鐵之狂傲

標題: 『每日軍事武器鑑賞』－ X-29 前掠翼試驗機 [列印本頁]

作者: 克里斯Chris 時間: 07-5-16 17:32
標題: 『每日軍事武器鑑賞』－ X-29 前掠翼試驗機
The X-29

Two X-29 aircraft, featuring one of the most unusual designs in aviation history, were flown at the NASA Ames-Dryden Flight Research Facility (soon to be renamed the Dryden Flight Research Center), Edwards, Calif., as technology demonstrators to investigate advanced concepts and technologies. The multi-phased program was conducted from 1984 to 1992 and provided an engineering data base that is available in the design and development of future aircraft.

The X-29 almost looked like it was flying backward. Its forward swept wings were mounted well back on the fuselage, while its canards horizontal stabilizers to control pitch were in front of the wings instead of on the tail. The complex geometries of the wings and canards combined to provide exceptional maneuverability, supersonic performance, and a light structure. Air moving over the forward-swept wings tended to flow inward toward the root of the wing instead of outward toward the wing tip as occurs on an aft swept wing. This reverse air flow did not allow the wing tips and their ailerons to stall (lose lift) at high angles of attack (direction of the fuselage relative to the air flow).

The concepts and technologies the fighter-size X-29 explored were the use of advanced composites in aircraft construction; variable camber wing surfaces; the unique forward-swept wing and its thin supercritical airfoil; strake flaps; close-coupled canards; and a computerized fly-by-wire flight control system to maintain control of the otherwise unstable aircraft.

Research results showed that the configuration of forward swept wings, coupled with movable canards, gave pilots excellent control response at up to 45 degrees angle of attack. During its flight history, the X-29's were flown on 422 research missions 242 by aircraft No. 1 in the Phase 1 portion of the program; 120 flights by aircraft No. 2 in Phase 2; and 60 flights in a follow-on "vortex control" phase. An additional 12 non-research flights with X29 No. 1 and 2 non-research flights with X-29 No. 2 raised the total number of flights with the two aircraft to 436.

作者: 克里斯Chris 時間: 07-5-16 17:32

Reverse airflow-forward-swept wing vs aft swept wing. On the forward-swept wing, ailerons remained unstalled at high angles of attack because the air over the forward swept wing tended to flow inward toward the root of the wing rather than outward toward the wing tip as on an aft-swept wing. This provided better airflow over the ailerons and prevented stalling (loss of lift) at high angles of attack.

作者: 克里斯Chris 時間: 07-5-16 17:33
Program History

Before World War II, there were some gliders with forward-swept wings, and the NACA Langley Memorial Aeronautical Laboratory did some wind-tunnel work on the concept in 1931. Germany developed a motor-driven aircraft with forward-swept wings during the war known as the Ju-287. The concept, however, was not successful because the technology and materials did not exist then to construct the wing rigid enough to overcome bending and twisting forces without making the aircraft too heavy.

The introduction of composite materials in the 1970's opened a new field of aircraft construction, making it possible to design rugged airframes and structures stronger than those made of conventional materials, yet lightweight and able to withstand tremendous aerodynamic forces.

Construction of the X-29's thin supercritical wing was made possible because of its composite construction. State-of-the-art composites permit aeroelastic tailoring, which allows the wing some bending but limits twisting and eliminates structural divergence within the flight envelope (i.e., deformation of the wing or breaking off in flight).

In 1977, the Defense Advanced Research Projects Agency (DARPA) and the Air Force Flight Dynamics Laboratory (now the Wright Laboratory), Wright-Patterson AFB, Ohio, issued proposals for a research aircraft designed to explore the forward swept wing concept. The aircraft was also intended to validate studies that said it should provide better control and lift qualities in extreme maneuvers, and possibly reduce aerodynamic drag as well as fly more efficiently at cruise speeds.

From several proposals, Grumman Aircraft Corporation was chosen in December 1981 to receive an $87 million contract to build two X-29 aircraft. They were to become the first new X-series aircraft in more than a decade. First flight of the No. 1 X-29 was Dec. 14, 1984, while the No. 2 aircraft first flew on May 23, 1989. Both first flights were from the NASA Ames-Dryden Flight Research Facility soon to be renamed the Dryden Flight Research Center.

