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China helicopter passes cold weather flight test--XINHUA   [Copy link] 中文

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Post time 2012-2-14 04:25:45 |Display all floors
This post was edited by SMITHI at 2012-2-14 04:47

China helicopter passes cold weather flight test

English.news.cn   2012-02-13




TIANJIN, Feb. 13 (Xinhua) -- China's first independently-developed large civil helicopter, the AC313, has passed a cold weather flight test, establishing a good performance in polar region temperatures, said the producer -- China Aviation Industrial Helicopter Co. (CAIH) -- on Monday.
The flight testing period for the 13-tonne AC313 was conducted in Hulunbuir City, Inner Mongolia, starting in January, when the region experienced temperatures of minus 46 degrees Celsius.
The helicopter also set its speed record of 336 km per hour during the testing period.
The AC313 became the first China-made aircraft authorized by China's civil aviation authority in January to fly in high-altitude regions of over 4,500 meters above the sea level.
Xu Chaoliang, the chief designer of the helicopter, said the company has so far received 32 orders for it.
He said equipped with advanced instrument landing system, the helicopter can be used for disaster relief even in blizzard weather in plateau regions.
CAIH, a wholly owned subsidiary of the China Aviation Industry Corp., is expected to produce 300 helicopters annually by 2015, making it one of the major helicopter suppliers in the world.
Headquartered in Tianjin, the company is mainly engaged in the research and development, production, maintenance and sales of helicopters and other aircraft and aviation components.

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Post time 2012-2-14 07:03:09 |Display all floors
While I'm one who has ever any interest in civil aviation unless it's
in the nature of the Comac C919, I however am a diehard fan/enthusiats of military
aviation and I thought some of my compatriots here would be interested to dwell into this
a little. Link not attached due to the sensitiveness of the contents.

Certain portions of the following copy and paste has been changed due ti its sensitive nature.

As follow:

成飞设计所:  歼-二十 远远优于美国猛禽俄国火狐

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。

  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。

  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。

  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、以及比美国猛禽还要小的展弦比(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。

  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。

  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。

  为此,成飞将研究重点放到鸭翼布局的进一步创新。

  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)。

  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。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!

  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。

Putin's a killer. This was the claim made by Fox News journalist; Bill O'Reilly during his recent interview with Donald Trump. Trump's reply came in the form of a simple question. What, you think our country's so innocent?

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Post time 2012-2-14 10:17:49 |Display all floors
This post was edited by cestmoi at 2012-2-14 10:19

Marrying an excellent old French design, the Super Frelon, with new technologies... interesting approach.

As I have said before, I'd be interested in hearing more about the rotor blades and the rotor head. The French had difficulties manufacturing the rotor head back in the early 70s, but since China is using more recent technologies, AC313 might not have the same problems 40 years later... hopefully.

The Pratt & Whitney PT6B is a very reliable and robust unit. Going forward, it is more effective to have two rather than three engines.

China has chosen well.
Let the dice fly high

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Post time 2012-2-14 12:00:34 |Display all floors
cestmoi Post time: 2012-2-13 18:17
Marrying an excellent old French design, the Super Frelon, with new technologies... interesting appr ...

  
http://www.chnqiang.com/article/2012/0214/mil_58469.shtml
Putin's a killer. This was the claim made by Fox News journalist; Bill O'Reilly during his recent interview with Donald Trump. Trump's reply came in the form of a simple question. What, you think our country's so innocent?

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Post time 2012-2-14 14:44:41 |Display all floors
cestmoi Post time: 2012-2-14 10:17
Marrying an excellent old French design, the Super Frelon, with new technologies... interesting appr ...

excelent post very informative and obviously you know stuff , how do you know it is French design?

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Post time 2017-5-3 14:13:04 |Display all floors
SMITHI Post time: 2012-2-14 14:44
excelent post very informative and obviously you know stuff , how do you know it is French design?

After immigrating to the United States in 1919, Sikorsky founded the Sikorsky Aircraft Corporation in 1923, and developed the first of Pan American Airways' ocean-conquering flying boats in the 1930s.

In 1939, Sikorsky designed and flew the Vought-Sikorsky VS-300, the first viable American helicopter, which pioneered the rotor configuration used by most helicopters today. Sikorsky modified the design into the Sikorsky R-4, which became the world's first mass-produced helicopter in 1942.

The French inventor Etienne Oehmichen built and flew a helicopter one kilometer in 1924. Another early helicopter that flew for a decent distance was the German Focke-Wulf Fw 61, invented by an unknown inventor.

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Post time 2017-5-9 10:07:04 |Display all floors
emanreus Post time: 2017-5-3 14:13
After immigrating to the United States in 1919, Sikorsky founded the Sikorsky Aircraft Corporation ...

We all know who invented the FW64 it was a propaganda machine nothing more

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