Airframe Handbook.pdf - AC65-15A Airframe Or Powerplant...

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Unformatted text preview: AC65-15A Airframe Or Powerplant MECHANICS AIRFRAME HANDBOOK U.S. DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION ADMINISTRATION AIRFRAME A N D POWERPLANT MECHANICS AIRFRAME H A N D B O O K US. DEPARTMENT O F TRANSPORTATION FEDERAL AVlATiON ADMINISTRATION FLIGHT STANDARDS SERVICE First Edition 1972 First Revision 1976 PREFACE This handbook was developed and first printed in 1972 as one of a series of three handbooks for persons preparing for certification as an airframe or powerplant mechanic. It is intended that this handbook will provide basic information on principles, furdamentals and technical procedures in the subject matter areas relating to the airframe rating. It is designed to aid students enrolled in a formal course of instruction as well as the individual who is studying on his own. Since the knowledge requirements for the airframe and powerplant ratings closely parallel each other in some subject areas, the chapters which discuss fire protection systems and electrical systems contain some material which is also duplicated in the Airframe and Powerplant Mechanics Powerplant Handbook, AC 65-12A. This volume contains information on airframe construction features assembly and rigging, fabric covering, structural repairs, and aircraft welding. The handhook also contains an explanation of the units which make up the various airframe systems. Because there are so many different types of aircraft in use today, it is reasonable to expect that differences exist in airframe components and systems. To avoid undue repetition, the practice of using representative systems and units is carried out throughout the handbook. Subject matter treatment is from a generalized point of view. and should be supplemented by reference to manufacturers' manuals or other textbooks if more detail is desired. This handbook is not intended to replace, substitute for, or supersede official regulations or the manufacturers' instructions. Grateful acknowledgement is extended to the manufacturers of engines. propellers and powerplant accessories for their cooperation in making material available for inclusion in this handbook. Copyright material is used by special permission of the following organizations and may not be extracted or reproduced without permission of the copyright owner. Monsanto Chemicals Co. Townsend Corporation J. 0. King, Inc. Gravines, Inc. Walter Kidde DuPont De Nemours National Fire Protection Association National Association of Fire Extinguisher Distributors Flight Safety Foundation 4merican Petroleum Institute Exxon Corporation Parker Hannifin Goodyear Tire and Rubber Co. Firestone (R) Skydrol CE3 Fluids Cherry Rivets Acres Sleeves Acres Sleeves Fire Extinguishers Fire Extinguishen Fire Extinguishants Fire Extinguisher and Extinguishant Specifications Fire Extinguishers Refueling Data Aviation Fuels Aviation Fuels Aircraft Fittings Aircraft Tires Aircraft Wheels Aircraft Brakes Aircraft Tires Bendix Energy Controls Aircraft Wheels Aircraft Brakes Plastics Portable Oxygen Generators in the D C l O Air Conditioning Aircraft Tires Aircraft Wheels Aircraft Brakes Portable Oxygen Generators Rohm and Haas Douglas Aircraft Company Aviation Maintenance Foundation, Inc. BF Goodrich Puritan Equipment, Inc. The advancements in aeronautical technology dictate that an instructional handbook must be under continuous review and brought up to date periodically to be valid. Flight Standards requested comments, from the certificated mechanic schools on the three handbooks. As a result, the handbooks have been updated to this extent: indicated errors have been corrected, new material has been added in the areas which were indicated as being deficient, and some material has becia rearranged to improve the usefulness of the handbooks. We would appreciate having errors brought to our attention, as well as receiving suggestions for improving the usefulness of the handbooks. Your comments and suggestions will be retained in our files until such time as the next revision will be accomplished. Address all correspondence relating to these handbooks to: US. Department of Transportation Federal Aviation Administration Flight Standards National Field Office P.O. Box 25082 Oklahoma City, Oklahoma 73125 The companion handbooks to AC 65-15A are the Airframe and Powerplant Mechanics General Handbook, AC 65-9A and the Airframe and Powerplant Me. chanics Powerplant Handbook, AC 65-12A. iv CONTENTS PREFACE _________.