AC 43.13-1B

ADVISORY

CIRCULAR

AC 43.13-1B

ACCEPTABLE METHODS,

TECHNIQUES, AND PRACTICES  AIRCRAFT

INSPECTION AND REPAIR

September 8, 1998

DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION Flight Standard Service Regulatory Support Division

For sale by the Superintendent of Documents; U.S. Government Printing Office; Washington, DC 20402

Advisory Circular

TITLE 14 OF THE CODE OF FEDERAL REGULATIONS (14 CFR) GUIDANCE MATERIAL

Contents Paragraph Page

Page 3 Subject: ACCEPTABLE METHODS, TECHNIQUES, AND PRACTICESAIRCRAFT

INSPECTION AND REPAIR Date: 9/8/98 Initiated by: AFS-610 AC No: 43.13-1B Change:

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 also 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:

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.

2. 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

Contents Paragraph Page

Page 4 CHAPTER 1. WOOD STRUCTURE SECTION 1. MATERIALS AND PRACTICES

1-1.......................................................................................................................... GENERAL 1- 1

1-2................................................................................................................................ ......... 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- 2 FIGURE 1-2. .................................................TAPERING OF FACEPLATE 1- 3

1-3........................................................................................MODIFIED WOOD PRODUCTS 1- 3

1-4.......................................................................................................................ADHESIVES 1- 3

1-5............................................................................................... BONDING PRECAUTIONS 1- 5

1-6............................................... PREPARATION OF WOOD SURFACES FOR BONDING 1- 5

1-7..............................................................................................APPLYING THE ADHESIVE 1- 6

1-8........................................................................................ASSEMBLY TIME IN BONDING 1- 6

1-9.............................................................................................. BONDING TEMPERATURE 1- 6

1-10..................................................................................................CLAMPING PRESSURE 1- 7

1-11............................................................................METHOD OF APPLYING PRESSURE 1- 7

1-12.1-17. [RESERVED.]1-8

SECTION 2. HEALTH AND SAFETY

1-18........................................................................................................................GENERAL 1- 9

1-19........................... SANDING IN AREAS OF EXISTING BOND JOINTS AND FINISHES 1- 9

1-20.................................................................HANDLING OF ADHESIVES AND FINISHES 1- 9

1-21.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

SECTION 4. REPAIRS

1-36........................................................................................................................GENERAL 1- 15

1-37.....................................REPLACEMENT OF DRAIN HOLES AND SKIN STIFFENERS 1- 15

Contents Paragraph Page

1-38.........................................................CONTROL SURFACE FLUTTER PRECAUTIONS 1- 15

1-39...............................................................................................................SCARF JOINTS 1- 15 FIGURE 1-4.CONSIDERATION OF GR AIN DIRECTION WHEN MAKING SCARF JOINTS 1-15

1-40..................................................................................................... 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

1-41................................................................................................... SPAR REPLACEMENT 1- 16

1-42................................................................................... SPLICING OF BOX SPAR WEBS 1- 16 FIGURE 1-9. .........................METHOD OF SPLICING BOX SPAR WEBS 1- 21

1-43.........................REPLACING SOLID-TYPE SPARS WITH LAMINATED-TYPE SPARS 1- 16

Contents Paragraph Page

Page vi

1-44..............................................SPAR LONGITUDINAL CRACKS AND LOCAL DAMAGE

.1-16

FIGURE 1-10..METHOD OF REIN FORCING A LONGITUDINAL CRACK

AND/OR LOCAL DAMAGE IN A SOLID SPAR1-22

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.................T YPICAL WING COMPRESSION RIB REPAIRS 1-24

1-47............................................................................................... PLYWOOD SKIN REPAIR

.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 RECOMME NDED 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 PATCH ES (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

