Aircraft Inspection, Repair, and Alterations (2023)

(FAA) Federal Aviation Administration, U.S. Department Of Transportation

Description

Aviation Supplies & Academics, Inc. has been the industry’s trusted source for official FAA publications for over 80 years. Look for the ASA wings to ensure you’re purchasing the latest authentic FAA release.

AC 43.13-1B and AC 43.13-2B are current in 2023.

This handbook for Aviation Maintenance Technicians (AMTs), repair stations, aircraft owners and homebuilders details the standards for acceptable methods, techniques, and practices for the inspection, repair, and alteration of aircraft. It is a combination of the two most important Advisory Circulars (ACs) written by the Federal Aviation Administration (FAA) on this topic?—namely, “Acceptable Methods, Techniques, and Practices: Aircraft Inspection and Repair” (AC 43.13-1B) and “Acceptable Methods, Techniques and Practices: Aircraft Alterations” (AC 43.13-2B)—printed and bound into one volume.

AC 43.13-1B provides details on the materials and practices, health and safety, inspection, repair, and finishes for wood structures, fabric covering, fiberglass and plastics, and metal structures, welding and brazing. It includes chapters dedicated to nondestructive inspection (NDI), corrosion, inspection and protection, aircraft hardware, control cables and turnbuckles, engines, fuel, exhaust, propellers, aircraft systems and components, weight and balance, electrical systems, avionics, and human factors.

AC 43.13-2B is a manual filled with details and instructions for the installation of aircraft components and systems, such as communications, navigation, and emergency systems, anticollision and supplementary lights, skis, oxygen systems in nonpressurized aircraft, rotorcraft external-load devices, cargo slings and external racks, glider and banner tow-hitches, aircraft batteries and more, including guidance on adding or relocating instruments.

These combined manuals provide this pertinent information where no manufacturer repair or maintenance instructions exist. The details and standards for methods and practices covered are applicable to non-pressurized civil aircraft with a gross weight of 12,500 pounds or less. Illustrated throughout; includes a glossary, and a list of useful acronyms and abbreviations.

Sujets

• Sciences et techniques

Informations

• Publié par: Aviation Supplies & Academics, Inc.
• Date de parution: 03 avril 2013
• Nombre de lectures: 0
• EAN13: 9781619540361
• Langue: English
• Poids de l'ouvrage: 20 Mo

Extrait

AIRCRAFT AIRCRAFT INSPECTION, REPAIR & ALTERATIONS Acceptable Methods, Techniques & Practices INSPECTION, REPAIR & ALTERATIONS

B2B

U.S. Department of Transportation FEDERAL AVIATION ADMINISTRATION

Includes: AC 43.13-1B September 1998 (Change 1, Sept. 27, 2001) AC 43.13-2B March 2008

Aircraft Inspection, Repair & Alterations AC 43.13-1B, 1998 AC 43.13-2B, 2008

Aviation Supplies & Academics, Inc. 7005 132nd Place SE Newcastle, Washington 98059-3153

© 2013 Aviation Supplies & Academics, Inc. This electronic publication is comprised of the same content as the Federal Aviation Administration’s ofIcial release of this same title. ASA does not claim copyright on any material published herein that was taken from United States government sources. Hyperlinks and index tags have been incorporated throughout to facilitate ease of use for this electronic version. All rights reserved. No part of this electronic Ile may be reproduced, transmitted, shared, distributed or resold without written permission from the publisher.