______________________________---------------- iii CONTENTS - _____ -__- _____ - _________ -__-__- ________________ - _____ - ” CHAPTER 1. AIRCRAFT STRUCTURES G eneral ___-_-__-__--__-__-_____________________--------------Major Structural Stresses ________________________________________ Fixed-Wing Aircraft ________________________________________---Fuselage ________________._______________________-------------Wing Structure _____._________________________________ L ________ Nacelles or Pods ______________._________________________------Empennage ________________________________________-----------Flight Control Surfaces ________________________________________-Landing Gear ________-_______________________________---------Skin and Fairing __-__-_________-________________________------Access and Inspectmn Doors ______ - _________________ - _____ -___-__ Helicopter Structures _-- _____ -__-__-__-- ___________ -__-___-__-___ 1 1 2 2 6 13 16 18 23 24 24 24 CHAPTER 2. ASSEMBLY AND RIGGING General -__-__-__-______-__-____________________--------------Theory of Flight _--__-__-_________-_____________________------Aerodynamics ________________________________________---------The Atmosphere ________________________________________-------Pressure -__-__-__-______-__-____________________-------------Density -__-__-__--__-__-__-____________________-----~---~----Humidity., ________________________________________------------. . Bernoulb s Prmc~ple and Subsomc Flow ____________________________ Motion _-.___________-_________________________--------------A’*r f 01s ‘I __-_________-__-__-_----------------------------------Center of Gravity ___- ________________________________________--Thrust and Drag ________________________________________------Axes of an Ancraft ________________________________________----Stability and Control -__- _________ -__- ___________________________ Control _-______-__-__-__-______________________--------------Flight Control Surfaces -__--__- ______ -__- ______ -__- ______________ Control Around the Longitudinal Axis _-__- ______ - _________________ Control Around the Vertical Axis _-- _________ - ____________________ Control Around the Lateral Axis ______ -__-___- _____ - ______________ Tabs __._____________________________________----------------Boundary Layer Control Devices’ __________________________________ Forces Acting on a Helicopter __-__- ______________________________ Helicopter Axes of Flight ________________________________________ High-Speed Aend ynamics .______________________________________ Typical Supersonic, Flow Patterns ______ -__-__- _________ - __________ Aerodynamic Heating __-__--__-__-__- _______________ -- __________ Flight Control Systems ________________________________________-Hydraulic Operated Control Systems ______________________________ Cable Guides ________________________________________---------Mechanical Linkage ________________________________________---- 27 27 27 27 27 28 28 29 29 30 33 33 35 35 39 40 41 z 45 48 49 55 56 59 64 64 65 66 68 68 68 69 70 72 75 77 80 83 83 85 88 89 91 93 95 95 99 103 104 104 106 106 107 107 108 109 109 109 110 111 113 113 117 117 117 118 118 119 120 121 121 122 122 123 vi CHAPTER 4. AIRCRAFT PAINTING AND FINISHING-(Cont.) 124 125 125 127 129 130 131 131 133 136 141 145 146 148 151 155 164 166 168 173 175 177 177 178 181 184 184 186 187 187 189 198 200 201 201 202 205 206 208 209 213 213 214 215 220 221 221 223 224 224 228 230 232 234 235 242 24d 245 247 248 255 255 257 258 258 260 262 263 264 265 266 269 276 285 286 287 288 291 293 296 299 300 303 303 308 309 309 310 311 313 315 316 323 328 329 331 334 338 341 348 351 351 354 356 360 366 372 373 377 379 381 382 384 385 389 390 391 392 394 396 396 397 399 400 407 408 411 412 412 417 417 419 420 422 423 425 425 429 429 430 ... ~~ 433 444 446 450 451 452 452 457 457 459 46% I. ,... %9 469 469 470 470 471 471 474 481 482 483 485 485 487 488 491 491 497 497 4w 501 [email protected] 506 506 507 511 51 3 519 519 520 522 522 524 524 525 528 529 530 530 531 532 533 533 534 536 537 539 539 541 543 545 545 549 550 551 556 558 559 561 564 565 565 568 574 575 576 577 580 583 585 586 587 587 588 588 589 591 592 594 597 597 597 598 600 . xi . CHAPTER 1 AIRCRAFT STRUCTURES GENERAL The airframe of a fixed-wing aircraft is generally considered to consist of five principal units, the fuselage, wings, stabilizers, fight control surfaces, and landing gear. Helicopter airframes consist of the fuselage, main rotor and related gearbox, tail rotor (on helicopters with a single main rotor), and the landing gear. The airframe components are constructed from a wide variety of materials and are joined by rivets, bolts, screws, and welding or adhesives. The air. craft components are composed of various parts called structural members (;.e., stringers, longerons, ribs, bulkheads, etc.). Aircraft structural members are designed to carry a load or to resist stress. A single member of the structure may be subjected to a combination of stresses. In most c a m the struo tural members are designed to carry end loads rather than side loads: that is, to be subjected to tension or compression rather than bending. Strength may be the principal requirement in Certain structures, while others need entirely different qualities. For example, cowling, fairing, and similar parts usually are not required to carry the stresses imposed by flight or the landing loads. However, these parts must have such properties as neat