: 43.13-1A Page vil 72 TABLE OF CONTENTS- Continued Section 2. REPAIR OF WOOD AND COMPOSITION PROPELLERS Paragraph Page
567. General 215
668. Repair of Wood Propellers 215
569. Repair of Composition Blade 220
570. Refinishing 222
571. Propeller Balancing 222
572.-582. Reserved 222 Section 3. REPAIR OF METAL PROPELLERS 228 Steel Blades 228
585. Aluminum Propeller Repaire 228 Repair Tolerances 229 Propeller Balance 228
588. Steel Hubs and Hub Parts 280 Propeller Hub and Flange Repair 280
590. Control Systema 280
591. Deicing Systems 280
592.-602. Reserved 280 Section 4. OVERHAUL OF PROPELLERS
608. Hub and Hub Parts 282
604. Plating for Hubs and Parts 282
605. Inspection of Aluminum Propellers and Blades 282
606. Assembly 288
607.-617. Reserved 288 Section 5. ASSEMBLY OF PROPELLER TO ENGINE
618. Fixed-Pitch Propellers 284
619.-629. Reserved 284 Section 6. PRECAUTIONS
680. Blade-Tip Identification 285
631. Ground-Handling Practices 285
682. Composition Propeller Service Limits 285
688.-648. Reserved 285 Section 7. MAINTENANCE OF ROTOR BLADES
644. General 286
645.-655. Reserved 241 Chapter 13. WEIGHT AND BALANCE
656. General 248
657. Terminology 248
658. Weighing Procedure 250
659. Weight and Balance Computations 258
660. Weight and Balance Extreme Conditions 258
661. Loading Conditions and/or Placards 257
662. Equipment List 257
668. Sample Weight and Balance Report 257
664. Installation of Ballast 258
665. Loading Schedule 265
666.-676. Reserved 265
Page vill AC 43.13- 19 TABLE OF CONTENTS- Continued Chapter 14. ENGINES AND FUEL SYSTEMS Section 1. ENGINES Paragraph Page
677. General 267
678. inspection 267
679. Powerplant Sudden Stoppage - 267
680. Crankshafts - 269
681. Replacement Parts in Certificated Engines 289
682. Cylinder Holddown Nuts and Capscrews 270
688. Reuse of Safetying Devices 270
684. Self-Locking Nuts for Aircraft Engines and Accessories 270
685. Welding of Highly Stressed Engine Parts 271
686. Welding of Minor Engine Parte 271
687. Metallizing 271
688. Plating 271
689. Engine Accessories 272
690. Corrosion 272
691. Engine Run-In 272
692. Compression Testing of Aircraft Engine Cylinders 212
698. Spark Plugs 274
694. Ignition Harnesses 278
695. Magneto Inspection 278
696. Magneto-to-Engine Timing 280 697-707. Reserved 280 Section 2. FUEL SYSTEMS
708. General 281
709. Fuel Lines and Fittings 281
710. Fuel Tanks and Cella 282
711. Fuel Tank Caps, Vents, and Overflow Lines 282
712. Fuel Crossfeed, Firewall Shutoff, and Tank Selector Valves 288
718. Fuel Pumps 288
714. Fuel Filters, Strainers, and Drains 288
716. Indicator Systems 288
716. Turbine Fuel Systems 288
717.-727. Reserved 284 Section 3. EXHAUST SYSTEMS
728. General
729. Muffer/Heat Exchanger Failures
780. Manifold/Stack Failures 285
781. Internal Muffler Failures 285 782- Inspection 288
788. Repairs 288
784. Turbosupercharger 290
785. Augmentor Systems 290
786.-746. Reserved 290 Chapter 15. RADIO AND ELECTRONIC SYSTEMS Section 1. MAINTENANCE OF RADIO AND ELECTRONIC SYSTEMS
747. General 291
748. Maintenance of Equipment 291
749. Replacement of Components 291
760. Inspection of Installations 291
