J-20 5th Gen Fighter Thread IV (Closed to posting)

[MiG-29]

Wait, didn't the X-31 do the cobra a couple decades ago?

yes it did it with Thust vectoring, Su-27 does it without it, his statement is flawed, for an aircraft to go 120 deg AoA there are more things than canards or tailplanes.

In fact in the original Sukhoi patent for the airframe of Su-27, Su-35 and S-54, they mention the lifting body generates the forces capable to return the aircraft back from the cobra and the flight control system uses the tailplane to allow those forces to work out and bring the jet back from the cobra

Характер протекания процесса выхода самолета на предельный дин. определяется соотношением его веса (G), площади плановой проекции (S) несущего корпуса, продольного момента инерции (Jz), а также аэродемпфирующих и моментных характеристик. Аэродемпфирующая характеристика самолета определяется отношением площадей несущего корпуса перед и позади центра тяжести самолета. Моментная характеристика определяет величину прибавки момента на пикирование после перекладки стабилизатора в соответствующее положение.
4. Самолет по п.1, отличающийся тем, что он снабжен подвижным горизонтальным оперением, установленным на корневых наплывах в головной части фюзеляжа с возможностью установки в нейтральном положении под отрицательным углом при дозвуковом полете на сверхкритических углах атаки и турбулизации обтекающего потока, достаточной для минимизации несимметричности обтекания

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[Engineer]

When you show me a cobra by any aircraft with canards and delta wing we talk, no video has ever shown, too much talk little proof Su-27 has tailplanes and does the cobra.

in fact LERX do increase lateral stability as such Su-27 can do the cobra.
this source proves it

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Su-37, S-37 had tailplanes triplane configuration is proven the best configuration but for stealth is not good.

Cobra doesn't mean anything. It is merely an uncontrollable flight at high angle of attack that only lasts a few seconds, which is different to a sustained and controlled flight that can go on for minutes. MiG-29 and Su-27 cannot maintain control flight at high angle of attack without the aid of thrust vectoring. Fighter aircraft with canard can sustain flight at high angle of attack, and can do Cobra without problems. Rafale can do it without issue, as stated by ORENA

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. J-10 can do it as well,

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:

许多观众都把歼-10与苏27对比。苏27的招牌表演动作是“眼镜蛇”，歼-10也能表演，而且比它有更好的操控性。雷强介绍说：“它（指苏27）做“眼镜蛇”动作完全是靠速度来控制它的角度，速度小了，角度就小，但歼-10飞机可以由飞行员控制角度，我想让它多大，就可以飞到多大。”

Everyone likes to compare J-10 with Su-27. Su-27's signature maneuver is the "Cobra". J-10 can do it too, and does so with better controllability. Lei Qiang goes on to explain: "In a Cobra maneuver, Su-27 needs to use its speed to control its angle of attack. The lower the speed, the smaller than angle of attack. J-10 on the other hand has control over the angle of attack. I can achieve any angle of attack I desire.[/url]

 

[Engineer]

yes it did it with Thust vectoring, Su-27 does it without it, his statement is flawed, for an aircraft to go 120 deg AoA there are more things than canards or tailplanes.

In fact in the original Sukhoi patent for the airframe of Su-27, Su-35 and S-54, they mention the lifting body generates the forces capable to return the aircraft back from the cobra and the flight control system uses the tailplane to allow those forces to work out and bring the jet back from the cobra

Характер протекания процесса выхода самолета на предельный дин. определяется соотношением его веса (G), площади плановой проекции (S) несущего корпуса, продольного момента инерции (Jz), а также аэродемпфирующих и моментных характеристик. Аэродемпфирующая характеристика самолета определяется отношением площадей несущего корпуса перед и позади центра тяжести самолета. Моментная характеристика определяет величину прибавки момента на пикирование после перекладки стабилизатора в соответствующее положение.
4. Самолет по п.1, отличающийся тем, что он снабжен подвижным горизонтальным оперением, установленным на корневых наплывах в головной части фюзеляжа с возможностью установки в нейтральном положении под отрицательным углом при дозвуковом полете на сверхкритических углах атаки и турбулизации обтекающего потока, достаточной для минимизации несимметричности обтекания

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Aircraft that relies on tailplane lacks pitch authority at such high angle of attack. From

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:

A concentration of characteristic curves C[sub]m[/sub] for the tailplane setting angle φ[sub]t[/sub] being varied at post-critical AoA (i.e. very low sensitivity of pitch moment with respect to the tailplane setting angle) reflects the loss of effectiveness of a horizontal tail at higher AoA.