AC43.13-1B2B-PD 978-1-56027-903-7

Advisory Circular

 TITLE 14 OF THE CODE OF FEDERAL REGULATIONS (14 CFR) GUIDANCE MATERIAL Subject:ACCEPTABLE METHODS,Date:9/8/98AC No:43.131B TECHNIQUES, AND PRACTICES

AIRCRAFT Initiated by:AFS640 Change: 1 INSPECTION AND REPAIR

1.PURPOSE. This advisory circular (AC) contains methods, techniques, and practices acceptable to the Administrator for the inspection and repair of nonpressurized areas of civil aircraft, only when there are no manufacturer repair or maintenance instructions. This data generally pertains to minor repairs. The repairs identified in this AC may only be used as a basis for FAA approval for major repairs. The repair data may also be used as approved data, and the AC chapter, page, and paragraph listed in block 8 of FAA form 337 when:

2.

a.the user has determined that it is appropriate to the product being repaired;

b.it is directly applicable to the repair being made; and

c.it is not contrary to manufacturer’s data.

CANCELLATION. The AC 43.131A dated 1988 is canceled.

3. REFERENCE: Title 14 of the Code of Federal Regulations part 43, section 43.13(a) states that each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance shall use the methods, techniques, and practices prescribed in the current manufacturer’s maintenance manual or Instructions for Continued Airworthiness prepared by its manufacturer, or other methods, techniques, or practices acceptable to the Administrator, except as noted in section 43.16. FAA inspectors are prepared to answer questions that may arise in this regard. Persons engaged in the inspection and repair of civil aircraft should be familiar with 14 CFR part 43, Maintenance, Preventive Maintenance, Rebuilding, and Alteration, and part 65, Subparts A, D, and E of Certification: Airmen Other Than Flight Crewmembers, and the applicable airworthiness requirements under which the aircraft was type certificated.

4. ACKNOWLEDGMENTS. The FAA would like to thank the following persons and organization for their assistance in producing AC 43.131B: Richard Finch, Richard Fischer, Michael Grimes, Ray Stits, William A. Watkins, and the SAE, Aerospace Electronics and Electrical Systems Division. Acknowledgment is also extended to all in the aviation community who commented on the document.

5. COMMENTS INVITED. Comments regarding this AC should be directed to DOT/FAA; ATTN: Airworthiness Programs Branch, AFS610; PO Box 25082; Oklahoma City, OK 73125

Acting Deputy Director, Flight Standards Service

9/8/98

Paragraph

11. 12.

13. 14. 15. 16. 17. 18. 19. 110. 111. 112.

118. 119. 120. 121.

CONTENTS

CHAPTER 1. WOOD STRUCTURE

AC 43.131B

Page

SECTION 1. MATERIALS AND PRACTICES General..........................................................................................................................................................11 Woods...........................................................................................................................................................11 Figure 11. Relative Shrinkage of Wood Member Due to Drying...........................................................11 Table 11. Selection and Properties of Aircraft Wood............................................................................13 Figure 12. Tapering of Faceplate ............................................................................................................13 ModifiedWoodProducts.............................................................................................................................13 Adhesives......................................................................................................................................................13 Bonding Precautions.....................................................................................................................................15 Preparation of Wood Surfaces for Bonding.................................................................................................15 Applying the Adhesive .................................................................................................................................16 Assembly Time in Bonding..........................................................................................................................16 Bonding Temperature...................................................................................................................................16 Clamping Pressure........................................................................................................................................17 Method of Applying Pressure.......................................................................................................................17 117. [RESERVED.] .............................................................................................................................. 18

SECTION 2. HEALTH AND SAFETY

General..........................................................................................................................................................19 Sanding in Areas of Existing Bond Joints and Finishes...............................................................................19 Handling of Adhesives and Finishes ............................................................................................................19 126. [RESERVED.] .............................................................................................................................. 19

SECTION 3. INSPECTION

127. General........................................................................................................................................................111 128. Types of Deterioration and Damage ..........................................................................................................111 129. Inspection Methods ....................................................................................................................................111 Figure 13. Likely Areas to Incur Structural Damage ............................................................................113 130.
135. [RESERVED.] ............................................................................................................................ 114

136. 137. 138. 139.

140.

141. 142.

143.

