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Aviation Supplies & Academics, Inc.Newcastle, Washington

Aviation Mechanic

HandbookSixth Editionby Dale Crane

Aviation Mechanic Handbook, Sixth EditionDale Crane

Aviation Supplies & Academics, Inc.7005 132nd Place SENewcastle, Washington 98059-3153Website: www.asa2fly.comEmail: [email protected]

©1992–2011 Aviation Supplies & Academics, Inc.All rights reserved. Sixth Edition 2011.

Acknowledgments: Greg Mellema/Abaris, Section 17; Champion Aviation Products, Appendix 2; Concorde Battery, Appendix 3; Michelin Aircraft Tire, Appendix 4.

Printed in the United States of America

2014 2013 2012 2011 9 8 7 6 5 4 3 2 1

ISBN 1-56027-910-9 978-1-56027-910-5ASA-MHB-MICHELIN

Library of Congress Cataloging-in-Publication Data:Crane, Dale. Aviation mechanic handbook / by Dale Crane p. cm. “ASA-M-HB1”—T.p. verso. 1. Airplanes — Maintenance and repair — Handbooks, manuals, etc. I. Aviation Supplies & Academics, Inc. II. Title. TL671.9.C6648 1992 629.134'6 — dc20 92-34331 CIP

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Introduction

Your time as an aviation mechanic is too valuable to be spent looking through stacks of reference books to find a particular chart, formula or diagram you need on a particular job. The editorial staff at ASA has done this job for you and compiled this Aviation Mechanic Handbook to be a handy toolbox source of useful information.

For your convenience, this handbook is arranged in 17 sections with a table of contents at the beginning of each section, as well as a complete table of contents at the front of the book and index at the back.

This information has been compiled from a large number of industry and government publications, and every effort has been made to ensure its applicability and accuracy.

The ASA Aviation Mechanic Handbook is a companion volume to the ASA Dictionary of Aeronautical Terms. The two books are the core of ASA’s training materials for aircraft mechanics.

ASA is dedicated to providing quality training materials for the aviation industry. Your feedback regarding our books will help us to continue to produce the materials you need. Visit the ASA website often (www.asa2fly.com) to find updates to operations and procedures due to FAA changes that may affect this publication, downloadable from ASA’s Product Update pages.

ASA and the author wish to thank Greg Mellema of Abaris Training for his contribution of the material for Section 17, “Composites” for the Third Edition of the Aviation Mechanic Handbook.

Dale Crane, Editor

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Contents

Introduction ..............................................................................................iii

Section 1: General Information ...........................................................1

1.1 Fraction, Decimal, and Metric Equivalents ......................................... 3

1.2 Conversions ........................................................................................ 4

1.3 Aircraft Nomenclature ....................................................................... 13

Axes of an Airplane ...................................................................... 13

Forces Acting on an Aircraft in Flight............................................ 13

Types of Aircraft Structure ............................................................ 14 Truss ......................................................................................... 14 Monocoque............................................................................... 14 Semimonocoque ...................................................................... 15

1.4 Joint Aircraft System/Component (JASC) Code ............................... 16

1.5 Aircraft Nationality Identification ....................................................... 28

1.6 Title 14 of the Code of Federal Regulations ..................................... 31

1.7 Standard Taxi Signals ....................................................................... 34

Section 2: Physical and Chemical .................................................. 35

Periodic Table of Elements ............................................................... 36

2.1 Temperature Conversion .................................................................. 37 Absolute Temperature .................................................................. 42

2.2 ICAO Standard Atmosphere ............................................................. 43

2.3 Distribution of Electrons in the Chemical Elements .......................... 44

2.4 Density of Various Solids and Liquids .............................................. 47 Density of Various Gases ............................................................. 47

2.5 Hydraulic Relationships .................................................................... 48

2.6 Quantity of Liquid in a Drum ............................................................. 50 Estimating Quantity of Liquid in a Standard 55-Gallon Drum ....... 50

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Section 3: Mathematics ..................................................................... 51

3.1 Measurement Systems ..................................................................... 53 The International System of Units (SI) ......................................... 53 The Metric System ....................................................................... 54 U.S. – Metric Conversion .............................................................. 54 Length ...................................................................................... 54 Weight ...................................................................................... 55 Volume ..................................................................................... 55

