Chinese Military Articles: Translation Thread


siegecrossbow

Brigadier
Staff member
Super Moderator
After hanging out on English language military forums for several years I noticed that most forum goers are frustrated by their inability to understand Chinese when some one moves an article from a mainland forum. Although sometimes members who are fluent in both English and Chinese would help out by translating segments of the article most of the time people have to rely on horrendous translations from google or yahoo to get a gist of the article. I am proposing a solution to this problem.

On another Chinese military forum I created a thread dedicated to the translation of Chinese language articles, forum posts, journals, etc. What I am envisioning is an organized effort that could reliably churn out readable translations of Chinese articles and help ease the language barrier between Chinese and English language forums.

This is our first attempt at translation. We've only done preliminary editing and it really shows... Feel free to give suggestions since any suggestion could help the translation process significantly.

Those who are interested in the translation process feel free to follow our progress at this link:
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Thnx in advance!

Here is the Chinese version of the article on J-20, written by Tianlong from CJDBY shortly following J-20's first flight:

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会当凌绝顶,一览众山小——二评中国第四代战斗机
天龙
二○一一年一月十五日

[1]
中国四代机计划产生的年代,正是中国空军主战装备从二代机向三代机转换的过程,在初尝三代机机动性能优越性 的甜头后,机动性、超机动成为中国空军的核心思想。因此,四代机四项目指标中的非常规机动、超音速机动、超 音速巡航成为不能打折的钢性指标。而此时,中国可以马上用于四代机的发动机只有俄罗斯的AL-31,国产的太行还处在试飞阶段,这两种发动机都是标准的三代发动机,实际推重比只能达到7.5左 右。

[2]
发动机落后于飞机设计,是中国航空界的老毛病了,在新中国的航空史上,规划中的飞机计划因发动机拖后腿无疾 而终的例子屡见不鲜;就拿著名的歼-10来说,如果不是及时采购俄罗斯的AL-31发动机,歼-10的成军至少还要延长很多年。

[3]
由于有前车之鉴,中国空军和航空制造部门都绝对不敢将中国四代机计划建立在图纸中的发动机上。退一步来说, 即使考虑到四代机配套发动机的因素,以中国的技术水平和资金投入,也只能制造出推重比9.5的发动机(号称 推重比10),距离美国推重比11的先进发动机,还是有相当大的差距。如何才能在发动机处于劣势的情况下, 使中国的四代机拥有与美国四代机同样的机动性能和超音速性能,或者至少要达到没有不能接受的差距,就成为摆 在中国四代机设计者面前的一大难题。

[4]
跨音速机动性与超音速性能是飞机设计中的一对传统矛盾,即前者需要大展弦比、小后掠角和较大的机翼相对厚度 ;而后者则需要小展弦比、大后掠角和较小的机翼相对厚度,两者很难兼顾。第三代战斗机在经过多方探讨后,采 用了放宽纵向静安定性余度、采用中等后掠角、中等展弦比机翼、机翼变弯装置等措施成功地解决了 这一对矛盾。

[5]
但四代机由于强调超音速巡航(发动机在最大状态的情况下,可以1.5以上M数飞行30分钟),对飞机超音速 阻力特性的要求更加苛刻(要求超音速阻力更小,这里涉及到飞机的展弦比、后掠角、机翼相对厚度以及机身切面 等指标);对飞机机动性所要求的低速最大升力系数特性(对的飞机展弦比、后掠角、机翼相对厚度等指标呈现出 与超音速性能完全相反的技术要求),也呈现出与超音速阻力特性更大的设计矛盾。

[6]
美国凭借强大的发动机技术,采取常规设计方案,即常规气动布局、中等后惊角(40%)、小展弦比(2.35 )、前缘襟翼等技术,较好地解决这一难题(即在总体布局不影响跨音速机动性能的前提下,飞机的推重比又能满 足超音速巡航的要求)。但中国发动机技术落后美国三十年,以中国目前的发动机技术,采用传统设计方案,是无 法解决亚跨音速机动性要求的升阻比与超音速巡航性能要求的阻力特性方面的巨大矛盾。