AC 43,13-14 Page ix 1972 TABLE OF CONTENTS- Continued Paragraph Page
751. Cleaning 291
752. Contact Cleaners 291
758. Operational Checks 292
754.-765. Reserved 292 Section 2. MAINTENANCE OF WIRING AND CABLES
766. Wiring and Cable Integrity 767- Protection from Fluids
768. Wire and Cable Clamps
769. Conduit
770. Plastic Wire Sleeving
771. Electrical Tape
772.-782. Reserved Section 3. JUNCTION BOXES AND TERMINAL STRIPS
788. Junction Boxes
784. Internal Arrangement
785. Terminal Strips
786. Pluge and Receptacles
787.-797. Reserved Section 4. POWER SOURCES AND DISTRIBUTION SYSTEMS
798. Battery Electrolyte Corrosion 285
799. Generators and Alternators 295
800. Alternator Diodes 295
801. Diode Protection 295
802. Alternator/Battery Connections 295
808. Static Electrical Power Convertera 295
804. Cleaning and Preservation 295
805. Miscellaneous Check Items 295
806. Adjustment and Repair 296
807. Electrical Switch Inspection 296
808. Radio Equipment Operation 296
809.-819. Reserved 296 Section 5. NOISE SUPPRESSION
820. General 297
821. Bonding 297
822. Shielding 297
828. Spark Plugs 297
824. Filters 297
825. Precipitation Static 297
826. Static Dischargers 297
827. Maintenance of Static Dischargers 297
828.-888. Reserved 298 Section 6. ANTENNAS
889. Fixed and Trailing Wire Antennas 299
840. Whip and Blade Antennas 299
841. Flush Mounted Antennas 299
842. Coaxial Cables and Fittings 299
843. Radomes 299
844. Radome Inspection 299
845. Radome Maintenance and Repair 800
846. Loop Antennas 800
847. Loop Quadrantal Error 800
Page x AC 43.13 1A 1972 TABLE OF CONTENTS Continued Paragraph Pane
848. Compensation for Quadrantal Error 800
849. Ground Calibration 801
850. Air Calibration 801
851. Calibration Points 801
852. Calibration Procedure 801
858. Calibration Data 801
854.-868. Reserved 801 Chapter 16. INSTRUMENTS Section 1. MAINTENANCE OF INSTRUMENTS General 808
865. Definition 808
866. Maintenance of Instruments 808
867. Test/Adjustment of Instruments 808
868. Replacement of Components 804
869.-879. Reserved 804 Section 2. INSPECTION AND CHECKS
880. General 805
881. Periodic Inapection 805
882. Additional Inspectiona 805
888.-899. Reserved 805 Section 3. INSTRUMENT POWER SOURCES
894. Electrical Compatibility 806
895. Vacuum Systems 806
896.-906. Reserved 806 Section 4. PITOT-STATIC SYSTEMS
907. System Components 807
908. Pitot-Static Tubes and Lines 807
909. Pressure Porta or Vents 807
910. Cleaning of System 807
911. Heater Elements 807
912. System Leak Testing 807
918. Static System Test 807
914. Pitot System Test 808
915. Precautions in Teating 308
916.-926. Reserved 808 Section 5. MECHANICAL ADJUSTMENT OF MAGNETIC DIRECTION
INDICATORS
927. Correction for Errors 809
928. Ground Swinging 809
929. Remote Gyro Compass Systems 809
980.-940. Reserved 809 Section 6. PRESERVATION AND PACKAGING
941. Preservation 810
942. Storage 810
943. Shipping 810 924-954. Reserved 810 Appendix 1. Cross Reference Table of Paragraph Number Changes 811 Appendix 2. Cross Reference Table of Illustration Number Changes 815
C 43,13-1A Page xi 972
LIST OF ILLUSTRATIONS Pigure Page
1.1 Tapering of Face Plates .. 1