3.2 Mathematical Constants ................................................................... 56

3.3 Mathematical Symbols ..................................................................... 57

3.4 Squares, Square Roots, Cubes, Cube Roots of Numbers ............... 58

3.5 Diameter, Circumference and Area of a Circle ................................. 61

3.6 Geometric Formulas ......................................................................... 64 Triangle ......................................................................................... 64 Square .......................................................................................... 64 Rectangle ..................................................................................... 64 Parallelogram ............................................................................... 64 Trapezoid ...................................................................................... 64 Regular Pentagon......................................................................... 65 Regular Hexagon ......................................................................... 65 Regular Octagon .......................................................................... 65 Circle ............................................................................................ 65 Ellipse ........................................................................................... 65 Sphere .......................................................................................... 66 Cube ............................................................................................. 66 Rectangular Solid ......................................................................... 66 Cone ............................................................................................. 66 Cylinder ........................................................................................ 66

3.7 Trigonometric Functions ................................................................... 67

3.8 Powers of Ten ................................................................................... 71

3.9 Number Systems .............................................................................. 74 Binary Equivalent of Decimal ....................................................... 74 Octal Equivalent of Decimal ......................................................... 74 Binary Equivalent of Octal ............................................................ 74 Hexadecimal Number System ...................................................... 74 Binary Coded Decimal Equivalent of Decimal .............................. 75 The Gray Code ............................................................................. 75 American Standard Code for Information Interchange (ASCII) .... 75 Special Control Functions Used in ASCII ..................................... 77

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Section 4: Aircraft Drawings ............................................................ 79

4.1 Types of Aircraft Drawings ................................................................ 81 Sketches ....................................................................................... 81 Detail Drawings ............................................................................ 81 Assembly Drawings ...................................................................... 81 Installation Drawings .................................................................... 81 Sectional Drawings ....................................................................... 81 Cutaway Drawing.......................................................................... 81 Exploded-View Drawing ............................................................... 81 Schematic Diagram ...................................................................... 82 Block Diagram .............................................................................. 82 Repair Drawings ........................................................................... 82 Wiring Diagrams ........................................................................... 82 Pictorial Diagrams ........................................................................ 82 Orthographic Projections .............................................................. 82

4.2 Meaning of Lines .............................................................................. 83

4.3 Material Symbols .............................................................................. 84

4.4 Location Identification ....................................................................... 85 Fuselage Stations ......................................................................... 85 Water Lines .................................................................................. 85 Butt Lines ..................................................................................... 85 Wing and Horizontal Stabilizer Stations ....................................... 85

Section 5: Aircraft Electrical Systems .......................................... 87

5.1 Electrical Symbols ............................................................................ 89

5.2 Alternating Current Terms and Values .............................................. 97

5.3 Ohm’s Law Relationships ................................................................. 98

5.4 Electrical Formulas ......................................................................... 100 Formulas Involving Resistance ................................................... 100 Formulas Involving Capacitance ................................................ 101 Formulas Involving Inductance ................................................... 103 Formulas Involving Both Capacitance and Inductance .............. 106 Resonant Frequency .............................................................. 106 Total Reactance ...................................................................... 106 Impedance.............................................................................. 106

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5.5 Electrical System Installation .......................................................... 107 Selection of Wire Size ................................................................ 107 Notes on Wire Installation........................................................... 112 Switch Derating Factors ............................................................. 114 Wire and Circuit Protectors ........................................................ 115 MS Electrical Connectors ........................................................... 116 Resistor Color Code ................................................................... 120 Aircraft Storage Batteries ........................................................... 122 Lead-Acid Batteries ................................................................ 122 Nickel-Cadmium Batteries ...................................................... 123

Section 6: Aircraft Materials ..........................................................125

6.1 Composition of Wrought Aluminum Alloys...................................... 127

6.2 Four-Digit Designation System for Wrought Aluminum Alloys ........ 128

6.3 Mechanical Properties of Aluminum Alloys .................................... 129

6.4 Temper Designations for Aluminum Alloys ..................................... 130 Heat-Treatable Alloys ................................................................. 130 Non-Heat-Treatable Alloys .......................................................... 130