作者: 克里斯Chris 時間: 07-5-16 17:33
Flight-Control System

The flight control surfaces on the X-29 were the forward-mounted canards, which shared the lifting load with the wings and provided primary pitch control; the wing flaperons (combination flaps and ailerons), used to change wing camber and function as ailerons for roll control when used asymmetrically; and the strake flaps on each side of the rudder that augmented the canards with pitch control. The control surfaces were linked electronically to a triple-redundant digital fly-by-wire flight control system (with analog back up) that provided an artificial stability.

The particular forward swept wing, close-coupled canard design used on the X-29 was unstable. The X-29's flight control system compensated for this instability by sensing flight conditions such as attitude and speed, and through computer processing, continually adjusted the control surfaces with up to 40 commands each second. This arrangement was made to reduce drag. Conventionally configured aircraft achieved stability by balancing lift loads on the wing with opposing downward loads on the tail at the cost of drag. The X-29 avoided this drag penalty through its relaxed static stability.

Each of the three digital flight control computers had an analog backup. If one of the digital computers failed, the remaining two took over. If two of the digital computers failed, the flight control system switched to the analog mode. If one of the analog computers failed, the two remaining analog computers took over. The risk of total systems failure was equivalent in the X-29 to the risk of mechanical failure in a conventional system.

X-29 - designed with relaxed static stability to achieve less drag, more maneuverability, increased fuel efficiency. Arrows in upper illustration indicate drag-producing opposing downward forces on rear stabilizers to achieve stability. X-29 canards share lifting loads, reducing drag.

作者: 克里斯Chris 時間: 07-5-16 17:33
Phase 1 Flights
The No. 1 aircraft demonstrated in 242 research flights that, because the air moving over the forward-swept wing flowed inward, rather than outward as it does on a rearward-swept wing, the wing tips remained unstalled at the moderate angles of attack flown by X-29 No. 1. Phase 1 flights also demonstrated that the aeroelastic tailored wing did, in fact, prevent structural divergence of the wing within the flight envelope, and that the control laws and control surface effectiveness were adequate to provide artificial stability for this otherwise extremely unstable aircraft and provided good handling qualities for the pilots.

The aircraft's supercritical airfoil also enhanced maneuvering and cruise capabilities in the transonic regime. Developed by NASA and originally tested on an F-8 at Dryden in the 1970s, supercritical airfoils flatter on the upper wing surface than conventional airfoils delayed and softened the onset of shock waves on the upper wing surface, reducing drag. The phase 1 flights also demonstrated that the aircraft could fly safely and reliably, even in tight turns.

作者: 克里斯Chris 時間: 07-5-16 17:33
Phase 2 Flights

The No. 2 X-29 investigated the aircraft's high angle of attack characteristics and the military utility of its forward-swept wing/canard configuration during 120 research flights. In Phase 2, flying at up to 67 degrees angle of attack (also called high alpha), the aircraft demonstrated much better control and maneuvering qualities than computational methods and simulation models had predicted. The No. 1 X-29 was limited to 21 degrees angle of attack maneuvering.

During Phase 2 flights, NASA, Air Force, and Grumman project pilots reported the X-29 aircraft had excellent control response to 45 degrees angle of attack and still had limited controllability at 67 degrees angle of attack. This controllability at high angles of attack can be attributed to the aircraft's unique forward-swept wing- canard design. The NASA/Air Force-designed high-gain flight control laws also contributed to the good flying qualities.

Flight control law concepts used in the program were developed from radio-controlled flight tests of a 22-percent X-29 drop model at NASA's Langley Research Center, Hampton, Va. The detail design was performed by engineers at Dryden and the Air Force Flight Test Center at Edwards. The X-29 achieved its high alpha controllability without leading edge flaps on the wings for additional lift, and without moveable vanes on the engine's exhaust nozzle to change or "vector" the direction of thrust, such as those used on the X-31 and the F-18 High Angle-of-Attack Research Vehicle. Researchers documented the aerodynamic characteristics of the aircraft at high angles of attack during this phase using a combination of pressure measurements and flow visualization. Flight test data from the high-angle-of-attack/military-utility phase of the X-29 program satisfied the primary objective of the X-29 program to evaluate the ability of X-29 technologies to improve future fighter aircraft mission performance.