1.2 Selection and Properties of Aircraft Wood
1.8 Consideration of Grain Direction When Making Scarf Joints 6 Method of Splicing Solid or Laminated Rectangular Spars
1.5 Method of Splicing Solid "I" Spars --
1.6 Repaira to Bullt-Up "I' Spar .. 9 1,7 Method of Splicing Box-Spar Flanges (Plate Method) 10
1.8 1.9 Method of Splicing Box-Spar Webs Method of Reinforcing a LongitudInal Crack and/or Local Damage 11 in a Solld or Internally Routed Spar .. 12
1.10 Repair of Wood Ribs 18
1.11 Typical Wing Compression Rib Repairs 14
1.12 Minimum Recommended Bend Radii for Aircraft Plywood 15
1.18 Splayed Patch 16
1.1₫ Surface Patches 18
1.15 Scarf Patches Back of Skin Accessible 19
1.16 Scarf Patches-Back of Skin Not Accessible 20
1.17 Oval Plug Patch Assembly 21
1.18 Round Plug Patch Assembly 22
2.1 Current and Polarity Selection for Inert Gas Welding 29
2.2 Specifications Guide for Welding 81
2.8 Strengths of Welded Joints 82 2,4 Members Dented at a Cluster 88
2.5 Members Dented in a Bay-Repairs by Welded Sleeve 84 2,6 Welded Patch Repair 85
2.7 Splicing by Inner Sleeve Method 86
2.8 Splicing by Outer Sleeve Method-Replacement by Welded Outside Sleeve 87
2.9 Tube Replacement at a Station by Welded Outer Sleeves 88
2.10 Splicing Using Larger Diameter Replacement Tube 89
2.11 Repairs at Built-In Fuselage Fittings 41
2.12 Streamline Tube Splice Using Round Tube (Applicable to Landing Gears) 42
2.18 Streamline Tube Splice Using Split Sleeve (Applicable to Wing and Tail Surface Brace Struts and Other Members) 48
2.14 Streamline Tube Splice Using Split Insert (Applicable to Landing Gears) 44
2.15 Streamline Tube Splice Using Plates (Applicable to Landing Gears) 45
2.16 Representative Types of Repairable and Nonrepairable Axle Assemblies 46
2.17 Recommended Radii for 90° Bends in Aluminum Alloys 50
2.18 Rivet Hole Spacing and Edge Distance for Single-Lap Sheet Splices 52
2.19 Riveting Practice and Rivet Imperfections 58
2.20 Typical Repair Method for Tubular Members of Aluminum Alloy 55
2.21 Typical Repair for Buckled or Cracked Formed Metal Wing Rib Capstripa 56 Typical Metal Rib Repaire (Usually Found on Small and Medium-Size Aircraft) 57
2.28 Typical Repairs of Trailing Edges .. 58 2-24 Typical Repairs of Stressed Sheet Metal Covering 59
2.25 Typical Stringer and Flange Splices 61
2.26 Example of Stringer Splice (Material-2017 Alloy) ₴2
Page xil AC 43.13-1 197 LIST OF ILLUSTRATIONS- Continued Figure Page
2.27 Application of Typical Flange Splices and Reinforcement 68
2.28 Number of Rivets Required for Splices (Single-Lap Joint) in Bare 2014-T6, 8024-18, 2024-T86, and 7075-T6 Sheet, Clad 2014-T6, 2024-T8, 2024-T96 and 7075-T6 Sheet, 2024-T4, and 7075-T6 Plate, Bar, Rod, Tube, and Extrusions, 2014-T6 Extrusions 64
2.29 Number of Rivete Required for Splices (Single-Lap Joint) in 2017, 2017 Alclad, 2024-T86 and 2024-T86 Alclad Sheet, Plate, Bar, Rod, Tube, and Extrusions - 65
2.80 Number of Rivets Required for Splices (Single-Lap Joint) in 5052 (All Hardnesses) Sheet 66
2.81 Example of Splice of Intermediate Frame (Material 2017 AL Alloy) 67
2.82 Typical Methods of Repalring Cracked Leading and Trailing Edges and Rib Intersections - 68