6.5 Temperatures for Heat Treatment of Aluminum Alloys .................... 131

6.6 Bearing Strength (in pounds) of Aluminum Alloy Sheet ................. 132

6.7 Shear Strength of Aluminum Alloy Rivets ....................................... 133 Single-Shear Strength (in pounds) of Aluminum-Alloy Rivets .... 133 Double-Shear Strength (in pounds) of Aluminum-Alloy Rivets ... 133

6.8 SAE Classification of Steel ............................................................. 134

6.9 Strength of Steel Related to its Hardness ...................................... 135

6.10 Color of Steel for Various Temperatures ......................................... 136

6.11 Color of Oxides on Steel at Various Tempering Temperatures ....... 137

Section 7: Tools for Aircraft Maintenance .................................139

7.1 Measuring and Layout Tools ........................................................... 141 Steel Rule ................................................................................... 141 Hook Rule ................................................................................... 141 Combination Set ......................................................................... 141 Dividers ...................................................................................... 142 Outside Calipers ......................................................................... 142 Inside Calipers ............................................................................ 142 Hermaphrodite Calipers ............................................................. 142 Scriber ........................................................................................ 142 Vernier Calipers .......................................................................... 142

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How to Read the Vernier Scale .................................................. 143 Micrometer Caliper ..................................................................... 144 How to Read the Vernier Micrometer Scale ............................... 145 Dial Indicator .............................................................................. 146 Feeler Gages .............................................................................. 146 Small-Hole Gages ...................................................................... 146 Telescoping Gages ..................................................................... 146

7.2 Holding Tools .................................................................................. 147 Vises ........................................................................................... 147 Bench Vise ............................................................................. 147 Drill Press Vise ....................................................................... 147 Pliers .......................................................................................... 147 Combination/Slip Joint Pliers ................................................. 147 Water Pump Pliers ................................................................. 148 Vise-Grip® Pliers ..................................................................... 148 Needle-Nose Pliers ................................................................ 148

7.3 Safety Wiring Tools ......................................................................... 149 Diagonal Cutting Pliers ............................................................... 149 Duckbill Pliers ............................................................................. 149 Safety Wire Twisting Tool ............................................................ 149

7.4 Bending and Forming Tools ............................................................ 150 Tools for Making Straight Bends and Curves ............................. 150 Cornice Brake......................................................................... 150 Box Brake ............................................................................... 150 Press Brake ............................................................................ 150 Slip Roll Former ...................................................................... 151 Forming Compound Curves in Sheet Metal ............................... 151 English Wheel ........................................................................ 151

7.5 Cutting Tools ................................................................................... 151 Shears ........................................................................................ 151 Throatless Shears .................................................................. 151 Squaring Shears .................................................................... 152 Scroll Shears .......................................................................... 152 Hand Shears .............................................................................. 152 Tin Snips ................................................................................ 152 Compound Shears ................................................................. 153 Saws ........................................................................................... 153 Band Saw ............................................................................... 153 Hacksaw ................................................................................. 154

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7.5 Cutting Tools (continued) Wood Saws ................................................................................ 154 Crosscut Saw ......................................................................... 154 Ripsaw .................................................................................... 154 Compass, or Keyhole Saw ..................................................... 154 Backsaw ................................................................................. 155 Chisels ........................................................................................ 155 Flat Chisel .............................................................................. 155 Cape Chisel ............................................................................ 155 Diamond Point Chisel ............................................................. 155 Round Nose Chisel ................................................................ 155 Files ........................................................................................... 156

7.6 Hole Cutting Tools .......................................................................... 157 Twist Drills .................................................................................. 157 Twist Drill Sizes .......................................................................... 157 Drill Gage ................................................................................... 160 Twist Drill Sharpening ................................................................. 160 Drill Point Gage ...................................................................... 161 Large Hole Cutters ..................................................................... 162 Hole Saws .............................................................................. 162 Fly Cutter ................................................................................ 162 Countersink ................................................................................ 162 Reamers ..................................................................................... 163 Drills for Wood and Composite Materials ................................... 163 Auger Bits ............................................................................... 163 Forstner Bits ........................................................................... 164 Flat Wood-Boring Bits............................................................. 164 Brad-Point Drills ..................................................................... 164 Spade Drill .............................................................................. 164