SECTION 4. REPAIRS

General........................................................................................................................................................115 Replacement of Drain Holes and Skin Stiffeners.......................................................................................115 Control Surface Flutter Precautions ...........................................................................................................115 Scarf Joints..................................................................................................................................................115 Figure 14. Consideration of Grain Direction When Making Scarf Joints ............................................115 Splicing of Spars.........................................................................................................................................115 Figure 15. Method of Splicing Solid or Laminated Rectangular Spars ................................................117 Figure 16. Method of Splicing Solid “I” Spars .....................................................................................118 Figure 17. Repairs to BuiltUp “I” Spar................................................................................................119 Figure 18. Method of Splicing Box Spar Flanges (Plate Method) .......................................................120 SparReplacement.......................................................................................................................................116 Splicing of Box Spar Webs ........................................................................................................................116 Figure 19. Method of Splicing Box Spar Webs ....................................................................................121 Replacing SolidType Spars With LaminatedType Spars ........................................................................116

Page iii

AC 43.131B

Paragraph

CONTENTS (CONTINUED)

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Page

144. Spar Longitudinal Cracks and Local Damage............................................................................................116 Figure 110. Method of Reinforcing a Longitudinal Crack and/or Local Damage in a Solid Spar.........122 145. Elongated Holes in Spars ...........................................................................................................................118 146. Rib Repairs .................................................................................................................................................118 Figure 111. Repair of Wood Ribs ...........................................................................................................123 Figure 112. Typical Wing Compression Rib Repairs .............................................................................124 147.PlywoodSkinRepair..................................................................................................................................120 148. Determination of Single or Double Curvature ...........................................................................................120 149. Repairs to Single Curvature Plywood Skin................................................................................................120 Table 12. Minimum Recommended Bend Radii for Aircraft Plywood...............................................125 150. Repairs to Double Curvature Plywood Skin ..............................................................................................122 151. Types of Patches.........................................................................................................................................125 Figure 113. Splayed Patch.......................................................................................................................127 Figure 114. Surface Patches ....................................................................................................................128 Figure 115. Scarf Patches (Back of Skin Accessible).............................................................................129 Figure 116. Scarf Patches (Back of Skin Not Accessible)......................................................................130 Figure 117. Oval Plug Patch Assembly...................................................................................................132 Figure 118. Round Plug Patch Assembly................................................................................................133 152. Fabric Patch ................................................................................................................................................131 153.
163. [RESERVED.]............................................................................................................................ 133

164. 165. 166. 167. 168. 169. 170. 171. 172.

21. 22. 23. 24.

25.

26. 27.

28.

Page iv

SECTION 5. FINISHING WOOD STRUCTURES

General........................................................................................................................................................135 Acceptable Finishes....................................................................................................................................135 Precautions..................................................................................................................................................135 Finishing of Interior Surfaces .....................................................................................................................136 Finishing of Exterior Surfaces....................................................................................................................136 Finishing of End Grain Surfaces ................................................................................................................136 Finishing with Fabric or Tape ....................................................................................................................137 Sealing of Bolt Holes..................................................................................................................................137 179. [RESERVED.]............................................................................................................................ 137

CHAPTER 2. FABRIC COVERING

SECTION 1. PRACTICES AND PRECAUTIONS

General..........................................................................................................................................................21 Problem Areas ..............................................................................................................................................21 AircraftFabricSynthetic..............................................................................................................................21 AircraftFabricNatural.................................................................................................................................22 Table 21. Cotton and Linen Fabrics...........................................................................................................23 Recovering Aircraft ......................................................................................................................................22 Table 22. Cotton and Linen, Tapes and Threads.......................................................................................24 Preparation of the Structure for Covering ....................................................................................................22 Fabric Seams.................................................................................................................................................25 Figure 21. Fabric Seams..............................................................................................................................27 Figure 22. Typical Methods of Attaching Fabric........................................................................................28 Covering Methods ........................................................................................................................................29

9/8/98

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29.