[7]
亚跨音速升阻比决定飞机的最大航程和盘旋性能,因此,中国四代机对亚跨音速升阻比的要求是绝对不会低于三代 机的;然而,由于四代机比三代机多了一个超音速巡航的要求(即发动机在最大状态下,飞机可以保持M1.5的 速度飞行),这就使得超音速巡航的阻力特性设计,成为中国四代机总体气动设计的临界点,即在气动外型和发动 机推重比确定的条件下,为满足四代机超音速巡航阻力特性的需求(最少要达到军方的最低要求1.×M数),必 须在某些方面牺牲亚跨音速升阻比对飞机气动设计的要求。中国四代机的机翼采用了50度后掠角、 以及比F-22A还要小的展弦比(大后掠角、小展弦比的气动布局通常对超音速阻力特性较好,但对低速度最大升力特性和 亚跨音速升阻特性不利),就是立足中国发动机技术条件,满足四代机超音速巡航阻力特性的设计临界点。但这种 在设计上对超音速阻力特性做出的让步,并不能说服中国军方同意降低对四代机亚跨音速升阻特性的要求;这种不 可调合的设计矛盾表明,继续遵循美国的设计思路研制四代机是行不通的,这就迫使中国四代机的设计者只能放弃 美国常规气动布局设计的成功经验(俄罗斯发动机技术强于中国,所以俄罗斯的四代机在经历一翻艰难的探索后又 回到追循美国设计思路的老路,当然也有一些局部创新,但总体布局依然离不开美国的影响),另行寻找新的解决 途径,走自己的路。

[8]
由于中国一直存在发动机方面的弱点,中国在研制三代机时,已寻求新的气动布局(鸭翼)来解决跨音速机动性能 与超音速性能方面的矛盾,而且,在机翼前缘翼襟的气动效率方面已经发挥到了极限,因此,歼-10气动布局亦不能满足中国四代机的要求。

[9]
成飞设计所又提出进一步放宽纵向静安定度来提升最大升力系数。成飞的研究表明,飞机的纵向静安定度由三代机 的3%进一步放宽到10%可产生可观的升阻特性收益,改善跨音速、超音速升阻特性和低速最大升力系数;但缺 点是会增大大迎角时的低头控制负担和飞控系统的复杂程度,所以只能适可而止。进一步放宽纵向静安定度的尝试 ,在权衡利弊后的总收益增量仍不能满足四代机对亚跨音速升阻特性的要求。

[10]
为此,成飞将研究重点放到鸭翼布局的进一步创新。

[11]
世界航空技术已证实,正常布局的飞机采用升力体布局,在增升方面,取得了良好的效果。但至今为止,还没有采 用一种鸭翼布局的战斗机采用了升力体布局,这不是没有人认识到升力体布局的巨大优势,而是鸭翼布局飞机一般 要遵循鸭翼空间位置高于机翼的设计要求,只有这样才能通过鸭翼对机翼的下洗,使用其脱体涡之间产生有利的耦 合来增加升力系数。而升力体布局从总体上难以满足这一要求(升力体设计鸭翼与机翼基本处于同一 水平位置)。

[12]
被超音速巡航阻力特性这个设计临界点逼上绝路的成飞,只能选择鸭翼升力体的试验,以求打开一条 新的通道。

[13]
在试验中成飞发现,采用升力体的边条鸭式布局飞机,只要鸭翼、边条、机翼的距离、安装角等等适当……,尽管 鸭翼的增升效果会有所降低,但总体的升力特性优于没有采用升力体的鸭式布局飞机,这一重大发现令中国四代机 的设计者兴奋不已!

[14]
进一步的研究表明:采用升力体边条翼鸭式布局的飞机,其升力特性不仅来自鸭翼、前边条和机翼脱体涡之间的纵 向耦合,而且与左右脱体涡的有利干扰有关,而正是后者在机身上诱导出相当可观的升力,为升力特性的改善作出 了巨大的贡献。

[15]
更为令人振奋的是,采用升力体边条翼鸭式布局布局,还可以选择更小的展弦比,这无疑可以减轻发动机性能方面 的压力。成飞在试验中发现,采用升力体边条翼鸭式布局,在大迎角条件下,升力体边条翼鸭式布局飞机的升力主 要集中在机身和内侧机翼上,在适当降低机翼展弦比后,最大升力系数出现不降反升的现象,这一发 现着实惊人!