appearance and streamlined shapes. (1) Tension. (2) Compression. (3) Torsion. (4) Shear. ( 5 ) Bending. The term “stress” is o h used intemhangeably with the word “strain.” Stress is an internal force of a substance which oppow or resists deformation. Strain is the deformation of a material or substance. Stress, the internal force, can cause Strali. Tension (figure 1-la) is the stress that resists a force that tends to pull apart. The engine pulls the aircraft forward, but air resistance tries to hold it back. The result is tension, which tries to stretch the aircraft. The tensile strength of a material is measured in p.s.i. (pounds per square inch) and is calculated by dividing the load (in pounds) required to puil the material apart by its croea-8dctional area (in square inches). Compression (figure I-lb) is the stress that re5 ists a crushing force. The compressive strength of a material is also measured in p.8.i. Compression is the stress that tends to shorten or squeze aireraft P-. Torsion is the stress that produces twisting (figure 1-lc). While moving the aircraft forward, the engine also tends to twist it to one side, but other aircraft components bold it on course. Thus, torsion is created. The torsional strength of a material is iia resistance to twisting or torque. Shear is the stress that resists the force tendmg to cause one layer of a material to slide over an adjacent layer. Two riveted plates in tension (figure 1-Id) subject the riveta to a shearing force. Usually, the shearing strengtb of a material is either equal to or lesa than its tens& or compressive strength. Aircraft parts, especially screws, bolts, and rivets, are often subject to a shearing force. Bending stress is a combination of compression and tension. The rod in figure I-le has been shortened (comprawred) on the inside of the bend and stretched on the outside of the bend. MAJOR STRUCTURAL STRESSES In designing an aircraft, every square inch of wing and fuselage, every rib, spar, and even each metal fitting must be considered in relation to the physical characteristiui of the metal of which it is made. Every part of the aircraft must be planned to carry the load to be imposed upon it. The determination of such loa& is cailed stress analysis. Although planning the design is not the function of the aviation mechanic, it is, nevertheless, important that he understand and appreciate the stresees involved in order to avoid changes in the original design through improper repairs. There are five major strcsses to which ail aircraft are subjected (figure 1-1) : 1 l P 0 fc) Torsiod (e) FIGURE 1-1. Banding (the c5ubhuöon S t W Y ) Five atrasses acting on an aircrah. FIXED-WING AIRCRAFT The principal components of a single-engine, propeller-driven aircraft are shown in figure 1-2. Figure 1-3 illustrates the structural Components of a typical turbine powered aircraft. One wing and the empennage assemblies are shown exploded into the many components which, when assembled, form major structural units. multi-engine aircraft the engines may either be in the fuselage, attached to the fuselage, or suspended from the wing structure. They vary principally in &e and arrangement of the different compartments. There are two general types of fuselage constmction, the truss type, and the monocoque type. A truss is a rigid framework made up of members such as beams, struts, and bars to resist deformation by applied loads. The truss-framed fuselage is generally covered with fabric. FUSELAGE The fuselage ia the main structure or body of the aircrait. It provides space for cargo, controls, accessories, passengers, and other equipment In singleengine aircraft, it also houses the powerplant. In Truss Type The truss type fuselage frame (figure 1-4) is usually constructed of steel tubing welded together in such a manner that all members of the tmas can carry both tension and compression loads. In some 2 Frcoul-E Ainmftarontrralwmponcma In addition to formem, frame assemblieu, and bulkheads, the semimonocoque construction has the skin reinforced by longitudinal memhera. The reinforced shell bae the skin reinforced by a compi.te framework of structural members. Different pop tions of the same fuselage may belong to my one of the three classee, but moot aircraft are considered to be of semimonocope type consmc~on. aircraft, principally the light, singloengine mod& trues fuselage frames are constructed of alminum d o y and may be riveted or bolted into one piece, with cross-bracing achieved by using solid rods or tubes. Monocoque Type The monocoque (single shell) fuaelsge relies largely on the strength of the skin or covering to carry the primary stresses. The design may be divided into three cineses: (1) Monocoque, (2) semi. monocoque, or (3) reinforced shell. The true monoformers, coque construction (figure 1-5) frame assemblies, and bulkheads to give shape to the fuselage, but the &in cania, the primary stresses. Since no bracing memhera are preseia, the skin mnst be strong enongh to keep the W a g e rigid. Thus, the