210.

211.

212. 213. 214. 215.

220.

221. 222. 223. 224.

230. 231. 232. 233. 234. 235. 236.

CONTENTS (CONTINUED)

AC 43.131B

Page

ReinforcingTape........................................................................................................................................210 Figure 23. Exploded Side View of Rib .................................................................................................210 Lacing .........................................................................................................................................................211 Figure 24. Standard External Modified Seine Knot Used for Single and Double Rib Lacing.............211 Figure 25. Starting Stitch for Rib Lacing ..............................................................................................212 Figure 26. Standard SingleLoop Lacing ..............................................................................................213 Figure 27. Standard Knot for DoubleLoop Lacing..............................................................................214 Figure 28. Standard DoubleLoop Lacing (Optional)...........................................................................215 Figure 29a. Alternate Sequence to Tie a Modified Seine Knot for Rib Lacing .....................................216 Figure 29b. Alternate Sequence to Tie a Modified Seine Knot for Rib Lacing .....................................217 Figure 29c. Alternate Sequence to Tie a Modified Seine Knot for Rib Lacing .....................................218 Figure 210. Splice Knot...........................................................................................................................219 Figure 211. Blindstitch Lacing  Square Knot Secured with Half Hitches .............................................220 StitchSpacing.............................................................................................................................................219 Figure 212. Fabric Attachment Spacing..................................................................................................221 Fasteners .....................................................................................................................................................221 Finishing Tape ............................................................................................................................................222 Inspection Rings and Drain Grommets ......................................................................................................222 219. [RESERVED.] ............................................................................................................................ 223

SECTION 2. APPLICATION OF DOPE

General........................................................................................................................................................225 Table 23. Safety Tips for Dope/Paint...................................................................................................226 Table 24. Tips for Doping....................................................................................................................226 Dope Application Procedure (Natural Fabrics) .........................................................................................226 CoveringOverPlywood.............................................................................................................................228 Coating Application Defects ......................................................................................................................229 229. [RESERVED.] ............................................................................................................................ 231

SECTION 3. INSPECTION AND TESTING

General........................................................................................................................................................233 Fabric Identification ...................................................................................................................................234 CoatingIdentification.................................................................................................................................234 Strength Criteria for Aircraft Fabric...........................................................................................................235 FabricTesting.............................................................................................................................................235 Rejuvenation of Dope Film ........................................................................................................................236 241. [RESERVED.] ............................................................................................................................ 236

SECTION 4. REPAIRS TO FABRIC COVERING

242. General........................................................................................................................................................237 243. Repair of Tears and Access Openings........................................................................................................237 Figure 213 Repair of Tears in Fabric .....................................................................................................238 244. SewnPatch Repair .....................................................................................................................................238 Figure 214 HandStitch Detail................................................................................................................239 245. DopedOn Patch Repair .............................................................................................................................239 246.
251. [RESERVED.] ............................................................................................................................ 240

Page v

AC 43.131B

Paragraph

CONTENTS (CONTINUED)

CHAPTER 3. FIBERGLASS AND PLASTICS

SECTION 1. REPAIR OF LIGHT LOAD LAMINATE STRUCTURES

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Page

31. General..........................................................................................................................................................31 32. Fiberglass Laminate Repairs ........................................................................................................................31 Figure 31. Typical Laminate (Facing) Repair .........................................................................................32 Figure 32. Typical Core and Facing Repair ............................................................................................32 Figure 33. Typical Stepped Joint Repair.................................................................................................33 33. Repairing Holes ............................................................................................................................................33 Figure 34. Preparing the Fiberglass Sandwich........................................................................................33 Figure 35. Scarfed Repair to a Nonstructural Laminated Fiberglass Component ..................................34 Figure 36. Balanced Layup Same as Original Number of Plies, Plus One Extra Ply.............................34 Figure 37. Typical Scarf Joint Repair .....................................................................................................35 Figure 38. Carefully Cut Through Each Layer of Fiberglass Cloth and Remove it From the Damaged Area ......................................................................................35 34. Sample Bagging and Curing Process ...........................................................................................................35 Figure 39. Sample Bagging Layup Cross Section...................................................................................36 35.
39. [RESERVED.].................................................................................................................................. 38