[16]
在常规气动布局下,超音速阻力特性、低速最大升力特性和亚跨音速升阻特性是一对传统的矛盾体,飞机机翼形态 对超音速阻力特性的影响最为显著,小展弦比、大后掠角机翼的超音速阻力特性较好,但对低速最大升力系数和亚 跨音速阻力特性相当不利。比如米格-21,后掠角57度、展弦比2.22,其超音速性能相当好,低速性能就比较差。

[17]
但在升力体边条翼鸭式布局时,这一对飞机气动设计中的传统矛盾体,竟然在一定程度上成为了统一体!这个新发 现,使采用升力体边条翼鸭式布局的飞机可以选择比常规气动布局更小的展弦比(对提升低速性能的设计临界点相 当有利),而且低速性能比常规气动布局更好。这一重大发现使发动机技术相对比较落后的国家,有可能立足现有 技术,兼顾飞机超音速性能和低速大迎角性能,制造出成本更低的四代机。

[18]
成飞在航空气动方面的一系列重大新发现,不仅为中国四代机的成功奠定了坚实的技术基础;也为人类的航空事业 做出了巨大的贡献!这也是中国航空人第一次由航空技术的模仿者变成了创新者和领跑者。

[19]
亚跨音速度与超音速巡航升阻特性的矛盾解决了,接下来就是低速大迎角的控制问题,这涉及到四代机的非常规机 动性能。

[20]
F-22的大迎角控制和过失速机动,主要是通过矢量发动机来完成,但成飞在这方面对自己的要求很高。他们提出中 国四代机的大迎角控制要能够保证在矢量机构失效后,飞机能够从过失速迎角范围内安全恢复(这在很大程度上考 虑了中国矢量发动机技术的可靠性)。所以他们将大迎角飞行的非常规气动力控制装置列入研究计划 。

[21]
传统的观念认为,鸭翼的失速迎角为35度,这是以色列人提出来的,后来为各国所重视,法国的阵风就将最大迎 角限制在28度,中国的歼-10则限制在26度,所以航空界一般以为在大迎角性能方面,鸭翼不如常规布局,因为鸭翼的失速迎角限制了鸭 翼的大迎角性能。

[22]
然而,在过失速飞行中,中国试飞员确发现另一种现象,即歼-10的大迎角控制性能远超过苏-27(即歼-10在飞眼镜蛇机动时的角度超过了苏-27)。这一信息最早由雷强披露,但受到持有传统观念网友的广泛质疑。

[23]
成飞的研究成果,证明的雷强的说法。他们的研究报告提出:根据俯仰控制面相对于飞机重心的前后位置,飞机低 头的控制力分为两类:一类是加载类,即位于飞机重心之后的控制面,如平尾、后缘襟翼等,需要通过增加升力来 产生低头控制力距;一类是卸载类,即位于飞机重心之前的控制面,如鸭翼,是通过减小升力来产生低头控制力距 。在大迎角条件下,翼面产生的升力系数趋向饱和,所以加载类控制面的低头控制能力也趋向饱和,这是常规布局 大迎角控制力的一个天生的无法克服的缺点。而卸载类控制面(鸭翼)才是大迎角下有效的低头控制装置。中国四 代机的非常规(鸭翼)气动布局,使中国的四代机天生就享有大迎角低头控制的优势。

[24]
考虑到四代机综合增升效果和低头控制能力的需求,中国四代机的鸭翼面积放大到了××%量级、鸭翼的最大偏度 达到-××%。这一设计使中国的四代机拥有了比歼-10更为优秀的大迎角飞行性能,也使中国四代机大迎角飞行的非常规气动力控制装置远远优于F-22和T50。

[25]
机动性能的设计问题解决了,四代机进入了隐身设计与气动设计的融合。这里只介绍一个典型的例子 。

[26]
出于侧向隐身的需要,飞机的垂直尾翼必须向内或向外倾斜,已将从水平方向入射的雷达电磁波从其他方向反射掉 ,这种隐身的技术需要,促使设计者必须采用双垂尾。但双垂尾会损失最大升力系数,最大可损失0.4的量级。 这对于想尽办法提升升力系数的设计者而言,是个相当不利的坏消息。

[27]
由于垂尾的不利影响是与改善升力措施联系在一起的,所以很难从根源上杜绝。一般可采用调整垂尾面积、位置、 倾斜角、安装位置将不利影响降到最低。但调整倾斜角和安装角又受到最佳隐身效果的影响,必须服从隐身的需求 。所以,比较可行的还是整垂尾面积和位置。成飞的研究表明,减小垂尾面积和采用无垂尾布局,是一个值得研究 的方向。但鉴于无垂尾需要解决的技术难点比较多,成飞选择了减小垂尾面积的方式。