2.88 Typical Methods of Replacing Cracked Members at Fittinga 69
2.84 Typical Methods of Repairing Cracked Frame and Stiffener Combinations 70
2.85 Typical Repairs to Rudder and to Fuselage at Tail Post 71
2.86 Typical Methods of Repairing Elongated or Worn Bolt Holes 72
2.87 Typical Laminate (Facing) Repair 74 2,88 Typical Core and Facing Repair - 75
2.89 Typical Stepped Joint Repair 75
2.40 Typical Scarfed Joint Repair 78
2.41 Typical One Side Blind Repair 76
2.42 Typical Metal Facing Patch
2.48 Typical Types of Core Replacement 78
2.44 Typical Undercut Core Material Cavity 78
8.1 Textile Fabric Used in Aircraft Covering 88
3.2 Miscellaneous Textile Materials 84
8.8 Typical Methods of Attaching Fabric 85
3.4 Standard Knot for Rib Lacing and Terminating a Sewed Seam (Modified Seine Knot) 86
8.6 Splice Knot 87
3.6 Starting Stitch for Rib Stitching 88
8.7 Standard Double Loop Lacing 89
8.8 Standard Knot for Double Loop Lacing 90
8.9 Fabric Attachment Spacing 91
3.10 Repair of Tears in Fabric 95
4.1 Cable Cross Section 99
4.2 Strength of Steel Cable 100
4.8 Straight-Shank Terminal Dimensiona 101
4.4 Insertion of Cable into Terminal 101
4.5 Gauging Terminal Shank After Swaging 101
4.6 Typical Cable Splices 102
4.7 Typical Terminal Gauge 102
4.8 Copper Oval Sleeve Data 108
4.9 Typical Thimble-Eye Splice 108
4.10 Copper Stop Sleeve Data 104
4.11 Typical Terminal Gauge 104
4.12 Preparation of a Woven Cable Splice 106
4.18 Preparation of a Wrapped Soldered Terminal 108
4.14 Cable Inspection Technique 107
4.15 Cable Wear Patterns .- 107
4.16 Worn Cable (Replacement Necessary) 108
4.17 Worn Cable (Replacement Recommended) 108
4.18 Internal Cable Wear 108
4.19 Corrosion 109
4.20 Manufacturer's Wire Splice 109
4.21 Pulley Wear Patterns 110
AC 43.13-1A Page xill 1972 LIST OF ILLUSTRATIONS- Continued Figure Page 4,22 Turnbuckle Safetying Guide 112
4.28 Safetying Turnbuckles 118
4.24 Clip Type Locking Device 114
5.1 Bolt Indentification 116
5.2 Recommended Torque Values For Nut-Bolt Combinations-(without lubrication) . 118
5.8 Torque Wrench With Various Adapters 119
7.1 Numerical System for Steel Identification 129
7.2 Basic Temper Designationa and Subdivisions for Aluminum Alloys 180
7.8 Rockwell C Scale Steel Hardneas Numbers Comparison Table 188 7,4 Hardness Values for Aluminum Alloys 182
7.5 Maximum Recommended X-Ray Kilovolts 188
8.1 Typical Bolt Cracks 141
8.2 Typical Cracke Near Boltholes 142
8.8 Typical Bolthole Cracka 142
8.4 Typical Rod-End Cracks 142
8.5 Typical Torque Tube Bolthole Elongation 142 8,6 Aircraft Tire Types and Ratings 146
8.7 Oxygen Cylinder Damage 155
8.8 Cylinder Brackets and Clamps 156
9.1 Stop-Drilling Cracks 160
9.2 Surface Patches 160
9.8 Plug Patch Repair 161
10.1 Tube Data 165
10.2 Hose Assembly Instructions 167
10.8 Aircraft Hose Specificationa 168
10.4 Proper Hose Installations 169
10.5 Minimum Bend Radif 170
10.6 Ball Diameters for Testing Hose Restrictions or Kinking 171
10.7 Suggested Handling of Preformed Hose 171
10.8 Minimum Bend Radil-Teflon Hose 172
11.1 Wire and Circuit Protector Chart 177
11.2 Switch Derating Factors 177