SECTION 5. FINISHING WOOD STRUCTURES

1-64GENERAL

.1-35

1-65................................................................................................ ACCEPTABLE FINISHES

.1-35

1-66PRECAUTIONS

.1-35

1-67..........................................................................FINISHING OF INTERIOR SURFACES

.1-36

1-68.........................................................................FINISHING OF EXTERIOR SURFACES

.1-36

1-69.......................................................................FINISHING OF END GRAIN SURFACES

.1-36

Contents Paragraph Page

Page vii

1-70..............................................................................FINISHING WITH FABRIC OR TAPE

.1-37

1-71............................................................................................ SEALING OF BOLT HOLES

.1-37

1-72.1-79. [RESERVED.]1-37

CHAPTER 2. FABRIC COVERING SECTION 1. PRACTICES AND PRECAUTIONS

2-1GENERAL

.2-1

2-2.............................................................................................................PROBLEM AREAS

.2-1

2-3..................................................................................... AIRCRAFT FABRIC-SYNTHETIC

.2-1

2-4......................................................................................... AIRCRAFT FABRIC-NATURAL

.2-2

TABLE 2-1. ................................................ COTTON AND LINEN FABRICS 2-3

2-5................................................................................................ RECOVERING AIRCRAFT

.2-2

TABLE 2-2. ........................ CO TTON AND LINEN, TAPES AND THREADS 2-4

2-6...............................................PREPARATION OF THE STRUCTURE FOR COVERING

.2-2

2-7.................................................................................................................FABRIC SEAMS

.2-5

FIGURE 2-1. ........................................................................FABRIC SEAMS 2-7 FIGURE 2-2....................... T YPICAL METHODS OF ATTACHING FABRIC 2-8

2-8..................................................................................................... COVERING METHODS

.2-9

Contents (continued) Paragraph Page

Page viii

2-9........................................................................................................REINFORCING TAPE

.2-10

FIGURE 2- 3............................................ EXPLODED SIDE VIEW OF RIB 2-10

2-10............................................................................................................................L A C I N G

.2-11

FIGURE 2-4.STANDARD EXTERNAL MO DIFIED SEINE KNOT USED FOR

SINGLE AND DOUBLE RIB LACING2-11

FIGURE 2- 5.................................. STARTING STITCH FOR RIB LACING 2-12 FIGURE 2-6. ....................................STANDARD SINGLE-LOOP LACING 2-13 FIGURE 2-7............... ST ANDARD KNOT FOR DOUBLE-LOOP LACING 2-14 FIGURE 2-8............. ST ANDARD DOUBLE-LOOP LACING (OPTIONAL) 2-15 FIGURE 2-9A.ALTERNATE SEQUENCE TO TIE A MODIFIED SEINE KNOT

FOR RIB LACING2-16

FIGURE 2-9B.ALTERNATE SEQUENCE TO TIE A MODIFIED SEINE KNOT

FOR RIB LACING2-17

FIGURE 2-9C.ALTERNATE SEQUENCE TO TIE A MODIFIED SEINE KNOT

FOR RIB LACING2-18

FIGURE 2-10. ......................................................................SPLICE KNOT 2-19 FIGURE 2-11.BLINDSTITCH LACING - SQUARE KNOT SECURED WITH HALF HITCHES 2-20

2-11........................................................................................................... STITCH SPACING

.2-19

FIGURE 2-12. ..................................... FABRIC ATTACHMENT SPACING 2-21

2-12FASTENERS

.2-21

2-13.............................................................................................................FINISHING TAPE

.2-22

2-14............................................................INSPECTION RINGS AND DRAIN GROMMETS

.2-22

2-15.2-19. [RESERVED.]2-23

SECTION 2. APPLICATION OF DOPE

2-20GENERAL

.2-25

TABLE 2-3............................................SAFET Y TIPS FOR DOPE/PAINT 2-26 TABLE 2-4................................................................... TIPS FOR DOPING 2-26

2-21......................................... DOPE APPLICATION PROCEDURE (NATURAL FABRICS)