[28]
受飞机方向安定性的影响,垂尾面积是无法进一步的缩小,唯一的方式是采用全动式垂尾,这样可将垂尾的相对面 积降低一半左右;但垂尾过小会影响飞机的方向安定性,特别是大M数和大迎角飞行状态下影响更大。所以为维持 飞机的方向安定性,一般全动式双垂尾的相对面积也有个极限,不可能无限度的减小。

[29]
据成飞的介绍,经过优化后的全动式双垂尾垂直尾翼,对最大升力系数的不利影响降低到了0.1的量级,同时还 大大减轻了双垂直尾的结构重量(至少减轻了尾翼的结构重量40%以上)。

[30]
成飞对四代机最大升力系数的渴求和设计上的斤斤计较,使中国的四代机具备了最优秀的亚跨音速机 动性能。

[31]
成飞在四代机的设计中,除了相当重视飞机的亚跨音速性能外,对超音速阻力特性的优化也相当重视,除了在机翼 设计中选择有利于超音速阻力特性的大后掠角、小展弦比、小的机翼相对厚度外,也尽一切可能优化飞机的超音速 阻力特性。比如采用了较长的机身(甚至不惜牺牲结构重量对推重比的影响),又比如采用全动式垂直尾翼和DS I进气道等(通过减轻结构重量来提升推重比,尽最大可能减少发动机的进气损失等)。还有一个未加证实的消息 ,即中国四代机的进气道采用了可调节的DSI进气道,这对于进一步提升飞机的超音速性能无疑是相当重要的。 也说明成飞在四代机设计中的技术创新,达到了空前绝后的高度。

[32]
今天,当我们以喜悦的心情审视这架完全与群不同的四代机时,可曾知道,成飞的设计人员在技术落后的情况下, 为了攀登世界气动学的颠峰所付出的一切吗?他们的付出是完全有价值的,在他们的努力下,中国的四代机当之无 愧地攀上了世界航空界气动学的顶峰,达到“会当凌绝顶,一览众山小”的境界!

[33]
1月11日,中国四代机成功首飞,这是一个值得纪念的日子,它标志着中国航空事业进入世界三强。但是,我们 在高兴的同时也要看到,中国的四代机,是一架包含着太多技术创新的飞机,至今为止,还没有那个国家一次性将 这么多新技术融入一架飞机之中,升力体边条翼鸭式布局、可调节式DSI进气道、全动式垂直尾翼、大迎角飞行 非常规气动力控制装置、隐身性能等等,这些新技术、新发明能否达到试验室的标准值,还需要经过实践的检验, 还需要在试飞中不断修正和完善。可以预料的是,由于承载了太多的新技术、创新性发明,中国四代机的试飞将是 一个极为艰难和漫长的过程,其试飞的难度也将远远超过歼-10、F-22和T50。我们期待中国四代机的试飞早日成功!我们祝福试飞员早日将这架饱含技术人员心血和创新型高新 技术的四代机送入战斗部队!
 
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siegecrossbow

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Re: Translation of amateur Chinese military article, take a look!

This translation is the work of no_name, belowfreezing, and siegecrossbow.

China's fifth generation fighter project began during the same era when Fourth generation fighters supplanted Third and Second generation fighters as the Chinese Air Force's main battle gears. PLAAF’s positive experience with Fourth generation fighters’ superior maneuverability led to a reevaluation of PLAAF air doctrine based on maneuverability and super maneuverability. As a result of this, Fifth generation characteristics such as unconventional maneuverability, supersonic maneuverability, and supercruise became uncompromisable requirements for China's Fifth Generation Fighter. However, the two types of engines immediately available for China's Fifth generation fighter project are the Russian AL-31 and the indigenous engine still under development, the WS-10 engine. Both types of engines are conventional Fourth generation engines and could only reliably achieve thrust to weight ratios of around 7.5.

The issue of engine designs lagging behind aircraft designs is an old problem in China's aviation industry. Many aircrafts fail to leave the drawing board due to China's inability to develop suitable engines. Take the famous J-10 fighter, for example. If China did not purchase the Russian Al-31 engine in time it would have taken a lot longer for the plane to enter service.