11.8 Examples Determining Voltage Drop from Electric Wire Chart (Fig. 11.7) 179
11.4 Examples Determining Voltage Drop from Electric Wire Chart (Fig. 11.7) 179
11.5 Copper Electric Wire Current Carrying Capacity 180
11.8 Aluminum Electric Wire Current Carrying Capacity 180
11.7 Electric Wire Chart 182
11.78 Wire Used in Aircraft Installations 188
11.8 Staggered Splices in Wire Bundle 186
11.9 Cable Clamp at Bulkhead Hole 187
11.10 Cable Clamp and Grommet at Bulkhead Hole 187
11.11 Allowable Nicked or Broken Strands .. 188
11.12 Stud Bonding or Grounding to Flat Surface 189
11.18 Plate Nut Bonding or Grounding to Flat Surface 190
11.14 Bolt and Nut Bonding or Grounding to Flat Surface 191
11.15 Copper Jumper Connection to Tubular Structure 192
11.16 Bonding Conduit to Structure 192
11.17 Aluminum Jumper Connection to Tubular Structure 192
11.18 Sizes of Identification Sleeving 104
11.19 Identification of Wire Bundles and Harnesses 195
11.20 AN Connectors 107
11.21 Classes of AN Connectors 187
11.22 AN Connector Marking .. 198
11.28 Spare Wires for Potting Connector 199
11.24 Bend Radil for Rigid Conduit 201
Page xiv AC 43.19-1 197 LIST OF ILLUSTRATIONS- Continued Pioure Page
11.25 Minimum Bending Radii for Flexible Aluminum or Brass Conduit 202
11.26 Group and Bundle Ties 208
11.27 Comb for Straightening Wires in Bundles 208
11.28 Slack Between Supports 204
11.29 Drainage Hole in Low Point of Tubing 204
11.80 Separation of Wires from Plumbing Lines 205
11.81 Safe Angle for Cable Clamps .. 206
11.82 Typical Mounting Hardware for MS-21919 Cable Clamps 206
11.88 Installing Cable Clamp to Structure - 207
11.84 Installing Cable Clamps to Tubular Structure 207
11.85 Single Cord Lacing 208
11.86 Double Cord Lacing 209
11.87 Making Ties.. 209
11.88 Lead-Acid Battery Electrolyte Freezing Points 210
11.89 Sulfuric Acid Temperature Correction 211
12.1 Propeller Repair by Addition of Small Inlay 217
12.2 Method of Repairing Surface Cracks, Nicks, etc., on Aluminum Alloy Propellers 224
12.8 Correct and Incorrect Method of Reworking Leading Edge of Aluminum Alloy Propellers 225
12.4 Repair Limits to Blade Section Width and Thickness for Aluminum Alloy Propellers 226
12.5 Method of Repairing Damaged Tip of Aluminum Alloy Propellers 227
12.6 Protractor and Method of Measuring Angle of Bend in Aluminum Alloy Propellers 228
12.7 Repair of Fixed-Pitch Hub and Propeller With Elongated or Damaged Boltholes 281
12.8 Blade Leading Edge and Trim Tab 287
12.9 Blade Bonding and Crack Location 288
12.10 Blade Damage Location 288
12.11 Blade Cross-Section 289
12.12 Blade Retention and Link Attach Points 240
18.1 Typical Datum Locations 244
18.2 Illustration of Arm (or Moment Arm) 245
18.8 Example of Moment Computation . 246
18.4 Empty Weight Center-of-Gravity Formulas 247
18.5 Empty Welght and Empty Weight Center-of-Gravity-Tail-Wheel Type Aircraft - 248 18,6 Empty Weight and Empty Weight Center-of-Gravity--Nose-Wheel Type Aircraft 249
18.7 Operating Center-of-Gravity Range 250
18.8 Weighing Point Centerline 251
18.9 Empty Weight and Empty Weight Center-of-Gravity When Aircraft is Weighed With Oil 252
