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

[Engineer]

Now here, we are dealing in the nebulous netherworld, while you are the mathmatician/engineer, and I highly respect your opinion, theres no way an aft mounted delta is producing that much more lift, or all fighters would be thusly configured. There are good reasons the US and Russia abandoned the aft mounted delta in fighter aircraft, and to be very honest I highly suspect that you would agree with me that the forward fuselage of the J-20 and the F-22 are very similar in shaping and ability to produce lift, so while the canard increases lift on the forward fuse, its inclusion on the J-20 merely brings it into parity with the F-22. The F-22 has massive and far aft mounted horizontal stabs, with the addition of TVC, and its shorter length, and higher thrust to weight ratio, the Raptor's pitch transitions are most impressive. So, while the J-10, Rafael, or Eurofighter "could" be in the same league, there is no way the J-20 is producing that much more lift, and even if it were, agility comes from the ability to transition that lift very rapidly without creating massive amounts of drag. Respectfully, given your obvious credentials and good sence, Air Force Brat.

I am simply stating what's in the chart. As for J-10, Eurofighter and Rafale, they are indeed delta-canard but are not in the same league as they do not employ flat belly and massive LERX to enhance lift. From the same chart you can see J-20's configuration produce 1.21 times more lift than a simple delta-canard.

 

[Air Force Brat]

I am simply stating what's in the chart. As for J-10, Eurofighter and Rafale, they are indeed delta-canard but are not in the same league as they do not employ flat belly and massive LERX to enhance lift. From the same chart you can see J-20's configuration produce 1.21 times more lift than a simple delta-canard.

Well, I am confident this is likely true, all modern fighter aircraft and even some larger aircraft are attempting to create a lifting body configuration, and it is very obvious on the J-20 and T-50, and likely to a lesser extent on the F-22. For the record I have stated that Dr. Song is very honest, I never said he wasn't a good salesman, and he had to sell the J-20 to the people who would be designing/building/buying and operating it, every good engineer has to be a salesman, right eng?AFB

Off Topic: Man, I wish all you guys were here, Momma Donna made Lasagne, garden salad, and now hot brownies and icecream, I always think of you guys when I eat to much, it would be better to share, especially with you player, then we would both weigh 175, well I'd prolly weigh 185.

 

[Engineer]

The F-22 has TVC nozzles increasing turn rates, roll rates, and the tail is no fluke, it is also adding lift on a relaxed stability configuration.

Each design group chose compromisess.

Chengdu opted for canards adding lift at high AoA to the wing but at the expense of killing lift at cruise flight.
The F-22 does not kill lift at cruise flight as J-20 does with canards.

T-50 uses the integral configuration see the patent lift, you can see the central body generates lift, MiG-29 generates 40% extra lift just from the central body fuselage airfoil.
Add the levcon that controls the lift generated by the LEX and increases lift at high AoA

You can see the T-50`s patent about the fuselage lift
all configurations do have advantages and disadvantages, all compromise

Your claim that canard kills lift at cruise is entirely your own imagination. Dr. Song's paper includes a graph comparing the coefficient of lift for canard and traditional configuration at various angle of attack. The result shows that at low angle of attack that is cruise, canard configuration does not generate any less lift than a canard-less configuration:

In a way, the J-20 actually achieves similar goal as a sweep-wing design, but does so without any weight disadvantage. The extensive use of vortex interactions allows extra lift to be generated on demand without having to actually change the sweep of the wing. At slow speed, the canard not only deflects positively to maximize lift, but also induces stronger vortex as a result thus increases the lift generated by the wing.

Another advantage of canard configuration is it allows pitch control to be maintained at large angle of attack, something that is not possible with a traditional configuration because the tail would lose effectiveness. That is why F-22 and PAKFA need TVN, where as J-20 does not.

What these show is that J-20 engineers put a lot of work into aerodynamics; partly because they did not have faith in their own engine technologies, and partly because were unwilling to take compromise.

 

[Air Force Brat]

The F-22 has TVC nozzles increasing turn rates, roll rates, and the tail is no fluke, it is also adding lift on a relaxed stability configuration.

Each design group chose compromisess.

Chengdu opted for canards adding lift at high AoA to the wing but at the expense of killing lift at cruise flight.
The F-22 does not kill lift at cruise flight as J-20 does with canards.
T-50 uses the integral configuration see the patent lift, you can see the central body generates lift, MiG-29 generates 40% extra lift just from the central body fuselage airfoil.
Add the levcon that controls the lift generated by the LEX and increases lift at high AoA

Sorry Eng, I did not see your reply before I added my two cents, but you are indeed correct!
Mig actually the tail provides down force in normal cruise to keep the aircraft aerodynamically balanced, the canards do actually provide additional lift to the total lift produced by the aircraft, while there is no doubt the T-50 is state of the art as is J-20, there is nothing particularly radical or new in the T-50 design or construction,although the Lerx over the intakes are rather large, it is quite obviously a Sukhoi product, with lots of Flanker DNA.