作者: 克里斯Chris 時間: 07-5-16 17:33
Vortex Flow Control

In 1992 the U.S. Air Force initiated a program to study the use of vortex flow control as a means of providing increased aircraft control at high angles of attack when the normal flight control systems are ineffective.

The No. 2 X-29 was modified with the installation of two high-pressure nitrogen tanks and control valves with two small nozzle jets located on the forward upper portion of the nose. The purpose of the modifications was to inject air into the vortices that flow off the nose of the aircraft at high angles of attack.

Wind tunnel tests at the Air Force's Wright Laboratory and at the Grumman Corporation showed that injection of air into the vortices would change the direction of vortex flow and create corresponding forces on the nose of the aircraft to change or control the nose heading.

From May to August 1992, 60 flights successfully demonstrated vortex flow control (VFC). VFC was more effective than expected in generating yaw (left-to-right) forces, especially at higher angles of attack where the rudder loses effectiveness. VFC was less successful in providing control when sideslip (relative wind pushing on the side of the aircraft) was present, and it did little to decrease rocking oscillation of the aircraft.

作者: 克里斯Chris 時間: 07-5-16 17:34

Vortex flow control involves pneumatic manipulation of forebody vortices as shown in the diagram. Exhausting air through the nozzles at the top of the airplane's forebody results in alteration or movement of the forebody vortices. As the diagram shows, air exhaused through the right nozzle accelerates the flow of the right vortex and pulls it closer to the forebody. As this occurs, the left vortex is pushed further away from the body. This results in lower pressure on the side of the blowing right nozzle, resulting in a right yawing movement of the aircraft as shown.

作者: 克里斯Chris 時間: 07-5-16 17:34
Summary

Overall, VFC, like the forward-swept wings, showed promise for the future of aircraft design. The X-29 did not demonstrate the overall reduction in aerodynamic drag that earlier studies had suggested, but this discovery should not be interpreted to mean that a more optimized design with forward-swept wings could not yield a reduction in drag. Overall, the X-29 program demonstrated several new technologies as well as new uses of proven technologies. These included: aeroelastic tailoring to control structural divergence; use of a relatively large, close-coupled canard for longitudinal control; control of an aircraft with extreme instability while still providing good handling qualities; use of three-surface longitudinal control; use of a double-hinged trailing-edge flaperon at supersonic speeds; control effectiveness at high angle of attack; vortex control; and military utility of the overall design.

The Aircraft

The X-29 is a single-engine aircraft 48.1 feet long. Its forward-swept wing has a span of 27.2 feet. Each X-29 was powered by a General Electric F404-GE-400 engine producing 16,000 pounds of thrust. Empty weight was 13,600 pounds, while takeoff weight was 17,600 pounds.

The aircraft had a maximum operating altitude of 50,000 feet, a maximum speed of Mach 1.6, and a flight endurance time of approximately one hour. The only significant difference between the two aircraft was an emergency spin chute deployment system mounted at the base of the rudder on aircraft No. 2. External wing structure is primarily composite materials incorporated into precise patterns to develop strength and avoid structural divergence. The wing substructure and the basic airframe itself is aluminum and titanium. Wing trailing edge actuators controlling camber are mounted externally in streamlined fairings because of the thinness of the supercritical airfoil.

Program Management

The X-29 program was funded initially by the Department of Defense Advanced Research Projects Agency. The program was managed by the Air Force's Wright Laboratory, Aeronautical Systems Division, Air Force Systems Command, Wright-Patterson AFB, Ohio.

The flight research program was conducted by the Dryden Flight Research Center, and included the Air Force Flight Test Center and the Grumman Corporation as participating organizations.