Due to historical precedence of failed engine designs, the Chinese Air Force and Aircraft Manufacturers are afraid to build their Fifth generation fighter project on engines that are still on the drawing board. With China's technological capabilities and funds the Chinese could only produce engines with a thrust to weight ratio of around 9.5 (or a thrust to weight ratio of 10, if you round up.). Chinese engines are still far behind their American counterparts (which have thrust to weight ratios of around 11). As a result of this a major problem facing the Chinese designers is how to produce a fighter plane with the same maneuverability and supersonic performance as American Fifth generation fighters (or, at the very least, have no major disparities in performances).

Design requirements for transonic maneuverability always contradicted requirements for supersonic performance. The former demand wings with larger aspect ratio, smaller swept angle and greater thickness relative to its cord; the latter require wings with a smaller aspect ratio, larger swept angle and smaller relative wing thickness.

Since Fifth generation airplanes emphasize supercruise (the ability of an aircraft to travel at Mach 1.5 for 30 minutes at maximum engine output), supersonic aerodynamic shaping is even more important than those of previous planes. In the area of supersonic aerodynamic shaping, primary constraints include the aspect ratio of the wings, back sweep angle, relative wing thickness and cross sectional shape. Optimizing these parameters for supercruise has significant conflicts with the airplane’s requirement for max lift coefficient at low speeds.

The US leveraged its immense advantage in engine technologies and used a conventional aerodynamic configuration with a 40 degree back swept angle, a small aspect ratio of 2.35, and leading wing slats. This allowed it to successfully solve the problem of optimizing aerodynamic layouts for supersonic, transonic and subsonic speeds. However, because China's engine technology is 30 years behind that of the US, it is impossible for China to use conventional aerodynamic designs to solve the problem of optimizing subsonic maneuverability while maintaining good supercruise capabilities and lower supersonic drag.

Subsonic lift to drag ratio determines an aircraft's maximum range and turn performance. As a result, the Chinese fifth gen. fighter's demand for subsonic lift to drag ratio will not be lower than those of Fourth gen. fighters. Unlike most conventional Fourth gen. fighters, Fifth gen. fighters need to supercruise (the ability of an aircraft to maintain a cruising speed of M1.5 without engaging the afterburners). This means that research on supercruise drag characteristics is pivotal to the aerodynamic design of China's Fifth gen. fighter. In order to satisfy the Air Force demand for supercruise (at least achieve a supercruise speed of 1.XM), the Chinese Fifth gen. fighter must make some sacrifices in subsonic lift to drag ratio. The wings of China's fifth gen. fighter are swept backward at 50 degree angles and have a smaller aspect ratio than those of the F-22A (small aspect ratio wings swept at large angles usually have good supersonic drag characteristics but have poor low speed lift and transonic drag characteristics). This is the design threshold of a fifth generation fighter with supercruise capabilities given the restrictions imposed by China's engine technology. Yet the sacrifices made to improve supersonic drag performances did not convince the Chinese military to lower the Chinese Fifth Gen. Fighters subsonic lift to drag ratio requirements. This seemingly irreconcilable contradiction indicates that it is impossible for China to follow American design logic on her indigenous fighter. This forces China's Fifth Gen. fighter designers to give up America's proven conventional aerodynamic design (since Russia's engine technology was superior to that of China’s the Russians went back to using a conventional aerodynamic layout after many experiments. While it is true that the Russians added numerous innovative features on the T-50 the main aerodynamic layout show significant American influence) and pursue new solutions to this problem.

Due to china's weakness in the area of jet engine development, a new aerodynamic configuration (canard configuration) was chosen to resolve the conflicting requirements of her Fourth generation fighter for transonic maneuverability and supersonic performance. Designs involving both the canards and the leading edge slats already utilized the aerodynamic efficiencies of the airfoils to the maximum. As a result the aerodynamic design of J-10 cannot satisfy PLAAF's requirements for her Fifth generation fighter.

