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i.e. said:On nearly all the previous programs (j-10 included) they have a problem of engine coming up short eventually retarding the overall program,*
to avoid the pitfall this time, they actually started the engine program much eariler. with a techonology program modeled on the american (IHPTET/ADVENT) technology programs to boot. this is a big wide front push. from theoritical to material sci to tooling/manufacturing.*
“Stealth jet team proves its metal
Stephen Chen*
Jan 15, 2011 SCMP.com*
Metallurgist Shi Changxu won a top national science award yesterday for his contribution to the development of high-performance jet engines - three days after the first public test flight of the mainland's J-20 stealth fighter plane.*
Professor Shi, former director of the Chinese Academy of Sciences' Institute of Metal Research in Shenyang, developed several families of top-secret, heat-resistant alloys, according to mainland scientists working on jet engines.*
The secret alloys were developed decades ago, but because jet engine metals take a long time to test, Shi's alloys have only recently begun to be used in the mainland's jet engines.*
In 1955, Shi left his teaching post at the Massachusetts Institute of Technology and boarded a ship for the East. He was one of 30 or so Chinese scientists held by the United States government to prevent them from returning to communist China. Shi left the US about the same time as Qian Xuesen, a rocket scientist from the California Institute of Technology, who later founded the Chinese space programme.*
After he landed in Shanghai, Shi was immediately sent to Shenyang, a heavy industry base in the northeast province of Liaoning, to boost steel production. Beijing's relationship with Moscow then soured rapidly and the Russians stopped helping their old ally develop fighter jets. The military turned to Shi for help.*
With hard work, genius and luck, Shi not only came up with the required alloys using the traditional approach he learned in the West, but also devised something entirely new.*
The laboratory performance of the new alloys was so good that no one dared to use them. For safety concerns, plane designers stuck with traditional alloys for China's mass-produced jet engines, whose performance lagged significantly behind their overseas counterparts.*
Shi's alloys then began a long march for industrial acceptance. Only recently, with their application in some of the mainland's most advanced fighter jets such as the J-20, have designers fully accepted them.*
Professor Zhang Lanting, from the school of materials science and engineering at Shanghai Jiaotong University, said the mainland's aviation material science sector had been waiting too long for this award.*
Some people thought China did not have the materials to make high-performance jet engines, but they were wrong, Zhang said.*
"The fact is, we have lots of top-quality materials, but to convince plane designers to use them we need to test it for decades - normally 30 years - for absolute safety," he said. "Within 10 years Chinese engines will begin to replace foreign ones in the civilian sector. In the military sector the replacement has already begun."*
Professor Wu Suojun, a specialist in new materials at Beihang University, China's top aviation research institute, said the mainland was quickly narrowing the technological gap with the world's leading engine makers.*
"With the successful test flight of the J-20 and other new planes, it is time to reward the heroes behind the scenes," Wu said.
i.e. said:washout out the lift on the wing surface, so the span near tips would be less loaded than inboard spans. delay the wing tip stall AND boost aileron effectiveness at high AOAs.vistant said:Notice that too, what function does this twist perform in aerodynamics?
Now it would be more impressive if they did not have any washout at the tip.*, control configured washout via ailerons would be more cool.
with its up wing design? YES! that what I have been saying for days. and look at its MLG attachement point! structure wise it is pretty interesting.*BlauerMax said:*
The J-20's wing actually looks kinda similar to the X-32.
and onto those who said it is Mig 1.44 stealthrized. vs Flankerism of PAKFA:*
IT IS NOT MIG 1.44 Stealthrized.
the chief aerodynamicist, spelled out his entire ideas for this thing in a paper published in 90s.(?), (with quotes to Bill Sweetman to boot. ). this is not a Mig 1.44. reborn.
bill sweetman commented that this thing looks like have high wing loading.*
" Relative to Typhoon or Rafale, the wing appears more highly loaded and more sharply swept, favoring speed rather than ultimate agility. "*
*I told you so that people can fall for this.*
with closed coupled canard/lerx, the "looks" can be deceptive.*
They will go for both speed and manueverbility, that was always the goal.
If they really went for speed over manueverbility, the canards would come off and a compound delta would come in its place.
that was one of the original proposals actually.*
But, Mr. Song said "I can do both". so wola that's what you see today.
There will be some lift from the fuselage but not straight forward additions like Lift from Wing + lift from body = total lift. more like Lift from Wing + lift from body << total lift*StAndrea said:*
J-20 has a flat ventral body. So you have made a mistake in basic logical operation, deductive reasoning.
But you have made a mistake in premises too. Using space reentry vehicle body design example, assuming that's lifting body design fitted for fighter jets.
So it could be said that using two mistakes, first in logic, second in physics, you've probably came to the right conclusion.
in the case of fighters like J-20 usually you put your entire fighter VT and all into your wing tunnel and cfd this would give you complete wing+body total lift/drag/pitching moment characteristics.
now before this there will be configurations study where aerodynamicist would do experimental studies to see what the best configuration would be to attain your over all goal to satisfy some requirement. from that you narrow down to your final configurations.*
In song's paper his conclusion on lifting body is that the energetic vortices from LERX combine that from forebody would actually generate alot lift on rear portion of the fuselage. but a pan-cake like lifting body (i.e. a wide chorded short span wing if you will) is difficult to physically align with the canard configuration and have good internal volume for stores and all.*
Here is why I think the ventral fins are staying: they actually help to generate some lift by acting on the flap rear part pf fuselage like end-plates. think of it as channel flow between engines flanker style, but with out the wide mounted engines. and as the high energy regions on the rear bottom fuselage goes, they should also get more effective directional stability coming out from those fins... thus can shrink the requirement for those already smallish all moving VT.*
anyways, just as a reminder, drag is just as important as lift. and as an old expert might say: the best lift/drag is still a wing.*
It is of no import as you use it only to compare aircraft and you can freely choose the method appropriate to the aircraft you are comparing. Just don't forget what you are about.