SECTION 2. METALLIC SANDWICH SECONDARY STRUCTURE REPAIRS

310. Repairs to Metallic Sandwich Secondary Structure.....................................................................................39 Figure 310. Typical Types of Core Replacement ...................................................................................310 Figure 311. Typical Undercut Core Material Cavity ..............................................................................310 Figure 312. Cross Section of Bonded and Bolted Overlap Repairs .......................................................311 Figure 313. Honeycomb Core Removal..................................................................................................311 Figure 314. Removing Honeycomb Core from a Tapered Control Surface...........................................311 Figure 315. Removal of Core with Core Knife .......................................................................................311 Figure 316. Details of Core Repair .........................................................................................................312 311.Finishing.....................................................................................................................................................312 312.
317. [RESERVED.]............................................................................................................................ 313

318. 319. 320. 321.

322. 323.

Page vi

SECTION 3. TRANSPARENT PLASTICS

General........................................................................................................................................................315 Storage and Handling .................................................................................................................................315 Forming Procedures and Techniques .........................................................................................................315 Heating........................................................................................................................................................316 Figure 317. Hanging of Acrylic Sheets ...................................................................................................316 Forms ..........................................................................................................................................................316 Forming Methods .......................................................................................................................................317 Table 31. Typical Temperatures for Forming Acrylic Sheets .............................................................317 Figure 318. Drill Having an Included Angle of Approximately 150°, Used to Drill Acrylic Plastics...............................................................................................318 Figure 319. Unibit Drill for Drilling Acrylic Plastics .............................................................................318 Figure 320. Applying Pressure to Acrylic Plastics..................................................................................319

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324.

325. 326. 327. 328.

340.

341. 342. 343.

CONTENTS (CONTINUED)

AC 43.131B

Page

RepairofPlastics........................................................................................................................................319 Figure 321. StopDrilling Cracks ............................................................................................................320 Figure 322. Surface Patches ....................................................................................................................320 Figure 323. Plug Patch Repair.................................................................................................................321 Cleaning and Polishing Transparent Plastic...............................................................................................321 Replacement Panels....................................................................................................................................321 Installation Procedures ...............................................................................................................................322 339. [RESERVED.] ............................................................................................................................ 322

SECTION 4. WINDSHIELDS, ENCLOSURES, AND WINDOWS

General........................................................................................................................................................323 Figure 324. Temporary Repairs to Cracked Windshields or Windows..................................................324 Protection....................................................................................................................................................324 Windshield Installation...............................................................................................................................324 347. [RESERVED.] ............................................................................................................................ 325

CHAPTER 4. METAL STRUCTURE, WELDING, AND BRAZING

SECTION 1. IDENTIFICATION OF METALS 41. General..........................................................................................................................................................41 Table 41. Ferrous (Iron) Alloy Materials...............................................................................................41 42. Identification of Steel Stock .........................................................................................................................41 Table 42. Numerical System for Steel Identification.............................................................................42 Table 43. Examples of Stainless and HeatResistant Steels Nominal Composition (Percent)..............43 43. Interchangeability of Steel Tubing ...............................................................................................................42 44.IdentificationofAluminum..........................................................................................................................42 Table 44. Basic Temper Designations and Subdivisions from Aluminum Alloys................................44 45.
415. [RESERVED.] ................................................................................................................................ 44

SECTION 2. TESTING OF METALS

416. Hardness Testing ..........................................................................................................................................45 417.RockwellHardnessTest...............................................................................................................................45 418. Brinell Hardness Test ...................................................................................................................................45 419. Vickers Hardness Test..................................................................................................................................46 420. Microhardness Testing .................................................................................................................................46 421.Indentions.....................................................................................................................................................47 Figure 41. Comparison of Indentation Made by Knoop and Vickers Indenters in the Same Work Metal and at the Same Loads...................................................................47 422. Magnetic Testing ..........................................................................................................................................48 423. Aluminum Testing ........................................................................................................................................48 Table 45. Hardness Values for Aluminum Alloys. (Reference MILH6088G.).................................48 424.
.............................................................................................................................. 48435. [RESERVED.]