The canards do not kill lift, they provide pitch control, and they add to the total lift produced by the aircraft throughout the speed range, one of their many advantages and one of the reasons Dr. Song has used them to add lift and increase the speed of pitch transitions throughout the speed range. ALL fighter aircraft of modern design incorporate "lifting body technology so that the fuselage configuration adds to the total lift produced and increase efficiencies.

 

[broadsword]

There's one thing about canards and horizontal stabilizer that's been bugging me and I hope you guys can help answer me.

By using the horizontal stabilizer to control pitch and angle of attack, is the g-force on the pilot far less than it would have been the case with canards because the pivot is near the cockpit and not at the rear of the plane? If it is true, is it one the chief reasons the Americans don't use canards?

 

[latenlazy]

There's one thing about canards and horizontal stabilizer that's been bugging me and I hope you guys can help answer me.

By using the horizontal stabilizer to control pitch and angle of attack, is the g-force on the pilot far less than it would have been the case with canards because the pivot is near the cockpit and not at the rear of the plane? If it is true, is it one the chief reasons the Americans don't use canards?

To put it simply, No.

 

[Air Force Brat]

That is true, as PAKFA simply reuses many of the ideas found on Su-27. The LEVCON is really just an oversized leading edge flap so happen to control vortex because the outboard end is exposed. The LEVCON cannot replace the functions of a canard, with pitch control being the prime example.

Chinese engineers want the J-20 to have low drag, high lift, does so without powerful engines and without compromise. The result is a low aspect ratio configuration which produces high lift and sounds contradictory when you first hear it. The approach is very complex due to all the interactions influencing one another, so the only compromise here is the choice of a very complex design over something less risky.



Which is why I refer to the J-20 as a very smart aeroplane, not only in design and execution, but in operation, as Dr. Song states the FBW is immensely complicated, and while I cannot wrap my pilots mind around the complex engineering intracacies, I recognize that as the aircraft operates through its different configurations and airspeeds the FBW has to change the logic and conform to the engineers design criteria for that configuration and airspeed. Adding the canards to the aft mounted delta solved many of the challenges of managing the aircraft and attaining the flying qualities Dr. Song and team went after in a very passionate way, but at the same time added to the further intracacies of the FBW, as I have also noted the aileron rolls of both aircraft are very clean on entry, during the actual roll, and the exit, which indicates that the computer "flys" the J-20 very well, with no "dishing out", which can easily occur as you enter or exit the actual roll. AFB

 

[Player99]

Hehe, this is a rarity: Regarding the "artwork" concept, even before reading his further explanation, I seem to understand or appreciate what Mig-29 (or that Russian) means better than you guys here, . And therefore I had no problem with it.

It's more an art than science only in that not only whatever choices you may make will mean compromises one way or the other, but also sometimes the different compromises due to different choices made will give an overall equal set of costs and benefits.

 

[Player99]

I totally understand your sentiment, man! Perhaps some day in our real retirement, we'll reunite over there and spend the rest of our years peacefully but with lotsa excitement? Regarding weight, I'm afraid I'll need to make a huge effort to go from 130 to 175. Hehe... As for Lasagne, how about Federal Express some over here just to show some sincerity?

 

[kwaigonegin]

Eurofighter ate F-22 thanks to highly offbored missiles and HMS, F-35 will use similar technologies and PAKFA plans to use jamming, raw radar power and higher speed and agility to eat F-22.

I thought it has been mentioned several times that within the constraints of the exercise the F-22 had to battle it up close and personal with the Typhoon. In that case you are right BUT that is not realistic in a real conflict.
An F-22 would've probably taken the eurofighter out in BVR engagement and the pilot won;t ever see who launched the Amraam.

If a Raptor ever gets to a knifefight with a 4.5 Gen type fighter the pilot has already made a huge error in judgement or something seriously have gone wrong.

In a real fight it is also unlikely a Raptor will ever fight alone. It will maximize it's capabilities using it's Low Probability of Intercept (LPI) Intra-Flight Data Link for data exchanges between other F-22s not to mention the Raptors will also be flying with assistance from E-3 Sentry, E-8 Joint STARS, and RC-135. When you take the entire system into consideration the Eurofighter (or any other fighter) will have minimal chance of surviving a fight.