.2-26

2-22........................................................................................COVERING OVER PLYWOOD

.2-28

2-23..............................................................................COATING APPLICATION DEFECTS

.2-29

2-24.2-29. [RESERVED.]2-31

SECTION 3. INSPECTION AND TESTING

Contents (continued) Paragraph Page

Page ix

2-30GENERAL

.2-33

2-31...............................................................................................FABRIC IDENTIFICATION

.2-34

2-32...........................................................................................COATING IDENTIFICATION

.2-34

2-33..........................................................STRENGTH CRITERIA FOR AIRCRAFT FABRIC

.2-35

2-34............................................................................................................FABRIC TESTING

.2-35

2-35................................................................................... REJUVENATION OF DOPE FILM

.2-36

2-36.2-41. [RESERVED.]2-36

SECTION 4. REPAIRS TO FABRIC COVERING

2-42GENERAL

.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

Contents (continued) Paragraph Page

Page x Chapter 3. Fiberglass And Plastics SECTION 1. REPAIR OF LIGHT LOAD LAMINATE STRUCTURES

3-1GENERAL

.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 COMPONENT3-4

FIGURE 3-6.BALANCED LAYUP SAME AS ORIGINAL NUMBER OF PLIES,

PLUS ONE EXTRA PLY3-4

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 BA GGING 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.....................T YPICAL TYPES OF CORE REPLACEMENT 3-10 FIGURE 3-11............. T YPICAL 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 HON EYCOMB CORE FROM A TAPERED

CONTROL SURFACE3-11

FIGURE 3-15. .........................REMOVAL OF CORE WITH CORE KNIFE 3-11 FIGURE 3-16. ...............................................DETAILS OF CORE REPAIR 3-12

3-11FINISHING

.3-12

3-12.3-17. [RESERVED.]3-13

SECTION 3. TRANSPARENT PLASTICS

Contents (continued) Paragraph Page

Page xi

3-18GENERAL

.3-15

3-19............................................................................................STORAGE AND HANDLING

.3-15

3-20............................................................ FORMING PROCEDURES AND TECHNIQUES

.3-15

3-21.........................................................................................................................HEATING.

.3-16

FIGURE 3-17. ...................................... HANGING OF ACRYLIC SHEETS 3-16

3-22FORMS

.3-16

3-23..................................................................................................... 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 FO R DRILLING ACRYLIC PLASTICS 3-18 FIGURE 3-20.............. APPLYING PR ESSURE TO ACRYLIC PLASTICS 3-19

Contents (continued) Paragraph Page

Page xii

3-24....................................................................................................REPAIR OF PLASTICS

.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

3-25..............................................CLEANING AND POLISHING TRANSPARENT PLASTIC

.3-21

3-26............................................................................................... REPLACEMENT PANELS

.3-21

3-27..................................................................................... INSTALLATION PROCEDURES

.3-22

3-28.3-39. [RESERVED.]3-22

SECTION 4. WINDSHIELDS, ENCLOSURES, AND WINDOWS

3-40GENERAL

.3-23

FIGURE 3-24.TEMPORARY REPAIRS TO CRACKED WINDSHIELDS OR WINDOWS 3-24

3-41PROTECTION

.3-24

3-42........................................................................................WINDSHIELD INSTALLATION

.3-24

3-43.3-47. [RESERVED.]3-25

Chapter 4. Metal Structure, Welding, And Brazing SECTION 1. IDENTIFICATION OF METALS

4-1GENERAL

.4-1

TABLE 4-1.................................. FE RROUS (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 STAINL ESS AND HEAT-RESISTANT STEELS

NOMINAL COMPOSITION (PERCENT)4-2

4-3...................................................................INTERCHANGEABILITY OF STEEL TUBING

.4-2

4-4.................................................................................... IDENTIFICATION OF ALUMINUM

.4-2

TABLE 4-4.BASIC TEMPER DESIGNAT IONS AND SUBDIVISIONS FROM

ALUMINUM ALLOYS4-3

4-5.4-15. [RESERVED.]4-3

SECTION 2. TESTING OF METALS

4-16.....................................................................................................HARDNESS TESTING

.4-5

4-17......................................................................................ROCKWELL HARDNESS TEST

.4-5

4-18........................................................................................... BRINELL HARDNESS TEST

.4-5