7.7 Threads and Threading Tools ......................................................... 165 Unified and American Standard Thread Form ............................ 165 Thread-Cutting Tools .................................................................. 165 Taps ........................................................................................... 166 Body and Tap Drill Sizes ............................................................. 166 Screw Pitch Gage ....................................................................... 167

7.8 Torque and Torque Wrenches ......................................................... 168 Click-Type Torque Wrench .......................................................... 168 Deflecting-Beam Torque Wrench ................................................ 168 Torque Conversions .................................................................... 170 Recommended Torque Values .................................................... 170

7.9 Pounding Tools ............................................................................... 172 Carpenter’s Claw Hammer ......................................................... 172 Ball Peen Hammer ..................................................................... 172 Metalworking Hammers .............................................................. 172

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Straight Peen and Cross Peen Hammers............................... 172 Body, or Planishing Hammer .................................................. 172 Mallets and Soft-Face Hammers ............................................ 173 Sledge Hammers.................................................................... 173

7.10 Punches ......................................................................................... 173 Prick Punch ................................................................................ 173 Center Punch ............................................................................. 173 Drift, or Starting Punch ............................................................... 173 Pin Punch ................................................................................... 174 Transfer Punch ........................................................................... 174 Automatic Center Punch ............................................................ 174

7.11 Wrenches ....................................................................................... 175 Open End Wrench ...................................................................... 175 Adjustable Open End Wrench ................................................ 175 Ratcheting Open End Wrench ................................................ 175 Box End Wrench ......................................................................... 176 Ratcheting Box Wrench .......................................................... 176 Combination Wrench .................................................................. 176 Flare Nut Wrench ....................................................................... 176 Socket Wrenches ....................................................................... 177 Socket Wrench Handles ......................................................... 177 Hand Impact Tool.................................................................... 177 Typical Socket Wrenches ....................................................... 178 Extension and Adapters ......................................................... 178 Allen Wrenches .......................................................................... 178

7.12 Screwdrivers ................................................................................... 179 Slot Screwdrivers ....................................................................... 179 Offset Screwdriver ...................................................................... 179 Recessed-Head Screwdrivers .................................................... 179 Screw Heads for Special Structural Screws ............................... 180

Section 8: Aircraft Hardware .........................................................181

8.1 Standards ....................................................................................... 183

8.2 Threaded Fasteners ....................................................................... 183 Bolts ........................................................................................... 183 Hex-Head Bolts ...................................................................... 184 Flush-Head Bolts .................................................................... 185 Drilled-Head Bolts .................................................................. 185 Twelve-Point, Washer-Head Bolts .......................................... 185 Internal Wrenching Bolts ........................................................ 185 Clevis Bolts ............................................................................. 186 Eye Bolts ................................................................................ 186 Bolt Installation ........................................................................... 186

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8.2 Threaded Fasteners (continued) Bolt Fits ...................................................................................... 187 Screws ........................................................................................ 187 Aircraft Screw Heads .............................................................. 188 Set Screws ............................................................................. 189 Self-Tapping Sheet-Metal Screws .......................................... 189 Nuts ........................................................................................... 190 Nonlocking Nuts ..................................................................... 190 Self-Locking Nuts ................................................................... 191 Low-temperature locking nuts ............................................ 191 High-temperature locking nuts ........................................... 192 Wing Nuts ............................................................................... 192 Anchor Nuts............................................................................ 192 Channel Nuts.......................................................................... 193 Pressed-Steel Nuts ................................................................ 193 Instrument Nuts ...................................................................... 194 Rivnuts ................................................................................... 194 Threaded Fastener Safetying ..................................................... 195 Locking Washers .................................................................... 195 Cotter Pins.............................................................................. 195 Safety Wire and Safety Wire Twisting ..................................... 196