作者: 克里斯Chris 時間: 07-5-16 17:36

VRML 3-D Model

X-29

(文章來自：獨樹一幟的前掠翼戰鬥機）

作者: 克里斯Chris 時間: 07-5-16 17:36
前掠翼戰鬥機的發展始終像一團迷，前掠翼結構是一種高度不穩定空氣動力學外形，目前只有俄羅斯和美國進行過深入研究。對前掠翼戰鬥機人們始終處於期待心情，因為世界上正式面世的只有一架處於研究狀態的前掠翼戰鬥機樣機，俄羅斯的Su-47( 先前稱 S-37 為 Berkut 或金雕) 戰鬥機。

美國和前蘇聯在第二次世界大戰時期，非常重視對納粹德國的軍工技術和科技研究人員的搶佔工作，德國的許多科學家紛紛去美國，而前蘇聯搜集運回國內大量的德國武器資料和樣品。從某種程度來看，其後美國和前蘇聯在一些科技發展領域是借鑒和繼續進行這些已有的成果。第二次世界大戰末期，前掠翼飛機在當時納粹德國科學家的理論和實踐研發中獲得初步發展，製造了採用15°前掠角的「容克－２８７」噴氣式轟炸機，該機於1944年2月進行了首次飛行，最大速度達到815公里／小時。前蘇聯繳獲了兩架樣機運回國內研究。７０年代中期以後，美、蘇兩國開始進一步研究前掠翼結構飛機。據有關資料，前掠翼根本性的難題是氣動發散：迎角和升力增大，造成機翼扭轉變形，前緣提高而後緣降低，迎角增大，機翼升力和扭轉變形進一步增大。在機體結構設計上，前掠角越大，氣動彈性發散現象越嚴重；當時只有加強機翼結構剛度來解決，同時造成飛機重量增加，抵消了前掠翼的優越性。

作者: 克里斯Chris 時間: 07-5-16 17:38
美國Ｘ－２９Ａ小型驗證機（Grumman X－29 A FSW）

雖然試飛成功，但技術難題未能完全解決。

美國在１９８２年由國防部高級項目管理處（ＤＡＲＰＡ）、美國空軍、美國國家宇航局（ＮＡＳＡ）共同投入資金研製小型前掠翼驗證機Ｘ－２９Ａ。１９８４年１２月２４日在美國加利佛尼亞愛德華空軍基地完成首次飛行，在１９８５年１２月１３日成功完成了前掠翼飛機的世界上首次超音速飛行。但這只是一種小型驗證機（只有普通戰鬥機的一半尺寸），由格魯曼公司設計製造，為降低造價，該機在結構上採用了不少生產型飛機的現成設備和組件，F—5A飛機的機頭和前起落架，F—16飛機上的主起落架等。機翼前掠角35度，為了改善前掠翼結構固有的高度不穩定空氣動力學外形特性，採用鴨翼設計，在前端增加兩個能控制滑動和扭轉的短翼（鴨翼），使整體具有良好的氣動性能，具有敏捷的操作性能，沒有水平尾翼。由於當時的世界綜合技術水平的局限，還是未能成功解決氣動發散難題，美國第四代戰鬥機的設計方案沒有採用前掠翼結構。

美國前掠翼驗證機Ｘ－２９Ａ相關數據：駕駛員人數一名；機長１４。６３米；機高４。２７米；翼展８。３２米；機翼面積１７。４平方米；最大速度１。６馬赫；最高昇限１５。３００米；使用美國普惠公司General Electric F404-GE-400渦扇發動機，最大推力71,17 kN，功率７１２０kp；空重６２６０kg，最大重量８０７４kg；有效負載１８１８kg。

美國目前只有兩架樣機。在１９８４－１９９２年期間，2架X-29A前掠翼試驗飛機進行了約442次試驗飛行，１９９４年退役後送到博物館展示。

美國在研製開發Ｘ－２９Ａ小型驗證機時採取了許多技術嘗試工作，採用復合材料的機翼和機體；數字電傳飛行控制系統；高推重比發動機；改進型機體設計，在設計上採用一對前置鴨翼來改進氣動性、改善操縱性能，而且這一設計被後來的俄羅斯Ｓ－３７殲擊機引用；美國Ｘ－２９Ａ小型驗證機使前掠翼戰鬥機方面研究又前進一步。

作者: Hiroster 時間: 07-5-17 01:20
前掠翼的優點在於低速機動跟纏鬥性吧

不過某兵器圖鑑也說過現今至未來視距戰為主流的時代中前掠翼的實用性備受考驗

S32未能受重視不就也是因為這樣嗎w?

