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

[latenlazy]

info was posted on wmf,probably around mid-january 2012.

Wonder where wmf got their information.

 

[airsuperiority]

Wonder where wmf got their information.

If it's January 2012 information, odds are that it's updated. And since WS-15 isn't onboard yet, I won't trust anything that's been said quite just yet.

 

[hardware]

info come from high ranking plaaf later reprint in wmf,it was brief statement.if he refering ws-15,then it mean's that prototype engine already exist either late 2009 or early 2011.

 

[thunderchief]

The issue is reality is not that simple. With a complex part, such as one with a lot of concavities, the part made using traditional method would see welding of multiple parts together. A part made with joints is weaker than one made from a single piece, and must be designed to be bulkier from the start to account for the lost in strength. Your assumption suppose that the parts made by different methods would use the exact same design, but in reality the two methods would result in completely different designs. Moreover, even a 5% weight saving from your 4300 kg figure translates to a weight reduction of 215 kg. This is more than twice the amount of your 100 kg claim.

Look at the diagram in figure 1 in this pdf :

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.

Also , this pic :

You will see that most of the F-22 titanium parts are not that complex , they are basically flat panels designed to give structural strength to the plane . Yes , there are some concavities and some welding , but this is relatively small and we are talking about hundreds of kilograms , not thousands . I claimed that weight reduction with 3D printing would be around 100 kg , max 200 and I stand by that assumption - even if I made a mistake it is not such a big deal , less then a weight of average weapon F-22 or J-20 would carry .

What is self explanatory is that the Concorde can still supercruise despite its lower thrust-to-weight ratio compared to F-22. This shows thrust-to-weight ratio does not support your claim that J-20 cannot supercruise with AL-31 engines.

Well , if J-20 had a tin, pencil like shape of Concorde maybe it could supercruise even with AL-31 Unfortunately , J-20 doesn't look like Concorde and it is much more similar to F-22 or PAK FA - not a big surprise because they are all fifth gen fighters , not passenger planes

Maneuverability and flying straight are not mutually exclusive.

Yes they are . Most maneuverable planes (acrobatic planes) have thick stubby wings and fuselage . Fast planes have thin wings and thin fuselage and they cannot pull high g-s . Fighters tend to make compromise because they need both speed and maneuverability .

 

[thunderchief]

Actually it saves a tremendous amount of fuel, but go ahead and be pig-headed about it,,the aircraft is able to accelerate and maintain supersonic without engaging the AB, and that is supercruise, it was developed in order to function the aircraft with-out engaging AB, the real beauty of the F-22 is the ability to maintain supersonic cruise of approx. mach 1.8 for an extended period of time, rather than the full AB dash, which will very quickly deplete your prescious fuel, the guy hoping to run the F-22 down in Full AB will soon have to break-off, the F-22 will simply be GONE! The F-22 is a very "slick" aircraft, its top speed remains classified, but if it is offensive and enters the target area supersonic, delivers its weapons at supersonic and departs the area still supersonic, with-out AB, and as stealthy as it is, supercruise not only saves fuel, it saves aircraft and airmen, you prolly ought to lay off that Clint Eastwood movie?????
"real life", hummh??? brat

Some simple physics here . You have a plane with weight of 19000 kg and speed of 1000 km/h . You want to double that speed to 2000 km/h staying at the same height . Kinetic energy at 1000 km/h would be 9500 MJ , you need to raise that to 38000 MJ . Where from will this extra 28500 MJ ? From burning your fuel !

Using AB or not you would need to convert same amount of chemical energy (fuel) to kinetic energy (speed) . Advantage of not using AB is that you would waste less energy (fuel) on other things ,as military thrust is more energy efficient then full AB . Advantage of using AB is that you would accelerate faster . That is about it .

 

[thunderchief]

The Typhoon, with fourth gen EJ2000s engines can achieve super cruise with limited payload, yet the F35 with its fifth gen F135 cannot, there is simply no categorical limitation or cut off that says a fourth gen engine cannot achieve super cruise while a fifth gen engine can.

Typhoon has two engines and combined they are just slightly weaker than F-35 . On the other hand , F-35 is heavier and has more "bulky" profile . T/W advantage is on Typhoon's side

A J20 with AL31s may not be able to super cruise on dry thrust alone, but it would not be unreasonable to think that with a slight boost from the afterburners to punch through the sound barrier, a J20, which would have an airframe optimised for super cruise, cannot maintain level supersonic flight with dry thrust alone.

Possible , as even Su-27 with slight payload (or no payload) could achieve the same - break trough sound barrier with AB , and then cruise at 1.1-1.2 M on military power for prolonged time . But purist do not agree this is supercruise .