For aircraft with tailplane such as Su-27, recovery is achieved passively through aerodynamic means. The pilot has no control over the process.

The recovery from high angles of attack to the classical flight mode in a few seconds only is possible due to moving the center of pressure on main wing back and creating the strong nose-down aerodynamic pitching moment about the center of gravity.

Simply put, once the Cobra maneuver is initiated, pilot on a MiG-29 or Su-27 has no control of the aircraft for the rest of the maneuver unless the aircraft is equipped with thrust vectoring. A Cobra maneuver is not a sustained high angle of attack flight which 5-th generation aircraft and aircraft with canard can achieve.

 

[MiG-29]

Aircraft that relies on tailplane lacks pitch authority at such high angle of attack. Simply put, once the Cobra maneuver is initiated, pilot on a MiG-29 or Su-27 has no control of the aircraft for the rest of the maneuver unless the aircraft is equipped with thrust vectoring. A Cobra maneuver is not a sustained high angle of attack flight which 5-th generation aircraft and aircraft with canard can achieve.

The patent By simonov and obviously by Sukhoi, says the tailplane has to be positioned on a specific angle to reduce lateral yaw unstability and coning and the flight control system disengaged from automatic to manual to allow for a high pitch, in few words the flight control system is used to allow for very high pitch rate by allowing the tailplane to go to very high pitch rates and the rest is done the the integral configuration, which balances the lift in front and behind the center of gravity.


In fact is no prerequisite to have a canard, the Cobra can be done with configuration 1 with just tailplane (horizontal stabilizer), they mention canards are used on Su-35 and S-54 to increase further lateral stability.

So i will put you in few words Mikhail Simonov head designer of Su-27 says that tailplane plays a very importante part on the Cobra allowing high pitch rates and reducing lateral unstability by adequate positioning of it.

Моментная характеристика определяет величину прибавки момента на пикирование после перекладки стабилизатора в соответствующее положение

 

[siegecrossbow]

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New J-20 and J-10 flight video:

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Courtesy of 汉魂雄风from CJDBY.

 

[MiG-29]

Cobra doesn't mean anything. It is merely an uncontrollable flight at high angle of attack that only lasts a few seconds, which is different to a sustained and controlled flight that can go on for minutes. MiG-29 and Su-27 cannot maintain control flight at high angle of attack without the aid of thrust vectoring. Fighter aircraft with canard can sustain flight at high angle of attack, and can do Cobra without problems. Rafale can do it without issue, as stated by ORENA

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. J-10 can do it as well,

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:

Controlability around 50 degrees is attained by Su-27, no aircraft has controlability at 70-90 degrees simple is a fantasy of yours, simply becuse the vortices burst, all jets do brief incursions into high angle of attack of 60-120 deg of AoA in fact Eurofighter, is limited to 35 degrees in operational conditions and Gripen and Su-27 have regular flight characteristics at similar AoA.

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in fact a Eurofighter pilots puts it in simple words


The effectiveness of an air superiority fighter relies on the successful combination of a range of design elements including thrust-to-weight ratio, wing loading, avionics and weapons integration. Furthermore, : appropriate tactics and valuable aircrew training must be developed to exploit the full potential of the weapon system.

Typically, when time comes to decide how to achieve the required “nose pointing capability” for high thrust-to-weight ratio airplanes three solutions are on the table:

- extremely high short term sustained Angle of Attack values (characteristic of twin tailed airplanes);- High Off-Bore-Sight Weapons, preferably supported by Helmet Cueing;
- Thrust Vectoring.

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So basicly he says is either cobra or Thrust vectoring in aerodynamic terms or HMS and AIM-9X if you have a not so agile fighter like F-35

 

[Engineer]

The patent By simonov and obviously by Sukhoi, says the tailplane has to be positioned on a specific angle to reduce lateral yaw unstability and coning and the flight control system disengaged from automatic to manual to allow for a high pitch, in few words the flight control system is used to allow for very high pitch rate by allowing the tailplane to go to very high pitch rates and the rest is done the the integral configuration, which balances the lift in front and behind the center of gravity.