8.3 Washers ......................................................................................... 199

8.4 Special Rivets ................................................................................. 201 Blind Rivets ................................................................................ 201 Friction-Lock Rivets ................................................................ 202 Mechanical-Lock Rivets ......................................................... 203 CherryMax Rivets, Olympic-Lok Rivets, Huck Rivets ............. 204 High-Strength Pin Rivets ............................................................ 204 Hi-Shear Rivet ........................................................................ 204 Hi-Lok Fasteners .................................................................... 206 Hi-Tigue Fasteners ................................................................. 207

8.5 Cowling Fasteners .......................................................................... 208

8.6 Thread Repair Hardware ................................................................ 209 Helicoil Insert .............................................................................. 209 Acres Sleeves ............................................................................. 210

Section 9: Metal Aircraft Fabrication ..........................................211

9.1 Sheet Metal Layout and Forming ................................................... 213 Definitions ................................................................................... 213 Layout Procedure ....................................................................... 214 Example ................................................................................. 214 Forming .................................................................................. 216

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9.2 Minimum Bend Radii for 90° Bends in Aluminum Alloys ................ 217

9.3 Setback .......................................................................................... 218 Setback (K) Chart ....................................................................... 218

9.4 Bend Allowance Chart .................................................................... 221

9.5 Rivets and Riveting ......................................................................... 224 Alternatives to Riveting ............................................................... 224 Aircraft Solid Rivets .................................................................... 224 Rivet Head Shapes ................................................................ 224 Rivet Material ......................................................................... 225 Rivet Diameter ........................................................................ 225 Examples of Rivet Selection ................................................... 229 Rivet Length ........................................................................... 229 Riveting Tools ............................................................................ 230 Rivet Sets ............................................................................... 230 Bucking Bars .......................................................................... 230 Installing Flush Rivets ................................................................ 231 Blind Rivet Code ......................................................................... 231 Removal of Damaged Rivets ...................................................... 231 Minimum Rivet Spacing and Edge Distance .............................. 232

Section 10: Aircraft Fabric Covering ...........................................233

10.1 Rib Stitch Spacing .......................................................................... 235

10.2 Rib Stitch Knots .............................................................................. 236

Section 11: Corrosion Detection and Control ...........................239

11.1 Types of Corrosion ......................................................................... 241

11.2 Oxidation ........................................................................................ 243

11.3 Surface and Pitting Corrosion......................................................... 244

11.4 Intergranular Corrosion................................................................... 245 Exfoliation Corrosion .................................................................. 245

11.5 Stress Corrosion ............................................................................. 246

11.6 Galvanic Corrosion ......................................................................... 246

11.7 Concentration Cell Corrosion ......................................................... 247

11.8 Fretting Corrosion ........................................................................... 248

11.9 Filiform Corrosion ........................................................................... 248

11.10 Corrosion Control ........................................................................... 249

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Section 12: Nondestructive Inspection ......................................251

12.1 Visual Inspection ............................................................................ 253 NDI ........................................................................................... 253 Visual Inspection ....................................................................... 253 Surface Visual Inspection ....................................................... 253 Internal Visual Inspection ....................................................... 253

12.2 Tap Test .......................................................................................... 254

12.3 Penetrant Inspection ....................................................................... 255

12.4 Magnetic Particle Inspection .......................................................... 256

12.5 Eddy Current Inspection ................................................................. 257 How it works ............................................................................... 257 What it is suited for ..................................................................... 258 Method ....................................................................................... 258 Detection of corrosion ................................................................ 258

12.6 Ultrasonic Inspection ...................................................................... 259

12.7 Radiography ................................................................................... 259 X-Rays ........................................................................................ 259 Gamma Rays ............................................................................. 260 Inspection—Steps ..................................................................... 260 Considerations ........................................................................... 261 Safety ......................................................................................... 261

Section 13: Aircraft Control Systems ..........................................263

13.1 Types of Control Systems ............................................................... 265 Torque Tubes .............................................................................. 265 Push-Pull Rods ........................................................................... 265

13.2 Control Cables ................................................................................ 266

13.3 Control Cable Terminals ................................................................. 267

13.4 Turnbuckles .................................................................................... 268 Turnbuckle Safetying .................................................................. 268 Clip-Locking Turnbuckles ............................................................ 269

13.5 Control Cable Tension .................................................................... 270

Section 14: Aircraft Fluid Lines .....................................................273