biggest problem involved in monocoque construction is maintaining enough strength while keeping the weight within allowable limits. To overcome the strength/weight problan of monocoque construction, a modification Caned semimonocoque construction (figure 1-6) was deveiOped SemimonOcWJe TYPe The eemimonocoque W a g e is constructed psmarily of the d o y s of aluminum and magn&~m, although steel and titanium are found in areas of high tsmperatuies. Primary bending loads are taken by the bngerom, which usually extend acroen emerd points of support The longuons are supple mented by other longitudinal membels, called stringers. Stringers are more nUmCIOüü and lighter in weight than longerons. The vertical structnral memhera ere referred to ae bulkheads, h n < and , formers. The heaviest of theae vertical d e m are located at intervals to carry concentrated loads and at points where fittings are used to attach other units, such as the win& powerphts, and stabilis. 3 Wing center section or. strut edge Powerplant FIGURE 1-3, Typid anicturai mmponuita of a turbine powered eimdt, Longeron (tnbular steel) rons and serve as fin-ins. They have some rigidity, but are chiefly used for giving shape and for attachment of the skin. The strong, heavy longerons hold the bulkheads and formers, and these, in turn, hold the stringers. All of these joined together form a rigid fuselage framework. There is often little differenee between some rings, frames, and formers. One manufacturer may call a brace a former, whereas another may call the same type of brace a ring or frame. Manufacturers’ instructions and specifications for a specific aircraft are the best guides. Stringers and longerons prevent tension and compression from bending &e fuselage. Stringers are usually of a one-piece aluminum alloy coiistruction, and are manufactured in a variety of shapes by casiing, extrusion, or forming. Longerons, like stringers, are usually made of aluminum alloy; how- Diagonal web members (tubuiar steei) hcvag 1 4 W m m irues of welded tub& steel e m Figure 1-7 shows one form of the semimonocoque design now in use. The stringers are smaller and lighter than longe4 . . . ..>.- , . . 1 _ . o . . . . ...,, ,.----- :7 , . ~ I ’.,. doea not depend on a few members for strength and rigidity. ”his means that a ssmimonocoque fiwelnge, because of its stressed-skin construction, may withstand considerable damage and stili be shong enough to bold together. Fuselages are generaily constructed in two or more sections. On small aircraft, they are p e r a l l y made in two or three sections, while larger aircraft may be made up of aa many aa six d o n s . Quick a m to the accessories and other equip ment carried in the fuselage is provided for by numerous acceaa doom, inspection platea, landing wheel wells, and other openings. Servicing diagrams showing the arrangement of equipment and loeation of a m doom are supplied by the manufachurr in the aircraft maintenance manual. ever, they may be of either a one-piece or a built-up construction. By themselves, the structural members discussed do not give strength to a fuselage. They must first be joined together by such connective devicea aa g-, [email protected] nuts and bolts, or metal screws. A gusset (figure 1-7) is a type of connecting bracket. The bracing between longerons is often referred to as web members. They may be installed verticaily or diagonaily. The metal sün or covering is riveted to the longerons, buikhads, and other structural membera and carries part of the load. The fusdage skin thicknees wiii vary with the load carried and the stresses sustained at a particular location. There are a number of advantages in the use of the semimonocoque fuselage. The bulkhads, frameu, stringers, and longerons facilitate the d e sign and construction of a stnamüned fuselage, and add to the strength and rigidity of the structure. The main advantage, however, iim in the fact that it Loca?ionNumbering Systems There are various numbering systems in ww to facilitate location of specific wing frames fuselegs bulkheads, or any other structural m&rs on an aircraft. Most manufacturers use some s w of station marking; for example, the no88 of the allcraft may be designated zero station, and all other stations are located at measured ditanoes in inchss behiid the zero station. Thns, when a blueprint reads “fuselage frame station 137,” that p d & frame station can be located 137 in. behmd the no88 of the aircraft. A typical station diagram is shown in figure 1-8. To locate structured to the right or left of the center line of an aircraft, many manufachinrs consider the center iine as a zero station for stniehuil member location to its right or I& With such a 5 dicuiar to the rear beam of the wing and parsllel to, and outboard from, the inboard edge of the flap. ( 6 ) Nacelle siation (N.C. or Nac. Sui.) ie measured either forward of or bebind the front spar of the wing and perpeudicular to a designated water line. In addition...
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