Your interpetation of the patent is wrong. The flight control is not used for anything. In fact, the flight control is purposely disengaged (shut off). If enabled, the flight control system would never have allowed the aircraft to goes to such high angle of attack. Once the Cobra maneuver has been initiated, the tailplane becomes ineffective until after the aircraft has been recovered.

In fact is no prerequisite to have a canard, the Cobra can be done with configuration 1 with just tailplane (horizontal stabilizer), they mention canards are used on Su-35 and S-54 to increase further lateral stability.

So i will put you in few words Mikhail Simonov head designer of Su-27 says that tailplane plays a very importante part on the Cobra allowing high pitch rates and reducing lateral unstability by adequate positioning of it.

Whether canard is a prerequisite to Cobra maneuver or not is irrelevant, since Cobra maneuver itself doesn't mean anything about controllability. A Cobra maneuver is not a sustained flight at high angle of attack. As shown in post #616, an airraft with canard can maintain controllability at 60° angle of attack, whereas MiG-29 and Su-27 cannot achieve such a feat. It is that simple.

 

[Air Force Brat]

5th generation aircraft are not only about stealth, but also about superior aerodynamics. Without canard, a 4th generation fighter without TVC can never hope to sustain flight at 50° AoA as the F-35 did. Not only that, but when installed with more powerful engines, 4th generation fighter still cannot compete with F-22 in supercruise performance. So contrary to your claim, 5th generation aircraft with their stealth actually have bigger flight envelope than most 4th generation aircraft.

The use of TVC has no relevance to stealth. Aircraft use TVC typically employ traditional configuration as well where the tailplane becomes ineffective at high angle of attack. As shown in the SAC engineer's writing, aircraft with canard have no such issue and can still maintain control at high angle of attack. Hence, aircraft with canard do not need TVC. This fact is not only illustrated by

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, but also illustrated by your own examples of Eurofighter's and Rafale's holding out against the F-22 during exercises.

You are exactly right about the superior aerodynamics Eng, for our little bro to equate the F-22 to the F-117 shows a distinct lack of visual discrimination, I also read his articles, for one an unnamed "pilot" is not a reliable source, and to claim the Eurofighter and Rafael are kinemetically superior to the Raptor, I believe I have read that the Typhoon's max AoA is 35 degrees, so here again the same old tired unsubstantiated anecdotal "stories" do not hold water in the real world of hard truth, the J-20, the Raptor, the T-50, and to a lesser extent the F-35 will all have very superior aerodynamics, I would remind all that the first three are A2A, air superiority birds, the F-35 is an Air to Ground platform as was the F-117, it has been designed to have equivalent agility to the F-16 which is very outstanding, the F-16 FBW being dialed back to prevent "sleepers". Prolly time to return this thread to the J-20 before we awaken the dark knight, so Eng where is 2003, anybody hearing anything????

 

[Engineer]

Controlability around 50 degrees is attained by Su-27, no aircraft has controlability at 70-90 degrees simple is a fantasy of yours, simply becuse the vortices burst, all jets do brief incursions into high angle of attack of 60-120 deg of AoA

Momentarily passing through an angle of attack of 50° during Cobra maneuver does not show case controllability, since Cobra maneuver without thrust vectoring is uncontrollable. From

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, we see that the tailplane of such Soviet fighter only remains effective up to 40° angle of attack, far from the 50° controlability which you have claimed.

It can be explained by loosing of effectiveness of control surfaces... In the range of AoA up to 35° the normal increases approximately linearly, then stabilises and practically the tail surface losses its effectiveness... This way, in the first approximation, one can assume that control surface is able to work effectively in range approximately ±40°.

in fact Eurofighter, is limited to 35 degrees in operational conditions and Gripen and Su-27 have regular flight characteristics at similar AoA.

