and rudder.

Regarding the conversation above where we observed the highly visible movements of the flight control surfaces during uneven ground travel. It does not matter if the aircraft is the J-20 or the F-111. What happens is that traveling over the uneven ground induces gyroscopes' and accelerometers' signal changes, the FLCS detects those changes and initiate stabaug, but since part of stabaug calculations to command the flight control surfaces require air data, as in airspeed and altitude, and because ground travel has practically none of those data, the FLCS deflects the surfaces to a higher degree.

It is an inverse relationship that we know since the beginning of aviation: That low airspeed require high surface deflection to initiate and sustain a maneuver. Any student pilot learned this from day one. No different when the computer take over stabaug and most of the responsibility of flight controls: Low air data will result in a higher deflection of the flight control surfaces. So on uneven ground travel with practically no air data, any gyro and accel inputs to the FLCS will result in very high surface deflections. Once there is weight-off-wheels and airspeed and altitude data increases, surface deflections becomes minimal, practically not visible, and yet still enough to push the human pilot to his maximum tolerance of 9g.

This is basic avionics engineering so stop all the speculations.

 

[Rizzy139]

Hi Gambit, I need your help - Im doing a project on Flight Control Systems and the images youve inserted on page 20 are perfect for what I need, please could you refer me to where you got them from?

Rizzy139 at hotmail.com

---------- Post added at 01:12 AM ---------- Previous post was at 01:11 AM ----------

In case you want to know why im asking, im a final year student of Aeronautical Engineering looking into the new PBW systems being used, for background research I need diagrams and the ones youve posted are perfect so I just need a source to reference., please help mate

 

[500]

I hope you are not trying to infer that the F-15 came from the MIG-25 in any stretch of the imagination. The truth is difficult to bear for many: The MIG-25 came from the North American A-5 Vigilante.

The A-5 originally had twin vertical stabs, which the US Navy at that time thought it was too 'radical' of a design. North American then redesigned the A-5 to have a single large vertical stab. The Soviets got a hold of the A-5's design, who knows how, and built the MIG-25. The F-15 also has the same parentage.

Twin tail A-5 Vigilante concept:

 

[ChineseTiger1986]

1. Advance engines are in making for J-20 with reduce IR signature as well as reduce harmonics generating from engine which is can be detected by radar too.

2. Engine reliability issues. Chinese have just mastered the engine technology so next is mass production which they lack right now kind of ,so in order to compensate all these, they use russian engines

The TH engine is in the state of mass production right now, and soon J-10B will be largely equipped with this engine.

BTW, JF-17 will eventually use WS-13 which will be ready for the next year.

 

[gambit]

J-20 5th Generation Fighter - Page 27

Here is a video about an alleged encounter between the Eurofighter and the F-22.

Eurofighter Typhoon beat the F-22 Raptor - YouTube

Pay attention to the part at 0:46 about how the F-22 was "unstealthed," thus it was detected by the Eurofighter. Maybe the F-22 didn't receive its maximum or optimum stealth coat/paint, thus, it wasn't as stealthy as expected.

There is convincing evidence that the F-22's initial stealth coat/paint was much more fragile than expected, it requires extra and special maintenance, and is constantly being improved.

Wrong. And it proved how gullible you really are. Bottom line is you do not know what the hell you are talking about.

What we call 'stealth' is nothing like an OFF/ON switch. The closest thing to such a switch is a radar enhancer that is removable...

The F-22 Is Battle Ready

The F-22 has a special feature that will allow it to be seen on radar when flying Noble Eagle and area training missions, Hecker said, but that feature is removed if the aircraft is going to war or practicing full-up. He declined to describe it, due to classification, but acknowledged that it is not unlike a special radar enhancer used on the F-117.

The device is called a 'Luneberg lens' and we have covered this device here before...

RCS Radar Cross Section, Lüneberg Reflector lensref - Luneburg radar

The Luneberg reflector significantly increases the Radar Cross Section (RCS) of any system which has little or none at all.

Its Radar Cross Section is several hundred times the RCS of a metallic sphere of same diameter.

There are many uses for radar enhancer in the civilian world. One of them is to install enhancers on tall radio transmitters for aviation safety purposes or in marine safety to highlight small objects on sea surfaces...

The West Advisor: Radar Reflectors

Radar Reflectors (more accurately called Radar Target Enhancers, or RTEs) reflect radar energy from other vessels' radars so that your boat shows up as a larger and more consistent "target". If you operate your boat in areas with shipping traffic or where fog and low visibility are common, the ability to be seen by radar-equipped ships can make the difference between being seen and being sunk.