The CAC research institute decided to further relax the longitudinal static stability factor to increase the maximum lift coefficient. Data from the CAC shows that relaxing the longitudinal stability factor from 3% (Fourth generation fighter jets) to 10% results in significant improvements in lift to drag characteristics. Both transonic and supersonic lift to drag characteristics and the maximum lift coefficient value under low speed were improved. The improvements came at the expense of difficult pitch-up problems during high angle of attack maneuvers and a more complex flight control design. After weighing the pros and cons, it was decided that relaxing longitudinal static stability alone would not be enough to satisfy the requirements of a Fifth generation aircraft where transonic lift to drag ratio is concerned.

Because of this, the CAC institute decided to focus on improving the canard configuration with innovative new features.

International aviation technology indicates that conventional aircrafts employing liftbody configuration achieved excellent results in lift enhancement. However, no canard-configuration fighters employed the liftbody design. This is not because no one recognized the advantage of the liftbody configuration but the result of canard placement on canard-configuration aircrafts. Canard-configuration fighter designs generally place the canards above the wings to allow the downwash generated by the canards to interact with the wings. This allows the aircraft to use the interaction of the vortices to produce beneficial couplings that will enhance the lift coefficient. It is difficult for liftbody configurations to satisfy this condition (liftbody design requires the canards to be level with the wings).

Pursuit for supersonic cruise drag characteristics forced the CAC to tinker with the canard liftbody configuration to open a new path in its pursuit for a Fifth gen. design.

CAC discovered during experiments that although adopting the lift body canard configuration reduces the lift contributions from the canards, its overall lift performance is better than that of a non lift body canard aircraft as long as the canards, LERX, and wings were placed at proper distances and angles with respect to one another. The designers were thrilled by this discovery

Further studies indicate that canard configuration aircrafts employing liftbody and LERX derive lift not only from the longitudinal coupling between the canards and forward portion of the LERX with the wings’ shed vortices but also the benign interferences between left and right shed vortices. The latter adds significant lift to the aircraft and greatly contributes to the improvement of lift characteristics.

Even more encouragingly, aircrafts employing the liftbody LERX canard configuration could select smaller aspect ratios. This will, without a doubt, reduce pressure on engine performance. The CAC discovered after numerous experiments that candard configuration planes employing liftbody LERX could, under high AOA conditions, concentrate the lift on the plane's body and inner portions of the wings. After properly reducing the wings’ aspect ratio the highest lift coefficient actually increased instead of decreasing as predicted. This is an amazing phenomenon.

Under conventional aerodynamic configuration, supersonic drag, maximum lift under low speed, and transonic lift to drag ratio suffer from contradictory design requirements. Aircraft wing designs have the most significant effect on supersonic drag. Wings with mall aspect ratio and large sweep angles offer lower drag at supersonic speeds but are detrimental to the other two requirements. The Mig-21 is a good example of this since its wings, with a sweep angle of 57 degrees and an aspect ratio of 2.22, offers very good supersonic performance but worse performances at lower speed.

Under a lift body LERX canard configuration, however, these two traditional contradictions of aerodynamic design became, to a certain degree, reconcilable! The new discover of using liftbody LERX canard configuration allows the aircraft to select smaller aspect ratios than its conventional counterpart (very beneficial for raising the design threshold for low speed characteristics) while maintaining better low speed characteristics than conventional configuration aircrafts. This major discovery allow nations that are comparatively backwards in engine technology to use their available technology to build low cost Fifth gen. aircrafts while maintaining the said aircrafts’ supersonic and low speed high AOA capabilities.

The discovery CAC made in flight aerodynamics resulted not only in a firm technical base on which China's Fifth generation fighter project can build upon but also greatly contributed to the world wide aeronautic industry. This marks the first time that the Chinese aerospace industry moved from being a imitator of aerospace technology to an innovator and pioneer.

After solving issues related to transonic and supersonic drag to lift performance, the CAC must then solve the problem of maintaining aircraft control under low speed and high angle of attack. The solution involves the plane’s non-conventional maneuverability capabilities.

F-22's controllability at high AOA and post stall maneuverability are primarily accomplished by thrust-vectored engines. The CAC, however, has even higher standards in this area and proposed that the Chinese Fifth Gen. fighter should maintain control at high AOA even when the thrust-vectoring nozzles fail. This will allow the plane to recover safely within post-stall AOA parameters (the reliability of Chinese thrust-vectored engine was a major consideration). As a result they included unconventional aerodynamic control devices for high AOA flight in their research project.