The artificial limit is placed a few degrees before maximum lift is achieved to prevent stall from occuring. Stall means loss of controllability for an aircraft with tailplane, but not so for an aircraft with all moving canard. The placement of the limit is actually a good indication of the capability of the aircraft. The

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, which is lower than the limit on the Eurofighter. This indicates the Eurofighter with canard is aerodynamically superior.

in fact a Eurofighter pilots puts it in simple words
...

So basicly he says is either cobra or Thrust vectoring in aerodynamic terms or HMS and AIM-9X if you have a not so agile fighter like F-35

You have just explained why Su-27 and MiG-29 are inferior to new aircraft. The biggest marketing gimmicks right now with Russian aircraft are thrust vectoring, post-stall capability, and HMS. That is because the Su-27 and MiG-29 are 40-year-old designs that cannot compete with new aircraft in aerodynamics. The J-10 for example, beats the Su-27 reguilarily in exercises.

What is interesting is that the Eurofighter pilot spent majority of the rest of the article explaining how thrust vectoring is of little help.

Thrust Vectoring is one of the design elements that can contribute to create a certain advantage during close air combat by generating impressive pitch and yaw rates, but only in a limited portion of the flight envelope at velocities well below “corner speed”.

In simple terms, this means thrust vectoring is only useful close to stall or in post-stall situations.

However, Thrust Vectoring can also transform in a few seconds an energy fighter in a piece of metal literally falling off the sky, making it an easy prey for those who have been able to conserve their energy.

Moreover, Thrust Vector operation requires the pilot to “create the opportunity” for its usage, spending valuable time in manoeuvring the aircraft to achieve a suitable condition and managing the activation of the Thrust Vector Control.

If you are “defensive” and your aircraft has Thrust Vectoring, you can possibly outturn your enemy, but that most likely won’t prove to be a great idea: an energy fighter like the Typhoon will conveniently “use the vertical” to retain energy and aggressively reposition for a missile or gun shot. Also the subsequent acceleration will be extremely time (and fuel) consuming, giving your opponent the opportunity to tail chase you for ever, exploiting all its short range weapon array.

If you are “neutral”, when typically vertical, rolling and flat scissors would accompany the progressive energy decay, similarly performing machines would remain closely entangled, negating the opportunity for Thrust Vector activation.

If you are “offensive”, probably stuck in a never ending “rate fight”, Thrust Vector could provide the opportunity for a couple of shots in close sequence. Make sure nobody is coming to you from the “support structure”, otherwise that could be also your last move.

This is basically what me and others have been saying all along: an aircraft with thrust vectoring goes into post-stall and gets killed faster.

 

[Engineer]

You are exactly right about the superior aerodynamics Eng, for our little bro to equate the F-22 to the F-117 shows a distinct lack of visual discrimination, I also read his articles, for one an unnamed "pilot" is not a reliable source, and to claim the Eurofighter and Rafael are kinemetically superior to the Raptor, I believe I have read that the Typhoon's max AoA is 35 degrees, so here again the same old tired unsubstantiated anecdotal "stories" do not hold water in the real world of hard truth, the J-20, the Raptor, the T-50, and to a lesser extent the F-35 will all have very superior aerodynamics, I would remind all that the first three are A2A, air superiority birds, the F-35 is an Air to Ground platform as was the F-117, it has been designed to have equivalent agility to the F-16 which is very outstanding, the F-16 FBW being dialed back to prevent "sleepers".

AoA limit is not to be confused with maximum attainable AoA. The former is merely computer code introduced by the engineers for good handling characteristics and safety, whereas the latter is related to physical limitations of the airframe.

With the limit in place, all the pilot has to do is pull the stick all the way back and the computers automatically fly the aircraft at the AoA limit. The limit coincides with where maximum lift occurs and enables the aircraft to achieve the best turn rate. Flying at larger AoA than the limit will only cause the amount of lift to drop and reduce turn rate, so why bother?

Prolly time to return this thread to the J-20 before we awaken the dark knight, so Eng where is 2003, anybody hearing anything????

The last few rumors from months ago are these:

• J-20 is undergoing some redesign of the internal structures.
• SAC, in their usual incompetence, did not give best effort on their part of the J-20 design.

Putting the two together and one may infer CAC is doing some redesign on the aft fuselage structure. That may explain the delay of 2003, if there is one.