You claimed that J-20 cannot supercruise with Al-31 engines. You are now making your argument vague in an attempt to distract others from your originally flawed claims. It is not helping your argument in anyway.

I still claim J-20 cannot supercruise with AL-31 - ie break sound barrier without using AB .

 

[plawolf]

Typhoon has two engines and combined they are just slightly weaker than F-35 . On the other hand , F-35 is heavier and has more "bulky" profile . T/W advantage is on Typhoon's side

Which proves my point, not yours, that its not engine generation or TWR that determines if a plane can super cruise or not.

Possible , as even Su-27 with slight payload (or no payload) could achieve the same - break trough sound barrier with AB , and then cruise at 1.1-1.2 M on military power for prolonged time . But purist do not agree this is supercruise .

I still claim J-20 cannot supercruise with AL-31 - ie break sound barrier without using AB .

Well some 'purists' also insist that only M1.4 can be classed as super cruise for no other reason than because only the Raptor can do it. As far as I am concerned, 'purists' can make and stress any distinction all they want, but I do not really care about such petty differentiation for differentiation sake.

What I care about is real world operational capacity, and in that regard, using a little afterburner to achieve supersonic flight and then maintaining it with military thrust would give almost all the advantages of true super cruise, and that is good enough for me for initial production aircraft that will later be upgraded with a true super cruising engine at a later time.

 

[thunderchief]

Which proves my point, not yours, that its not engine generation or TWR that determines if a plane can super cruise or not.

T/W largely determines if plane could supercruise in the same plane category . Both F-22 and J-20 are designed for two engines (unlike F-35 ) so we should compare their respective engines on one-to-one basis . And I think that difference between AL-31 and F119 is obvious to everyone

Well some 'purists' also insist that only M1.4 can be classed as super cruise for no other reason than because only the Raptor can do it. As far as I am concerned, 'purists' can make and stress any distinction all they want, but I do not really care about such petty differentiation for differentiation sake.

What I care about is real world operational capacity, and in that regard, using a little afterburner to achieve supersonic flight and then maintaining it with military thrust would give almost all the advantages of true super cruise, and that is good enough for me for initial production aircraft that will later be upgraded with a true super cruising engine at a later time.

Well , if F-22 can supercruise at 1.7 M (and maybe even more ) and J-20 at 1.1-1.2 M guess which plane would have advantage in combat ? More energy always means more advantage , and historically faster fighters generally dominated over slower .

 

[kwaigonegin]

Some simple physics here . You have a plane with weight of 19000 kg and speed of 1000 km/h . You want to double that speed to 2000 km/h staying at the same height . Kinetic energy at 1000 km/h would be 9500 MJ , you need to raise that to 38000 MJ . Where from will this extra 28500 MJ ? From burning your fuel !

Using AB or not you would need to convert same amount of chemical energy (fuel) to kinetic energy (speed) . Advantage of not using AB is that you would waste less energy (fuel) on other things ,as military thrust is more energy efficient then full AB . Advantage of using AB is that you would accelerate faster . That is about it .

Only partially correct! it's like a car. A fuel efficient car may still still generate the same amount of kinetic energy but burning fuel at different rates. No different than your example but you forgot engine efficiency you were thinking strictly only kinectic energy.

You save a LOT of fuel by not going into AB. That is A FACT!
Now I'm sure using AB gets you to a designated Mach number much quicker however we're not discussion acceleration here but merely the ability to fly past Mach 1 and maintaning such a speed w/o engaging afterburners.

I guess what I'm trying to say is if you have an F-22 flying at say Mach 1.7 and a F-15 flying at the same speed maintained all the way till their destination.. the F-22 will burn less fuel than the Raptor! That is black and white proof.

 

[plawolf]

Look at the diagram in figure 1 in this pdf :

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.

Also , this pic :

You will see that most of the F-22 titanium parts are not that complex , they are basically flat panels designed to give structural strength to the plane . Yes , there are some concavities and some welding , but this is relatively small and we are talking about hundreds of kilograms , not thousands . I claimed that weight reduction with 3D printing would be around 100 kg , max 200 and I stand by that assumption - even if I made a mistake it is not such a big deal , less then a weight of average weapon F-22 or J-20 would carry .

Just where are you getting this 100-200kg weight saving figure from?

According to your own source titanium comprise 40% of the empty weight of the F22, so for an empty weight of 19,700kg, that's 7,880kg of titanium. A 100-200kg weight saving would only represent a 1.25-2.5% weight saving.

With the 40% weight savings given by the sources, that's 3,152kg of weight savings. Even if you half that to 20%, that is still 1,576kg of weight savings, and no one can argue that that would not make a significant difference.