【正文】 nt analysis, simulation the stress of the landing gear in the real situation, estimated the failure, loading of the important parts such as hydraulic ponents. It plays a vital significance to fault prediction of aircraft structure. The history of CATIA CATIA started as an inhouse development in 1977 by French aircraft manufacturer Avions Marcel Dassault, at that time customer of the CAD/CAM CAD software to develop Dassault39。 然后介紹 了下 CATIA V5 的特點、應(yīng)用 、 基本操作 、 各種工作界面 、零部件設(shè)計、裝配設(shè)計、運(yùn)動仿真、 及較高層次的應(yīng)用。然后將各個部件導(dǎo)入裝配設(shè)計工作臺，進(jìn)行組裝 ，添加結(jié)構(gòu)約束 。s Kitten, built in 1917, had retractable gear (but could not actually fly). The Dayton Wright RB1(Figure 21) of 1920 and the Verville Sperry R3 of 1922 also had retractable gear. But these aircraft were rarities and most airplanes had fixed landing gear at the end of metal struts because they 中國民航飛行學(xué)院航空工程學(xué)院畢業(yè)論文 5 were easy to design, strong, and relatively lightweight. Figure 21 Aircraft RB1 When designing an aircraft, engineers have always had to address five conflicting requirements. These are: performance, weight, cost, reliability, and maintenance. The best solution to the performance requirement was to pull the landing gear pletely inside the fuselage and cover them over, presenting a smooth surface that produced no drag. But while ideal from a performance standpoint, this approach affected all of the other requirements at weighed more, cost more, was less reliable, and required more mai ntenance. The wind tunnel data from the PRT caused aircraft designers to look immediately for ways of developing landing gear that provided better performance and hopefully did not have too many other costs associated with them. The Boeing Monomail, which first appeared in 1930, and the Lockheed Orion are generally considered pioneers in the development of retractable landing gear, proving that it was practical. But airplane designer Jack Northrop, who was very interested in streamlining aircraft to improve performance, produced the Northrop Alpha, Beta, and Gamma with fixed landing gear during the 1930s. These aircraft had streamlined coverings that extended down from the fuselage, with the wheels sticking out at the bottom. These were generally referred to as trouser gear. (Figure 22) The Lockheed Sirius, which was built for Charles Lindbergh, had streamlined coverings over the wheels themselves that were referred to as pantstype landing gear. Although trouser and pants gear produced more drag than fully retracted gear, they were still a substantial improvement over uncovered landing gear. More importantly, they were still lighter, cheaper, more reliable, and easier to maintain than the retractable gear. But during the 1930s, numerous designers embraced retractable gear hey were willing to accept the other drawbacks of retractable landing gear 基于 CATIA 的 大型飛機(jī)起落架建模與分析 6 simply to achieve the better performance. Figure 22 Pantstype landing gear Airplane designers explored numerous ways to retract aircraft landing gear into the fuselage. In some aircraft they were pulled straight up, usually into cowlings behind the engines, sometimes with part of the wheels protruding outside the airplane. In other cases, particularly with smaller aircraft, the struts folded inward so that the wheels fit into the bottom of the fuselage horizontally, sometimes covered with a door to further reduce drag. Some of the drive mechanisms were electric, whereas others were hydraulic. The designers had to ensure that the gear deployed and locked in place. Landing gear that collapsed when a plane landed could cause the plane to tumble out of control and kill the pilot, or at least seriously damage the airplane. For early retractable landing gear not even the performance improvements were clearly achievable, since a retractable landing gear with its motors and associated machinery weighed more than a fixed gear, thereby requiring greater lift from the aircraft and negating some of the benefits of the reduced drag of the retracted gear. While retracting the gear could improve the performance of the plane, it might require a bigger engine and more fuel not to mention more money. In fact, it was this delicate tugofwar between the extra weight of the gear and the reduced drag that was most important for the overall acceptance of retractable landing gear. Drag increases with speed and therefore reducing drag bees more important as an aircraft39。 the aircraft then relies 基于 CATIA 的 大型飛機(jī)起落架建模與分析 10 on titanium skids on the wingtips for landing Figure 26 Takeoff dolly Figure 27 Aircraft U2 Some main gear struts on World War II aircraft, in order to allow a singleleg main gear to more efficiently store the wheel within either the wing or an engine nacelle, rotated the single gear strut through a 90176。s shock absorption was taken up by a vertically sliding bungee cordsprung upper member. The vertical post along which the upper member slid to take landing shocks also had its lower end as the rotation point for the forward end of the main wheel39。s nose in the down position for better ground handling, with a retracted position that placed the main wheels at some angle behind the main 中國民航飛行學(xué)院航空工程學(xué)院畢業(yè)論文 11 gear39。39。在本文的最后， 總結(jié)各種不足和待改進(jìn)之處 ， 并且對 CATIA 建模的 優(yōu)缺 點進(jìn)行總結(jié)及展望 。分類號 V22 編 號 U D C 621TH12 密 級 公 開 中國民航飛行學(xué)院 畢業(yè)設(shè)計（論文） 題 目 基于 CATIA 的大型飛機(jī)起落架建模與分析 The mercial aircraft landing gear modeling and analysis based on CATIA 作者姓名 專業(yè)名稱 熱能與動力工程 指導(dǎo)教師姓名及職稱 提交日期 2020 年 6 月 12 日