14.1 Rigid Fluid Lines ............................................................................. 275 Materials Recommended for Rigid Fluid Lines ........................... 275

14.2 Flexible Fluid Lines ......................................................................... 277 Types of Flexible Fluid Lines ...................................................... 277

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14.3 Installation of Flexible Hose ............................................................ 279

14.4 Fluid Line Identification ................................................................... 280

Section 15: Oxygen System Servicing ........................................283

15.1 Oxygen System Servicing .............................................................. 285 Filling Pressure for 1,850 PSI Oxygen Cylinders ....................... 285

Section 16: Aircraft Weight and Balance ...................................287

16.1 Locating the Center of Gravity ........................................................ 289

16.2 Datum Forward of the Airplane—Nose Wheel Landing Gear ........ 290

16.3 Datum Aft of the Main Wheels — Nose Wheel Landing Gear ......... 291

16.4 Datum Forward of the Main Wheels —Tail Wheel Landing Gear .... 292

16.5 Datum Aft of the Main Wheels —Tail Wheel Landing Gear ............ 293

16.6 Location of CG with Respect to the Mean Aerodynamic Chord ..... 294

Section 17: Composites ...................................................................297

17.1 Resin Systems—Typical Properties ............................................. 299

17.2 Resin Mix Ratios ........................................................................... 300

17.3 Fiber/Resin Ratio Formulas .......................................................... 301

17.4 Reinforcing Fibers .......................................................................... 302

17.5 Textile and Fiber Terminology ......................................................... 303

17.6 Yarn Part Numbering Systems ....................................................... 304

17.7 Fabric Weave Styles ...................................................................... 305

17.8 Common Weave Style Numbers and Features .............................. 307

17.9 Ply Orientation Conventions ........................................................... 308

17.10 Damage Removal—Scarfing and Stepping ................................... 308

17.11 Core Materials ............................................................................... 310

17.12 Bleeder Schedules ......................................................................... 311

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Appendices ..........................................................................................313

Appendix 1 Hydraulic Fittings ................................................................ 315

Appendix 2 Engines .............................................................................. 319

Appendix 3 Lead Acid Aircraft Batteries ................................................ 321

Appendix 4 Michelin Aircraft Tires ......................................................... 349

Index ......................................................................................................369

Appendix 4: Michelin Aircraft Tires 349

Courtesy Michelin Aircraft Tire

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Appendix 4: Michelin Aircraft Tires

Aircraft Tire Construction 351

Radial-Specific 353

Safety 354

Tire Care Basics 356

Mounting 357

On-Aircraft Tire Inspection 361

Wear 362

Limits for Tire Damages 364

Dismounting 366

Understanding Regulatory Requirements 368



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Aircraft Tire Construction

TreadThe term “tread” refers to the area of the tire that is actually in contact with the ground. Also referred to as the “crown” area, the tread of most Michelin® aircraft tires contain circumferential grooves molded into the tire in the tread area. These grooves are designed to channel water from between the tire and the runway surface thereby improving ground traction on wet runways.

UndertreadThe term “undertread” refers to a layer of specially formulated rubber designed to enhance the bonding between the carcass body and the tread reinforcing plies in bias tires or the protector plies in radial tires.

Carcass PlyA carcass ply consists of fabric cords (most often nylon), sandwiched between two layers of rubber. The carcass body itself is made from multiple layers of carcass plies, each adding to the strength and load bearing capacity of the tire. The carcass plies are anchored by wrapping them around bead wires, thus forming the ply turn-ups.

BeadThe bead, composed of a number of bead wires, anchor the tire to the wheel. They are made from steel wires that are layered together and embedded

Bias tire construction

Tread

Tread reinforcing ply

Undertread

Sidewall

Carcass plies

Carcass ply turn-ups

Liner

Bead

Chafer strips

352 Aviation Mechanics Handbook


in rubber to form a bundle. This bundle is then wrapped with rubber coated fabric for reinforcement. Generally, bias tires are made with 2–6 bead bundles (1–3 per side) whereas radial tires have 2 bead bundles (1 per side) regardless of the tire size.