Traditionally people believe that the post stall AOA for a canard-configuration aircraft is 35 degrees. The Israelis were the first to propose this and their proposal was taken seriously by many other countries. The French restricted Rafale's highest AOA at 28 degrees while the Chinese set the J-10’s AOA at 26 degrees. As a result the aviation community generally believes that canard configuration fighters are inferior to conventional configuration fighters in terms of high AOA capabilities since the canards’ post stall AOA restrictions severely limited the high AOA capabilities of canard configuration fighters.

Yet Chinese test pilots noticed something completely different during post stall flight. They discovered that J-10's high AOA control was far superior to that of the Su-27 (the J-10 achieved higher angles than the Su-27 during the cobra maneuver). This information was first leaked by test pilot Lei Qiang but widely questioned by military fans.

CAC's research confirms Lei Qiang's claims. Their research reports indicate that there are two types of negative pitch moment control surfaces depending on the positioning of the elevator with respect to the aircraft's center of mass. The first are the "load enhancing" control surfaces. They are control surfaces placed behind the aircraft's center of mass. Examples of this include horizontal stabilizers and trailing flaps which generate negative pitch moment by increasing lift. The second are the "load reducing" control surfaces. They are control surfaces placed in front of an aircraft's center of mass. "Load reducing" control surfaces include the canards, which generate negative pitch moment by decreasing lift. Under high AOA conditions the lift coefficient generated by the wings approach saturation and as a result the negative pitch moment of "load enhancing" control surfaces approach saturation as well. This problem, which is unsolvable by conventional configuration aircrafts at high AOA, could be effectively solved by "load reducing" control surfaces (canards). The unconventional (canard) configuration of China's Fifth gen fighter gives the Chinese fighter a "natural born" advantage at high AOA control.

Taking into consideration the needs of overall lift performance and better negative pitch control of the Fifth generation aircraft design, the areas of the canards are increased by xx%, and their largest deviation angles were increased to xx degrees. This design allows J-20 to have better high angle of attack aerodynamic performance than J-10. It is also superior to the T-50 and F-22 in terms of its high angle of attack unconventional aerodynamics control.

Having solved the issue of maneuverability, China’s Fifth Gen. Fighter must integrate RCS reduction measures into its aerodynamic design. I will only cover some prominent examples here.

Due to requirement for sideway stealth, the planes’ vertical stabilizers need to be canted either inwards or outwards to deflect horizontal radar waves in the other directions. This means that a twin-tail configuration is needed. However, a twin-tail design can reduce the maximum lift coefficient by as much as a factor of 0.4. This is very bad news for the designers whose focus is to increase the J-20’s lift capacity.

Since the negative impact vertical stabilizers have on stealth is offset by its benefit of lift improvement it is difficult to root out this problem. Ordinarily an aircraft designer could lower the negative impacts of the vertical stabilizers by adjusting the area, placement, tilt, and position of the said stabilizers. Yet modifications of the tilt and placement angles are effected by optimal RCS reduction and must comply with stealth considerations. As a result, it is more practical to alter the size and position of the vertical stabilizers. CAC's studies show that plans which decrease the size of the vertical stabilizers or eliminate them all together deserve further attention. Since there are many unresolved technical issues with the stabilizerless design, the CAC ended up picking the method which reduces the sizes of the vertical stabilizers.

Due to the aircraft's need to maintain directional stability it isn't possible for the design team to shrink the areas of the vertical stabilizers till they are within the required specs. The only way to go around this is to employ all moving vertical stabilizers, which allows the vertical stabilizers to half their areas. Vertical stabilizers that are too small, however, will negatively affect an aircraft's directional stability especially when the plane is flying at high Mach speeds or maneuvering at high AOA. In order to maintain the aircraft's directional stability there is usually a limit to the relative sizes of all moving vertical stabilizers. It is not possible to shrink them to infinitesimally small sizes.

CAC's research indicates that improved versions of twin vertical stabilizers decreases the negative impact to the max lift coefficient to the 0.1 level and, at the same time, reduces the structural weight of the vertical stabilizers (decreasing the structural weight of the vertical stabilizers by over 40%).

CAC's obsessive pursuit for its Fifth gen. plane's max lift coefficient and stringent attention to design details helped China's fifth gen. aircraft gain the best transonic maneuverability.