Page vii

AC 43.131B

Paragraph

436. 437. 438. 439.

450. 451. 452. 453. 454. 455.

456.

457.

458.

CONTENTS (CONTINUED)

SECTION 3. PRECAUTIONARY MEASURES

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Page

Flutter and Vibration Precautions.................................................................................................................49 Load Factors for Repairs ............................................................................................................................410 Transfer of Stresses Within a Structure......................................................................................................410 449. [RESERVED.]............................................................................................................................ 410

SECTION 4. METAL REPAIR PROCEDURES

General........................................................................................................................................................411 Riveted (or Bolted) Steel TrussType Structures .......................................................................................411 Aluminum Alloy Structures........................................................................................................................411 Selection of Aluminum for Replacement Parts ..........................................................................................412 Heat Treatment of Aluminum Alloy Parts .................................................................................................412 Bending Metal ............................................................................................................................................413 Table 46. Recommended Radii for 90Degree Bends in Aluminum Alloys .......................................414 Setback........................................................................................................................................................413 Figure 42. Setback for a 90Degree Bend .............................................................................................413 Table 47. KChart for Determining Setback for Bends Other Than 90 Degrees ................................415 Figure 43. Methods of Determining Setbacks for Bends Other Than 90 Degrees ...............................416 Riveting.......................................................................................................................................................414 Figure 44. Rivet Identification and Part Number Breakdown ..............................................................416 Table 48. Aircraft Rivet Identification.................................................................................................417 Figure 45. Rivet Hole Spacing and Edge Distance for SingleLap Sheet Splices................................420 Figure 46. Riveting Practice and Rivet Imperfections ..........................................................................421 Figure 47. Self Plugging FrictionLock Cherry Rivets .........................................................................422 Figure 48. MechanicalLock (Bulbed Cherry) Cherry Rivet ................................................................423 Figure 49. Cherry Max Rivet.................................................................................................................424 Figure 410. OlymicLok Rivet ................................................................................................................425 Figure 411. Huck Rivet ...........................................................................................................................426 Repair Methods and Precautions for Aluminum Structure ........................................................................425 Figure 412. Typical Repair Method for Tubular Members of Aluminum Alloy....................................428 Figure 413. Typical Repair for Buckled or Cracked Metal Wing Rib Capstrips ...................................429 Figure 414. Typical Metal Rib Repairs (Usually Found on Small and MediumSize Aircraft).............430 Figure 415. Typical Repairs of Trailing Edges .......................................................................................431 Figure 416. Typical Repairs of Stressed Sheet Metal Coverings ...........................................................432 Figure 417. Typical Stringer and Flange Splices ....................................................................................433 Figure 418. Example of Stringer Splice (Material2017 Alloy) .............................................................434 Figure 419. Application of Typical Flange Splices and Reinforcement.................................................435 Table 49. Number of Rivets Required for Splices (SingleLap Joint) in Bare 2014T6, 2024T3, 2024T3, and 7075T6 Sheet, Clad 2014T6, 2024T3, 2024T36, and 7075T6 Sheet, 2024T4, and 7075T6 Plate, Bar, Rod, Tube, and Extrusions, 2014T6 Extrusions ........................................................437 Table 410. Number of Rivets Required for Splices (SingleLap Joint) in 2017, 1017 Alclad, 2024T3 Alclad Sheet, Plate, Bar, Rod, Tube, and Extrusions ...........................................................................................................438 Table 411. Number of Rivets Required for Splices (SingleLap Joint) in 5032 (All Hardnesses) Sheet ...........................................................................................439

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459.