Chafer StripsStrips of protective fabric or rubber laid over the outer carcass plies in the bead area of the tire. The purpose of these strips is to protect the carcass plies from damage when mounting or demounting the tire and to reduce the effects of wear and chafing between the wheel and the tire bead.

LinerIn a tubeless tire, this is a layer of rubber specially compounded to resist the permeation of nitrogen and moisture through to the carcass. It is vulcanized to the inside of the tire and extends from bead to bead. On a tubeless tire, the liner replaces the inner tube. With a tube-type tire, a different, thinner liner material is used to protect the carcass plies from moisture and the tube from chafing. The liner of a tube-type tire is generally insufficient for air retention.

SidewallThis is a layer of rubber covering the outside of the carcass plies. It protects the cord plies and contains anti-oxidants. These chemicals are slowly released over time to help protect the tire from UV and ozone damage.

The following terms are specific to bias-ply tires:Definition of “Bias”Bias ply tires are constructed with the carcass plies laid at angles between 30° and 60° to the centerline or rotation direction of the tire. The succeeding plies are laid with the cord at angles that are opposite to each other. This provides balanced carcass strength. Most aircraft tires in service today are bias ply tires.

Tread Reinforcing PlyThis consists of single or multiple layers of a special nylon fabric and rubber laid midway beneath the tread grooves and top carcass ply. These plies help to strengthen and stabilize the crown area by reducing tread distortion under load. Additionally, the tread reinforcing ply increases high speed stability and offers added resistance to tread puncture and cutting.

Breaker PliesThese are sometimes used to reinforce the carcass in the tread area of the tire.



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New Bias Technology (NBTTM)This is a technology developed by Michelin that is unique to the construction of some of the Michelin® bias tires. It consists of a crown reinforcement placed on the inside of the tire. This reinforcement strengthens and provides a more uniform pressure distribution in the footprint of the tire. This slows the rate of wear and improves the landing performance of a tire with a lighter weight design.

Radial-Specific

Definition of “Radial”Radial tires are constructed with each carcass ply laid at an angle that is approximately 90° to the centerline of rotational direction of the tire. Each successive layer is laid at a similar angle. Radial tires have fewer plies than bias tires of the same size because the cord direction is aligned with the burst pressure radial force, allowing for optimized construction.

Protector PlyThis is typically found in retreadable tires in the crown area just under the tread rubber. It provides cut resistance to the underlying belts and carcass plies.

New Bias Technology (NBT TM)



Belt PliesThese are laid between the tread area and the top carcass ply. The purpose is to restrain the outer diameter of the tire thereby providing a tread surface with greater resistance to squirm and wear. It also provides a more uniform pressure distribution in the footprint for improved landing performance.

ChineThe chine tire is a nose wheel specially designed to deflect water and slush to the side and away from aft-fuselage mounted engines.

Safety

Aircraft tire and wheel assemblies must operate under high pressures in order to support the loads placed on them. Consequently they should be treated with respect and regard for the high-pressure nature of the assembly. Follow the recommendations outlined in this Michelin Aircraft Tire care and service guide, as well as those guidelines, recommendations and regulations provided by industry authorities such as wheel manufacturers, airframe manufacturers and governmental agencies.

Tread

Protector ply

Undertread

Belt plies

Sidewall

Carcass plies

Carcass ply turn-ups

Liner

Bead

Flipper strip

Radial tire construction



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Later in this tire guide, you will learn about considerations when mounting aircraft tires. When you are doing this type of work there are two basic safety concerns to remember in addition to the mounting information found later in this guide:

• Inordertoavoidbackpainandotherlifting-relatedinjuries,alwaysrolltires on the floor rather than carrying the tire. And always use mechanical lifting tools rather than picking the tire up. Aircraft tires and wheel assemblies are often heavy and represent a potential for injury if not handled properly.

• Beforemountinganytire,visuallycheckthetireandthewheelfordamagethat may have occurred in shipping or even during the time that the tire was stored in your facility.

Important: In the event of a conflict between recommended procedures, be sure to contact your Michelin representative before undertaking the procedure in question.

After a tire has been mounted it will need to be inflated. It is important to respect the recommended inflation pressures and all other safety recommendations during the process of inflation. Most aircraft tires rated for over 190 MPH are inflated with nitrogen.