18.10 Example of Check of Most Forward Weight and Balance Extreme 254
18.11 Example of Check of Most Rearward Weight and Balance Extreme 255
18.12 Loading Conditions: Determination of the Number of Passengers and Baggage Permissible with Full Fuel 256
18.18 Loading Conditions: Determination of the Fuel and Baggage Permissible with Maximum Passengers 258
18.14 Loading Conditions: Determination of the Fuel and the Number and Location of Passengers Permissible with Maximum Baggage 259
18.15 Effects of the Addition of Equipment Items on Balance 260
18.16 Example of Moment and Weight Changes Resulting from Equipment Changes 261
18.17 Sample Welght and Balance Report To Determine Empty Weight Center-of-Gravity 262
C 43.13-14 Page xY 973 LIST OF ILLUSTRATIONS- Continued Pinurs Page
18.18 Sample Weight and Balance Report Including an Equipment Change for Aircraft Fully Loaded 268
13.19 Permanent Ballast Computation Formula 264
14.1 Schematic of Typical Differential Pressure Compression Tester 278
14.2 Spark Plug Heat Ranges 214
14.8 Spark Plug Reach 275
14.4 Method of Checking Spark Plug Gap . 275
14.58 Typical Carbon Fouled Spark Plug . 276
14.5b Typical Lead Fouled Spark Plug 276
14.бе Typical Oil Fouled Spark Plug 276
14.6а Typical Eroded Spark Plug 277
14.6b Typical Spark Plug With Copper Runout 277
14.7 Typical Spark Plug With Bridged Electrodes 277
14.8 Spark Plug Well Flashover 278
14.9 Typical Method of Clamping Leads 278
14.10 Normal Contact Point -- 279
18.11 Point With Minor Irregularities 279
14.12 Point With Well-Defined Mound 279
14.18 Location of Clamps at Tube Bends 281
14.14 Typical Muffler Wall Fatigue Failure at Exhaust Outlet 285
14.15 Typical Muffer Wall Failure .. 286
14.16 Typical Muffler Wall Fatigue Failure 286
14.17 Typical Fatigue Failure of Muffler End Plate at Stack Inlet 287
14.18 Section of Muffler Showing Typical Internal Baffle Fallure 287
14.19 Loose Pieces of Failed Internal Baffle .. 287 14,20 Failed Internal Baffle Partially Obstructing Muffler Outlet 288
14.21 Failed Internal Baffle Completely Obstructing Muffer Outlet 288
14.22a Example of Exhaust Outlet Guard ... 288
14.22b Example of Exhaust Outlet Guard Installed 289
14.28 Effect of Improperly Positioned Exhaust Pipe/Muffler Clamp 289
14.24 Primary Inspection Areas 290
AC 43.13-1A Page 1 1972 Chapter 1. AIRCRAFT WOOD STRUCTURES Section 1. MATERIALS AND PRACTICES
1. MATERIALS. Three forms of wood are commonly used in aircraft: solid wood, plywood, and laminated wood. Although several kinds of modified wood are sometimes used for special purposes, these three forms constitute the bulk of all wood aircraft construction materials.
a. Quality of Wood. All wood and plywood used in the repair of aircraft structures should be of aircraft quality. Figure 1.2 fists the permissible variations in characteristics and properties of aircraft wood.
bracing and checking or splitting of wood members.
A few suggestions for minimizing these shrinkage effects are:
(1) Use bushings that are slightly short so that when the wood member shrinks the bushings do not protrude and the fittings may be tightened firmly against the member.