During the design process the CAC not only emphasized the aircraft's sub and transonic capabilities but also focused on improving its supersonic drag characteristics. Aside from choosing the wing shape with attributes such as large backward sweep angle, small aspect ratio, and relatively thin thickness that are beneficial to the aircraft's supersonic drag characteristics, the CAC also incorporated supersonic drag reducing measures on other parts of the plane. Examples of this include the elongation of the plane's body (at the expense of thrust to weight ratios due to the extra structural weight), the incorporation of all moving vertical stabilizers, and the implementation of DSI intakes (measures that lower pressure on the engines by enhancing the thrust to weight ratio via structural weight reduction). Unconfirmed information indicates that China's Fifth gen. fighter used what is known as an "adjustable DSI intake" which will, without a doubt, further enhance the aircraft's supersonic capabilities. Incorporations of such devices testify to CAC's innovative design.

As we happily examine this completely unique Fifth gen. fighter today, just how many of us actually know the dedication and sacrifices the CAC designers made, under backward technological conditions, to reach the peak of aerodynamic design? Their toils were not in vain and as a result of their hard work China's Fifth gen. fighter is now a worthy fighter capable of holding its own in the realm of fighter aircrafts.

January 11th, 2011, the day China's Fifth gen. fighter took off for the first time, is a date worthy of remembrance since it marks the Chinese aviation industry's ascension to one of the top three aviation industries of the world. However, as we celebrate we should also realize that China's Fifth gen. fighter is a plane incorporating too many technological innovations. Until now no other country incorporated so many new technologies on a single aircraft. Liftbody LERX canard configuration, adjustable DSI intake, all moving vertical stabilizers, unconventional aerodynamic control mechanism for high AOA flight, RCS reduction measure and other new technologies and innovations need to prove their worth during future test flights. Predictably, the test flight process for China's Fifth gen. fighter will be a long and arduous process and its difficulty level will far exceed those of the J-10, F-22, and T-50. As we eagerly anticipate the success of China's Fifth gen. fighter's test flight process we send the test flight pilot our best wishes and hope that this magnificent plane will enter service as soon as possible.
 

siegecrossbow

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Re: Translation of amateur Chinese military article, take a look!

Giving my thread a bump.

If you have any suggestions feel free to tell me. The translation still needs a lot of work and I need as much input as possible.
 

Bltizo

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Re: Translation of amateur Chinese military article, take a look!

Nice, translation really appreciated.

Can we have permission to post to other forums? You'll be cited of course
 

siegecrossbow

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Re: Translation of amateur Chinese military article, take a look!

Nice, translation really appreciated.

Can we have permission to post to other forums? You'll be cited of course
You are ENCOURAGED to post to other forums but preferably after I get more input on this thread. The translation is shoddy in some parts and the article doesn't flow too well.
 

Bltizo

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Re: Translation of amateur Chinese military article, take a look!

You are ENCOURAGED to post to other forums but preferably after I get more input on this thread. The translation is shoddy in some parts and the article doesn't flow too well.
Cheers -- i think you've all done a great job, it's very easy to read.

I suppose tian long is a big shrimp?
 
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siegecrossbow

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Re: Translation of amateur Chinese military article, take a look!

Cheers -- i think you've all dine a great job, it's very easy to read.

I suppose tian long is a big shrimp?
Thnx a lot! It is always encouraging to hear kind words.

Tianlong is actually not CJDBY's local big shrimp but I presume that he is a big shrimp on another forum???

There are many other technical papers better written than this one from CJDBY. Once we have a translation team of sufficient size (say 40-50 people) we may even be able to translate Pupu's Sunset over KNAPPOs series.
 

Bltizo

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Re: Translation of amateur Chinese military article, take a look!

Lol actually it might not be such a good idea to have this info to be translated -- doing so will probably make the job of western intelligence much, much easier given their previous track record :p
(now we wait to see who objects -- they are probably CIA XD )
 

siegecrossbow

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Re: Translation of amateur Chinese military article, take a look!

Lol actually it might not be such a good idea to have this info to be translated -- doing so will probably make the job of western intelligence much, much easier given their previous track record :p
(now we wait to see who objects -- they are probably CIA XD )
...And I am gonna be a suspect CIA if I disagree? :D

You don't really buy the bullock that Western Intelligence agencies really gather info from Chinese websites do you?
 

bd popeye

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Re: Translation of amateur Chinese military article, take a look!

Question, Why are the Chinese languages so difficult to translate into English?
 

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