2018/4/27 Typical V-n Graph 国上清大孝 Load factors for various aircraft types 国上茶大坐 No Aireraft type Maximum positive load Maximam negative load factor Factor 25-38 -10-l5 Utiliy (semi- 44 -18 acrobatic Acrobatic 6 3 Homebuilt 5 6 3-4 110-2 Highly mancuverable 6.5-12 3o6 10614015180200220 DICATED AIL5光EDMH 2-4 -102 Biy-L Wenbin Song Some useful terminology 国上活大学 Structural Load -Distribution 圈上游大学 在结构设计中采钠的我药通常高于使用中 发生破坏所承受的最大我荷成为设计我荷， Aerodynamie Loads ·安全系数(snfety factor),了，设计我荷与使用载福的比值，所以设计我荷 可以由使用致有梨以安全东数得到，安全杀数基高，绍构设计所需段阔足 的载荷就越大，一般就意味着结构重量越大，在民机适航规范中，安全系 数取值为1.51 过我系数(imit load factor)小，飞机承受的除重力外的所有外力之和与重力 之比，称为该方向上的过载： 在飞机完成飞行任务的整个过程中，作用在飞机上的载荷是多种多样的，主 要可以分为两大类，债性我荷和气动玻黄。结构强度设计通常按照设计我荷来 进行，同时还受到飞机种类的区别，对与战斗机而言，飞过载的选取还要 考感飞行员能第承受的最大过。 一般选取n<9 Evolution of Design Requirements 图上承大峰 JAR 25.571 evaluation related to fail safety and damage tolerance 国上游毛大堂 time Design requirements Linked accidents Amendment Summary of changes 19505 Adequate limit and ultimate strength level(date) 1950s Design for fatigue performance and fail Comet sccident 24-0 d Falu'e 2401954 1978 Damage tolerance requirements Boeing 707 stabilizer fadure w19g0 Fu e testing to pred 25-45 sse-tolerance e-tolaranc (fa fatigue damage(WFD) 1Dec.1978 FAR or JAR (Joint Aviation Regulation)25-571 has evolved over the years n of and Influence pro foundly the airframe tructur sign today (http://www.jaa.nl) 25-96 Damage-tolerance (30Apra1998) and fatizue evaluation of structures for WFD2018/4/27 3 © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics Typical V-n Graph http://avstop.com/ac/flighttrainghandbook/vgdiagram.html © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics Load factors for various aircraft types © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics Some useful terminology © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics Structural Load - Distribution Aerodynamic Loads © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics Evolution of Design Requirements 17 time Design requirements Linked accidents ~1950s Adequate limit and ultimate strength 1950s Design for fatigue performance and fail safety Comet accident 1978 Damage tolerance requirements Boeing 707 stabilizer failure ~1980 Full scale fatigue testing to preclude widespread fatigue damage (WFD) Aloha 737 fuselage incident FAR or JAR (Joint Aviation Regulation) 25.571 has evolved over the years and Influence profoundly the airframe design today (http://www.jaa.nl) © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics JAR 25.571 evaluation related to fail safety and damage tolerance 18 Amendment level (date) Title Summary of changes 24-0 (24 Dec. 1964) Fatigue evaluation of flight structure (c) Fail safe strength. “It must be shown by analysis, tests, or both that catastrophic failure or excessive deformation, that could adversely affect the flight characteristics of the airplane, are not probable after fatigue or obvious partial failure of a sing principle structural element (PSE).” 25-45 (1 Dec. 1978) Damage-tolerance and fatigue evaluation of structure (b) Damage-tolerance (fail-safe) evaluation. “The evaluation must include a determination of the probable locations and modes of damage due to fatigue, corrosion, or accidental damage. The residual strength evaluation must shown that the remaining structure is able to withstand loads corresponding to …” 25-96 (30 April 1998) Damage-tolerance and fatigue evaluation of structures for WFD (b) Damage-tolerance evaluation, for WFD. Initial flaw of maximum probable size from manufacturing defect or service induced damage used to set inspection thresholds; sufficient full-scale fatigue test evidence must demonstrate that WFD will not occur within DSO(no airplane may be operated beyond cycles equal to one-half the cycles on fatigue test article until testing is completed)