(2) Gradually drop off plywood face plates either by feathering or by shaping as shown in figure 1.1.
b. Species Substitution. The species used to repair a part should be the same as that of the original whenever possible; however, permissible substitutes are given in figure 1.2.
c. Effects of Shrinkage. When the moisture content of wood is lowered, its dimensions decrease. The dimensional change is greatest in a tangential direction (across the fibers and parallel to the growth rings), somewhat less in a radial direction (across the fibers and perpendicular to the growth rings), and is negligible in a longitudinal direction (parallel to the fibers). These dimensional changes can have several detrimental effects upon a wood structure, such as loosening of fittings and wire
2. REPLACEMENT OF DRAINHOLES AND SKIN STIF- FENERS. Whenever repairs are made that require replacing a portion that includes drainholes, skin stiffeners, or any other items, the repaired portion must be provided with similar drainholes, skin stiffeners, or items of the same dimensions in the same location. Reinforcing, under skin repairs, that interferes with the flow of water from some source, such as inspection holes, is to be provided with drainholes at the lowest points.
3. CONTROL SURFACE FLUTTER PRECAUTIONS.
When repairing control surfaces, especially on high-performance airplanes, care must be exer-
FEATHERED END/ SPADED END- FIGURE 1.1.-Tapering of face plates.
Chap 1 Par 1
Page 2 AC 43.13-1A 1972 FIGURE 1.2.—Selection and properties of aircraft wood.
Maximum utrength permisaible Species of wood properties as compared to ation (alope Frain devi- Remarks spruce of grain) Spruce (Picea) Sitka (P. Bit- 100% 1:15 Excellent for all us. Considered as standchensle) Red (P. Bubra) ard for this table.
White (P. Glauce).
Douglas Fir (Paeudotsuga Taxi- Exceeds spruce 1:16 May be need as substitute for spruce in same folia). sizes or in alightly reduced sizes providing reductions are substantiated. Difficult to work with hand tools. Some tendency to split and splinter during fabrication and considerable more care in manufacture is necessary. Large solid pleces should be avoided due to Inspection difficulties. Gluing satisfactory.
Noble Fir (Ables Noblies) - Slightly exceede spruce 1:15 Satlafactory characteristics with respect to except 8 percent workability, warping, and splitting. May be deficient in shear. used as direct substitute for spruce In same sizes providing shear does not become critical.
Hardness somewbat less then spruce. Gluing satisfactory.
Western Hemlock (Truga Het- Slightly exceeds spruce 1:15 Less uniform in texture than spruce. Afay be eropbylia). used as direct substitute for spruce. Upland growth superior to lowland growth. Gluing satisfactory.
Pine, Northern White (Pinus Properties hetween 85 1:15 Excellent working qualities and uniform in Strobus). percent and 96 per- propertles but somewhat low in hardness and cent those of spruce. abock-resisting capacity. Cannot be used as substitute for spruce without increase in sizes to compensate for lesser strength. Gluing satisfactory.
White Cedar, Port Oxford Exceeds spruce - (Charaecyparla Lawsoniana).
1:15 Nay be used as substitute for spruce In same sizes or in slightly reduced sizes proriding reductione are substantiated. Easy to work with band toola. Gluing difficult but satistactory joints can be obtained if suitable precau tlone are taken.
Poplar, Yellow (Lirlodendron Slightly leas than 1:15 Excellent working qualities. Should not be Tulipifera). spruce except in used as a direct aubstitute for spruce without compression (crush- carefully accounting for slightly reduced ing) and shear. strength properties. Somewhat low in shockresisting capacity. Gluing satisfactory.
(Bee notes follosoing table.)
Notes for Agure 1.2.