The Luneberg lens device installed on the F-22 can be seen here...

http://www.codeonemagazine.com/images/media/20100805_F22_08052010_01_1267828237_2863.jpg
http://www.codeonemagazine.com/images/media/2010_001AFF_091119_0012_SM_1267828237_2127.jpg

It is that small cylinder on the aircraft's underside. The Luneberg lens device is chosen because of all enhancer designs, it offer the HIGHEST reflectivity towards any direction and it has the lowest aerodynamic drag. The B-2 and F-117 also routinely fly with enhancers to assist civilian traffic controllers.

In short, the Eurofighter pilots were picking up more of the enhancers and far less of the F-22 itself.

As far as any coatings applied to decrease surface reflectivity goes...

Perhaps the biggest question long posed about the F-22 has been its ability to operate like any other fighter, even though stealth technology has historically demanded meticulous care of aircraft surfaces, well beyond what could be managed at an austere expeditionary airstrip. In real-world F-22 operations, though, it has proved not to be an issue.

“We’ve made huge advancements as far as the coating application, the durability, and maintainability as a whole” of the F-22’s stealth systems, according to MSgt. Renee Daig, noncommissioned officer in charge of Langley’s Low Observable Composite Repair Facility.

She said the F-117 is considered first generation stealth, the B-2 was second generation, and the F-22 is third generation. The F-35 Joint Strike Fighter “will be considered the fourth generation,” she noted.

On the F-117, radar-absorbent material had to be fitted to the aircraft with virtually artistic skill, and any intrusion into a panel to repair a part caused huge downtimes as the material had to be painstakingly reapplied. On the B-2, things improved with the addition of more access hatches and panels, but the coatings and tape that sealed seams still posed a headache of reapplication after every mission.

By contrast, the F-22’s stealth systems can be fixed outside, on a ramp, not requiring substantial touch-ups for long periods of time, Daig said.

“Ninety-five percent of the restorations that we do on the aircraft we can do with a standard brush or roller,” she said. “Now, does that mean you can do it out on the open flight line? ... You sure can.”

Just as “you wouldn’t consider painting your house” in bad weather, the F-22’s LO maintainer also must use common sense, and “in a deployed environment, ... we would prefer to have some type of shelter or overhang” to work under. But it isn’t always necessary. Stealth materials were touched up on the Nellis ramp during a deployment last year because it was a sunny day, 70 degrees, and there was no wind, she noted.

But here is the clincher...

Rather than clean up every single defect after every mission—“whether it be missing material, a crack, disbond, delamination, what have you”—the F-22’s handlers aim to keep the aircraft stealthy within certain parameters. After every inspection, the surface defects are cataloged and fed into a computer program called the Signature Assessment System. From a “pristine” aircraft fresh from the factory with no stealth defects—zero percent stealth impact—the percentage of dings on each Raptor accumulates over time in the computer model.

“When it broaches the 80 percent mark, we start to think about ... doing some repairs to get us back where we need to be,” Daig explained.

The model system is a far cry from the F-117 and B-2, which both originally required elaborate measuring devices—sometimes instrumented flying ranges—to measure their stealth. The B-2 has since moved to a system similar to SAS.

The “effects of defects” model “works very well for us, because you can find yourself with 200 to 300 nicks, dings, and scratches on the aircraft and still be an LO platform and still meet your LO missions,” Daig asserted. After the SAS registers 100 percent, “we can no longer guarantee to that pilot that he’s where he needs to be” in terms of stealth, she said.

Put it another way: Maintainers can control how much scratches they can give the F-22's surfaces so they try to minimize that by wearing 'booties' when working on the aircraft. However, because some scratches will be created by flying there is an RCS 'peacetime tolerance' of when an F-22 is allowed to have over the baseline measurement before it must be 'reconditioned' to match that lower baseline. That is what that Signature Assessment System (SAS) is for. What it also mean is that even if the F-22 is completely devoid of absorber coating, its RCS through body shaping will still be a formidable goal to match by any aspiring 'stealth' fighter.

My advice: Instead of paying attention to fanboy Youtube vids, you should pay attention to your own ignorance and gullibility.

 

[Rizzy139]

Hi Gambit, please could you help me this is urgent, I really need to know where you obtained them images, ive been looking all over the internet with no luck , they are on page 20 of this forum and they display the flight control system, there are a few images ranging from mechanic FCS to FBW FCS.

please could you either reply on here or email me on rizzy139 at hotmail.com