而且西方大國都較偏向F\A-22跟艦載的F-35 歐洲偏向三角前翼小型戰機

只有蘇聯有符合今後水準的S32出現

這種型態的飛機說不定不太會趨於實用化?

以上一點拙見w

作者: 克里斯Chris 時間: 07-5-17 20:19

原文由Hiroster 於 07-5-17 01:20 AM 發表
前掠翼的優點在於低速機動跟纏鬥性吧

不過某兵器圖鑑也說過現今至未來視距戰為主流的時代中前掠翼的實用性備受考驗

S32未能受重視不就也是因為這樣嗎w?

而且西方大國都較偏向F\A-22跟艦載的F-35 歐洲偏向三角前翼小型戰機

只有蘇聯有符合今後水準的S32出現

這種型態的飛機說不定不太會趨於實用化?

嗯，前掠翼飛機在大迎角時首先從翼根部分開始失速，對飛機縱向﹑橫向的平衡和操縱都沒有影響，

失速特性比起後掠翼飛機來的好。讓前掠翼飛機低速性更好﹐可利用的升力比較大。

(維基百科，自由的百科全書資料)
前掠翼(swept-forward wing)與後掠翼相比(swept-back wing)，具備了一些優勢：

更高的升阻比(lift to drag ratio)
更高的纏鬥操控能力
次音速時更高的航程(range)
改良過的抗失速和反尾旋(anti-spin)特性
改良過的高攻角穩定度
更低的最小空速
更短的起降距離。

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視距戰是其中一項原因，而超視距戰已經成為世界先進戰機的制勝重點。

未來空戰特性還有很多因素，匿蹤技術、超音速等技術的廣泛應用，外國許多作戰飛機將裝備殺傷力更強的新型空對空導彈，並配備先進的雷達系統

從而使新一代作戰飛機能在更大的超視距範圍內精確地識別目標並進行精確打擊，這些作戰飛機與戰數數據鏈相聯接，數架戰鬥

機能共享戰數情報，從而使傳統的空軍單機和編隊戰數發生根本性變革。

而新一代戰機要求的重要隱身能力和超音速巡航能力，也造成不少戰機難逃被淘汰的命運。

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前掠翼最大的問題是在結構方面，沿結構曲線方向的彎曲變形會使外翼沿氣流方向增大迎角﹐增加外翼部分升力﹐進一步增加機翼的彎曲變形。速度太快，會造成機翼彎曲折斷，這現象稱彎扭發散(離散效應)。

因此只有把機翼結構重量的增加，但相對的，卻完全抵消採用前掠翼帶來的好處，造成前掠翼飛機很少被採用的主要原因。

但在70年代以後，有了新的技術；採用複合材料，讓前掠翼飛機又受到注目。

說到前掠翼歷史，最早的構想就是二戰時德國人應用在Ju-287上的技術。

-------

基本上習慣用Su-47來稱呼("金雕" Su-47戰鬥機)，S-32是Su-47舊稱。

-----

S-47是實用性最高的前掠翼飛機，也是最主要的前掠翼代表作。

----

前掠翼技術當然還是以俄羅斯最為先進，對美國來說，前掠翼實用性不高，

可變翼、三角前翼等反而合乎需求。

當然前掠翼戰機若擁有適合未來空戰的性質，實用化也不是不可能。

[ 本文最後由 jacklf2004 於 07-5-17 08:22 PM 編輯 ]

作者: 克里斯Chris 時間: 07-5-17 22:44
另外說明一下何為"失速"

失速

一般來說，飛機(機翼)的升力是與迎角(攻角)成正比的，迎角增加，升力隨之增大(圖1、圖2)。但是，一但迎角增大到某一值時，則會出現相反的情況，即迎角增加升力反而急劇下降。這個迎角就稱為臨界迎角。當飛機機翼迎角超過臨界點時，流經上翼面的氣流會出現嚴重分離，形成大量渦流，升力大幅下降，阻力急劇增加，飛機減速並抖動，各操縱面傳到桿、舵上的外力變輕，隨後飛機下墜，機頭下俯，這就是失速。

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