1. Defeots Permitted.
a. Oross grain. Spiral grain, diagonal grain, or a combination of the two is acceptable providing the grain does Par 3
AC 43.13-1A Page 3 1972 not diverge from the longitudinal axis of the material more than specifed in column 8. A check of all four faces of the board is necessary to determine the amount of divergence. The direction of free-flowing ink will frequently assist in determining grain direction.
b. Wacy, ourly, and interlocked grain. Acceptable, if local irregularities do not exceed limitations specifed for spiral and diagonal grain.
c. Eard knots. Sound bard knots up to ¼-inch In maximum diameter are acceptable prorlding: (1) they are not in projecting portions of I-beams, niong the edges of rectangular or beveled unrouted beams, or along the edges of manges of box beams (except in lowly stressed portions); (2) they do not cause grain divergence at the edges of the board or in the fanges of a beam more than specifed in column 8; and (B) they are in the center third of the beam and are not closer than 20 inches to another knot or other defect (pertains to %-inch knots-smaller knots may be proportionately closer). Knote greater than ¾-inch must be used with caution.
d. Pin knot olusters. Small clusters are acceptable providing they produce only a small effect on grain direction.
e. Pitoh pookots. Acceptable, in center portion of a beam providing they are at least 14 inches apart when they lie in the same growth ring and do not exceed 1½ inch length by %-inch width by ⅛-inch depth and providing they are not along the projecting portions of I-beams, along the edges of rectangular or beveled unronted beams, or along the edges of the flanges of box beams.
f. Afineral streaks. Acceptable, providing careful inspection falls to reveal any decay.
2. Defects Not Permitted.
a. Cross grain. Not acceptable, unless within limitations noted in 1a.
D. Wavy, curly, and interlocked grain. Not acceptable, unless within limitatlons noted in 1b.
c. Hard knots. Not acceptable, unless within limitations noted in 1c.
d. Pin knot oluaters. Not acceptable, If they produce large effect on grain direction.
e. Spike knots. These are knots running completely through the depth of a beam perpendicular to the annual ringe and appear most frequently in quartersawed lumber. Reject wood containing this defect.
1. Pitch pockets. Not acceptable, unless within limitations noted in le.
g. fineral streaks. Not acceptable. If accompanied by decay (see 1f).
b. Checks, shakes, and aplits. Checks are longitudinal cracks extending, in general, across the annunl rings.
Shakes are longitudinal cracks usually between two annual rings. Splits are longitudinal cracks induced by artificially induced stress. Reject wood containing these defects.
1. Compression cood. This defect is very detrimental to strength and is difficult to recognize readily. It la characterized by high specific gravits; has the appenrance of an excessive growth of summer wood; and in inost species shows but little contrast in color between epring wood and summer wood. In doubtful cases reject the material, or subject samples to a tonghness machine test to establish the quality of the wood. Reject all materlal containing compression mood.
j. Compressio» failures. This defect ia caused from the wood belng overstressed in compresslon due to natural forces during the growth of the tree, felling trees on rough or irregular ground, or rough handling of logs or lnmber.
Compression failures are choracterized by a buckling of the fbers that appear as streaks on the surface of the piece substantially at right angles to the grain, and rary from pronounced fallures to very fine hairlines that require close inspection to detect. Reject wood containing obvious failures. In doubtful cases reject the wood, or make a further inspection in the form of microscopic examination or toughness test, the latter means being the more rellable.
k. Decay. Examine all stains and discolorations carefully to determine whether or not ther are harmless, or in a stage of preliminary or advanced decay. All pleces must he free from rot, dote, red heart, purple heart, and all other cised that the repairs do not involve the addition of weight aft of the hinge line. Such a procedure may adversely disturb the dynamic and static balance of the surface to a degree which would induce flutter. As a general rule, it will be necessary to repair control surfaces in such a manner that the structure is identical to the original so that the weight distribution and resulting mass balance are not affected in any way.
4. GLUING PRECAUTIONS. Satisfactory glue Chap 1 joints in aircraft will develop the full strength of wood under all conditions of stress. To produce this result, the gluing operation must be carefully controlled so as to obtain a continuous, thin, uniform film of solid glue in the joint with adequate adhesion to both surfaces of the wood. Some of the more important conditions involve:
o. Properly prepared wood surfaces.
b. Glue of good quality, properly prepared.
c. Good gluing technique.
Par 3