460.

461. 462. 463.

474.

475. 476. 477. 478. 479. 480. 481. 482. 483. 484. 485. 486.

487.

488.

489. 490.

491.

492.

CONTENTS (CONTINUED)

AC 43.131BCHG 1

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Repairing Cracked Members......................................................................................................................440 Figure 420. Example of Intermediate Frame Stringer Splice (Material 2017T3 AL Alloy).................441 Figure 421. Typical Methods of Repairing Cracked Leading and Trailing Edges and Rib Intersections ..................................................................................................................................442 Figure 422. Typical Methods of Replacing Cracked Member at Fittings ..............................................443 Figure 423. Typical Methods of Repairing Cracked Frame and Stiffener Combination .......................444 Figure 424. Typical Repairs to Rudder and to Fuselage at Tail Post .....................................................445 Steel and Aluminum Fittings ......................................................................................................................440 Figure 425. Typical Methods of Repairing Elongated or Worn Bolt Holes...........................................446 Castings.......................................................................................................................................................440 Selective Plating in Aircraft Maintenance..................................................................................................440 473. [RESERVED.] ............................................................................................................................ 451

SECTION 5. WELDING AND BRAZING General........................................................................................................................................................453 Table 412. Current and Polarity Selection for Inert Gas Welding ........................................................454 Figure 426. Common Defects to Avoid when Fitting and Welding Aircraft Certification Cluster........455 Table 413. Torch Tip Sizes ....................................................................................................................455 Figure 427 ButtWelding Strength Calculations ....................................................................................456 Equipment Selection...................................................................................................................................453 Accurately Identify the Type of Material to be Repaired ..........................................................................454 PreparationforWelding.............................................................................................................................454 Inspection of a Completed Weld................................................................................................................454 Microfissures ..............................................................................................................................................455 Nondestructive Testing...............................................................................................................................455 Practices to Guard Against .........................................................................................................................455 Torch Size (Oxyacetylene welding) ...........................................................................................................455 Welding Rods and Electrodes ....................................................................................................................456 RosetteWelds.............................................................................................................................................456 HeatTreated Members...............................................................................................................................456 Types of Welding .......................................................................................................................................456 Figure 428. Basic GasWelding Flames: Each has Distinctive Shape, Color and Sound. Neutral Flame is the Most Used...........................................................................................457 Figure 429. Set TIG Welder to DC Current, Straight Polarity for Welding Mild Steel, Stainless Steel and Titanium ................................................................................................458 Figure 430. Set TIG to AC Current for Welding Aluminum and Magnesium .......................................458 ElectricResistance Welding ......................................................................................................................458 Figure 431. In Spot Welding, Heat is Produced by Electrical Resistance Between Copper Electrodes. Pressure is Simultaneously Applied to Electrode Tips to Force Metal Together to Complete Fusing Process. SpotWeldNugget Size is Directly Related to Tip Size .............................................................................................458 Brazing........................................................................................................................................................459 Table 414. Calculated Allowable Strength of Base Metal.....................................................................460 Figure 432. Silver Brazing Joints ............................................................................................................460 Figure 433. Electric Soldering Iron.........................................................................................................461 Aircraft Parts Not to be Welded................................................................................................................462 Welding Rod Selection...............................................................................................................................462 Table 415. Chart Showing Welding Filler Rod Selection .....................................................................463 Repair of Tubular Members .......................................................................................................................462 Figure 434. Finger Patch Repairs for Members Dented at a Cluster ......................................................464 Repair by Welded Sleeve ...........................................................................................................................465 Figure 435. Members Dented in a Bay (Repairs by Welded Sleeve) .....................................................466

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