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1、SUBCOURSEEDITION AL0992A BASIC AIRFRAME REPAIR BASIC AIRFRAME REPAIR Subcourse Number AL0992 EDITION A US Army Aviation Logistics School Fort Eustis, Virginia 23604-5439 4 Credit Hours Edition Date: September 1994 SUBCOURSE OVERVIEW This subcourse is designed to provide you with a general familiariz
2、ation of the airframe of todays aircraft and repair procedures. You will study the design and construction of aircraft parts and assemblies, metals used in the construction, and the metal qualities and stresses involved. You will also study procedures involved in the repair of damages to the aircraf
3、t skin and structure and the type of hardware required. Early aviations aircraft made of wood and fabric, reinforced with metal, were strong enough to withstand the vibrations and torsion stresses met at slow speed. However, with the need for higher speeds, greater payloads, and more powerful engine
4、s, wood became unsatisfactory. Manufacturers and designers realized that structural parts made with metal must replace the wood and fabric. So they developed light, strong metal alloys. To these they applied structural forming and reinforcing methods to reduce weight and to gain the strength require
5、d for increased performance. Making repairs involved selecting the right metal for structural strength and streamlining, choosing the type of rivet to use, and determining the type of patch that will meet structural requirements. Also important is determining how much weight can be added, within saf
6、e limits, and choosing the method of structural forming and reinforcement to use. You will find this text divided into two chapters which discuss airframe parts, metals, processes, hardware and damage repair. However, the discussion here is not a substitute for the technical manual (TM) applicable t
7、o a specific aircraft or a particular repair technique. The information given here is designed to give you a general background in basic airframe repair. iAL0992 This subcourse is to be completed on a self-study basis. You will grade your lessons as you complete them using the lesson answer keys whi
8、ch are enclosed. If you have answered any question incorrectly, study the question reference shown on the answer key and evaluate all possible solutions. There are no prerequisites for this subcourse. This subcourse reflects the doctrine which was current at the time it was prepared. In your own wor
9、k situation, always refer to the latest publications. Unless otherwise stated, the masculine gender of singular pronouns is used to refer to both men and women. TERMINAL LEARNING OBJECTIVE ACTION:You will demonstrate a knowledge of the basic fundamentals of airframe repair including airframe parts,
10、metals, metal processing, hardware, and required procedures. CONDITIONS:You will use the material in this subcourse. STANDARD:To demonstrate competency of this task, you must achieve a minimum of 70% on the subcourse examination. iiAL0992 TABLE OF CONTENTS SectionPage Subcourse Overviewi Administrat
11、ive Instructions.iv Grading and Certification Instructionsiv Lesson 1: Airframe Parts, Metals, Processes and Hardware1 Part A:Airframe Parts.2 Part B:Metal Qualities and Stresses.16 Part C:Metal-Working Processes20 Part D:Aviation Hardware28 Practice Exercise.41 Answer Key and Feedback.44 Lesson 2:
12、Damage Repair.47 Part A:Principles of Repair.48 Part B:Structural Repair51 Part C:Stressed Skin Repairs60 Part D:Internal Structure Repair72 Part E:Structural Sealing.86 Practice Exercise.91 Answer Key and Feedback.94 Appendix: Glossary101 Student Inquiry Sheet iiiAL0992 LESSON 1 AIRFRAME PARTS, MET
13、ALS, PROCESSES, AND HARDWARE STP Tasks: 551-753-1002 551-753-1004 551-753-1010-1014 551-753-1020 551-753-1035 551-753-1068 552-753-3007 OVERVIEW LESSON DESCRIPTION: In this lesson you will learn airframe parts, metal qualities and stresses, metal working processes, and selected items of aircraft har
14、dware. LEARNING OBJECTIVE: ACTION:You will identify and describe airframe parts demonstrate your knowledge of aircraft metals and metal processing, and apply your knowledge of selected items of aircraft hardware. CONDITIONS:You will study the material in this lesson in a classroom environment or at
15、home. STANDARDS:You will correctly answer all the questions in the practice exercise before you proceed to the next lesson. REFERENCES:The material contained in this lesson was derived from the following publications: FM 1-563 (Fundamentals of Airframe Maintenance). TM 1-1500-204-23-10 INTRODUCTION
16、An aircraft is constructed of many parts, or structural members, that are either riveted, bolted, screwed, bonded, or welded together. These structural members form units or assemblies, and they are then designated principal airframe parts. Individual structural members may vary in size, shape, or c
17、omposition; however, the principal airframe parts they form are readily identified on any conventional aircraft as illustrated in Figures 1-1 and 1-2. 1AL0992 Figure 1-1. Principal Airframe Parts (Airplane). Some aircraft manufacturers may use different names for the parts of an airplane or helicopt
18、er airframe, but the names shown in the figures are understood internationally. A working knowledge of the location, construction, and purpose of the various structural units of the aircraft is the basis for an intelligent approach to airframe repair. This chapter, divided into four sections, descri
19、bes airframe parts, metal qualities and stresses, metal-working processes, and aviation hardware. PART A: AIRFRAME PARTS GENERAL The principal parts of an airframe are most commonly made of aluminum alloys in the form of shells. As a result, the main 2AL0992 Figure 1-2. Principal Airframe Parts (Hel
20、icopter). problem is to make the relatively thin shells strong enough to withstand compression and shear loads and to maintain a favorable weight-to-strength relation. In general, the discussion here explains how this is achieved for airplanes and helicopters. This section describes the four princip
21、al parts of an airplane and the cabin and tailboom sections of a helicopter. The descriptions include details involving truss, monocoque, and semimonocoque constructions. PRINCIPAL AIRFRAME PARTS (AIRPLANES) An airplanes four principal parts are the fuselage, nacelle, wings and empennage. The descri
22、ptions in the following paragraphs cover the truss, monocoque, semimonocoque, and 3AL0992 reinforced shell constructions for the fuselage; the structural members used; construction for the nacelle; monospar, multispar, and box-beam wing constructions; and empennage constructions. Fuselage. The main
23、structural unit of an airplane is the fuselage. Other structural units are directly or indirectly attached to it. In outline and general design, the fuselage of one airplane is much the same as any other. Designs vary principally in the size and arrangement of the different compartments. On military
24、 single-engine airplanes, the fuselage houses the powerplant, personnel, and cargo. The basic fuselage constructions are truss and monocoque. The truss construction, a rigid framework of beams, struts, and bars, shown in Figure 1-3, resists deformation by applied loads. Many smaller general aviation
25、 aircraft and a number of older military aircraft have used truss construction. A monocoque fuselage, shown in Figure 1-3, is like a shell in that the skin bears the primary stresses in spite of the formers, frame assemblies, and bulkheads that give the fuselage its shape. The construction strength
26、required depends upon the power used, speed, maneuverability, and design. The full monocoque construction is seldom used because the skin is the principal part of the airframe. The big problem in monocoque construction is maintaining strength and keeping weight down. To overcome this problem, the se
27、mimonocoque and reinforced shells were developed. These shells are used in the majority of present-day military aircraft. Figure 1-3. Fuselage Construction. 4AL0992 The semimonocoque fuselage, in addition to having vertical reinforcements (formers), has the skin reinforced by longitudinal members (s
28、tringers and longerons). The reinforced shell has the skin reinforced by a complete framework of structural members. Examples of semimonocoque and reinforced shell constructions are shown in Figures 1-4 and 1-5. Figure 1-4. Semimonocoque Construction. Structural Members. Formers, frame assemblies, a
29、nd bulkheads give cross-sectional shape, rigidity, and strength to the fuselage. The shapes and sizes of these members vary considerably, depending on their function and position in the fuselage. Formers are the lightest, and they are used primarily for fillings or skin attachments between the large
30、r members. Frame assemblies are the most numerous and outstanding members 5AL0992 in the fuselage in appearance and as strengthening devices. Whenever frame assemblies are used to separate one area from another, they are circular or disc-shaped, reinforced, and equipped with doors or other means of
31、access, and are then called bulkheads. Channel members, hat-shaped sections, and built-up assemblies are inserted to give additional strength. Station webs are built-up assemblies located at various points to attach fittings or external parts, such as empennage surface fittings, engine mounts, wing
32、attachments, and landing gear. Figure 1-5. Reinforced Shell Construction. Stringers and longerons are the main lengthwise members in fuselage structures. Notice in Figure 1-5 that the longeron is a fairly heavy member. Usually, several of these run the whole length of the fuselage. The stringers are
33、 smaller and lighter, and are used primarily for giving shape to the attached skin. 6AL0992 Longerons are stronger and heavier than stringers, and hold the bulkheads and formers, which, in turn hold the stringers. All these joined together make a rigid fuselage framework. Nacelle. The streamlined st
34、ructures (nacelles) on multiengine aircraft are used primarily to house engines. Figure 1-6 shows the construction of a nacelle in general use. Here also, designs vary depending upon the manufacturer and the use to be made of the nacelle. On twin-engine airplanes, nacelles also house the main landin
35、g gear and related equipment. Whether the nacelle houses a reciprocating piston or jet engine, Figure 1-6. Nacelle Construction. landing gear, or cargo, repair fundamentals are essentially the same as for a fuselage. The nacelle must have sufficient strength to withstand the compression and shear lo
36、ads it will be subjected to; its weight must be kept within allowable limits; and the exterior must be aerodynamically suited for the nacelles location on the aircraft. 7AL0992 Wings. Airplane surfaces designed to give lifting force when moved forward rapidly through the air are wings. Wing design f
37、or any given airplane depends upon size, weight, and use of the airplane; desired speed in flight and at landing; and the desired rate of climb. Wings are designated as left and right, corresponding to the left and right hands of the pilot seated in the cockpit. Variations in design give a wing its
38、particular features. The wing tip may be square, rounded, or tapered. Both the leading edge and the trailing edge of the wing may be straight or curved. Many types of modern airplanes have swept-back wings. Wings on military airplanes are generally of cantilever design; that is, no external bracing
39、is needed. Wings of this design are usually of the stressed-skin type. This means that the skin is part of the wing structure and carries part of the wing stresses. Spar and Box-Beam Wings. In general, monospar, multispar, and box- beam are the three basic wing-construction designs. Modifications of
40、 these designs may be used by various manufacturers. A separate description of each basic design is given in the paragraphs that follow. The monospar wing has only one main longitudinal member in its construction. Ribs or bulkheads supply the necessary contour or shape to the airfoil. The strict mon
41、ospar wing is not in common use. However, this design is modified by adding fake spars or light shear webs along the trailing edge to support the control surfaces. The multispar wing has more than one main longitudinal member in its construction. To give the wing contour and relieve stress on the wi
42、ngs skin, ribs or bulkheads are often included. This construction, or some modification of it, is used in lighter airplanes. The box-beam wing uses two main longitudinal members with connecting bulkheads to give additional strength and contour to the wing. A corrugated sheet of aluminum alloy may be
43、 placed between the bulkheads and the smooth outer skin so that the wing can better carry tension and compression loads. Sometimes, heavy longitudinal stiffeners are substituted for the corrugated sheets. A combination of corrugated sheets on the upper surface of the wing and stiffeners on the lower
44、 surface is sometimes used. Wing Spars. Figure 1-7 shows spars, ribs, bulkheads, stringers, and stiffeners. These, the wings main structural components, are riveted or welded together. 8AL0992 Figure 1-7. Wing Construction. 9AL0992 Spars are the principal structural members of the wing. They corresp
45、ond to the longerons of the fuselage. Spars run from the base of the wing toward the tip and are usually attached to the fuselage by wing fittings, plain beams, or part of a truss system. The I-beam construction for a spar consists of a web, a deep wall plate, and capstrips. These are either extrusi
46、ons or formed angles, as shown at Detail A in Figure 1-7. The web, the principal depth portion of the spar, is attached to the capstrips that carry the loads caused by the wings bending. When joined, the web and capstrips form a foundation for attaching the skin. Stiffeners give additional strength
47、to the spar structure. These may be beads pressed into the web or extrusions or formed angles riveted to the web vertically or diagonally. Wing Ribs. In the framework of a wing, ribs are the crosspieces running from the leading edge to the trailing edge of the wing. The ribs give the wing its contou
48、r and shape and transmit the load from the skin to the spars. Ribs are also used in ailerons, elevators, fins, and stabilizers. Figure 1-7 shows three general rib constructions: the former, reinforced, and truss ribs. Each type is discussed separately in the following paragraphs. Former ribs, locate
49、d at frequent intervals throughout the wing, are made of formed sheet metal and are very lightweight. The bent-up portion of a former rib is the flange and the vertical portion is the web. The latter is generally made with beads pressed between the lightening holes. These holes lessen the ribs weight without decreasing its strength. Lightening hole area rigidity is ensured by flanging the edges of the holes. The reinforced rib is similar in construction to the spar, consisting of upper and lower capstrips joined by a web plate. Vertical and diagonal angles between the
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