• Wheninflatingtires,besuretouseasuitableinflationcage.

• Keeppressurehoseandfittingsusedforinflationingoodcondition.

• Allowthetiretoremainintheinflationcageforseveralminutesafterreaching its full inflation pressure.

In service, tires should also be treated with care so as to avoid conditions that would damage the tire and wheel assembly or create a dangerous situation for those around the assembly or aircraft.

• Carefulattentionshouldbeshowntotireandwheelassembliesthatarebeing handled or that are in storage. The Storage section on the next page will give you more details on proper storage.

• Youshouldneverapproach,orallowanyoneelsetoapproach,atireandwheel assembly mounted on an aircraft that has obvious damage until that assembly has been allowed to cool to ambient temperature. This cooling generally requires at least three hours.

• Alwaysapproachatireandwheelassemblyfromanobliqueangle,inthedirection of the tire’s shoulder.



• Deflatetiresbeforeremovingtheassemblyfromtheaircraftunlessitwillbeimmediately remounted (for example, in the case of a brake inspection).

• Alwaysdeflatethetiresbeforeattemptingtodismountthetirefromthewheel or disassembling any wheel component.

• Useextremecautionwhenremovingvalvecoresastheycanbepropelledfrom the valve stem at a high rate of speed.

• Whentireandwheelassembliesarefoundwithoneormoretieboltnutsdamaged or missing, remove the assembly from service.

• Transportingserviceabletireandwheelassembliesmustbedoneinaccordance with the applicable regulatory body for the airline. The transportation of a serviceable inflated aircraft tire is covered by the U.S. Department of Transportation Code of Federal Regulations, the International Air Transport Association (IATA) and other regulatory bodies.

• Whileserviceabletiresmaybeshippedfullypressurizedinthecargoareaof an aircraft, it is Michelin’s preference to reduce pressure to 25% of the operating pressure or 3 bars/40 psi, whichever is less.

Tire Care Basics

StorageAircraft tires and tubes should always be stored in a dry dark environment, free from sunlight and ozone producing appliances such as air compressors. Aircraft tires do

Recommended approach angle

Tires should be stored vertically in racks



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not have a specific shelf life and can successfully be stored for long periods of time, if proper techniques are used. Try to avoid florescent lighting and mercury vapor lights as they generate ozone. Tires should always be stored vertically, on their tread. Stacking tires on their sidewall can cause the beads to collapse, making the mounting process difficult.

Inflation PressureThe most important service you can perform on your aircraft’s tires is to make sure they are properly inflated at all times. If you make one or more flights a day, tire pressure should be checked daily. Tire pressure should be checked on the tires before the first flight of the day. If you fly less than one time per day, you should check tire pressure before each flight. Whether using tube-type or tubeless tires, the operating pressures should be set following the instructions given by the airframe manufacturer.

Properly Inflating Tube-Type TiresAir is usually trapped between the tire and the tube during mounting. Although initial readings show proper pressure, the trapped air will seep out around the valve stem hole in the wheel, and under the tire beads. Within a few days, as the tube expands to fill the void left by the trapped air, the tire may become severely underinflated. To compensate for this effect, check tire pressure before each flight for several days after installation, adjusting as necessary, until the tire maintains proper pressure.

Tire GrowthDuring the first 12 hours after mounting and initial inflation, aircraft tires will generally grow between 6–10%. This is due to the stretching of the nylon plies that make up the internal structure of the tire. This growth will cause the inflation pressure of the tire to drop 6–10% as well. This is entirely normal, and is accounted for during mounting procedures.

Mounting

WheelsMake sure you are familiar with and inspect all key wheel parts before beginning to mount a tire. To assist in this process, wheel manufacturers publish specific instructions in their maintenance manuals. Follow their recommendations and procedures for wheel assembly and disassembly to help obtain trouble-free mounting and dismounting.



Special care should be given to the following:

• Ensurethatthebeadseatingareaofthewheelisclean.

• Matingsurfacesofthewheelhalvesshouldbefreeofnicks,burrs,smalldents, or other damage. Painted or coated surfaces should be in good condition.

• Besurefuseplugs,inflationvalves,andwheelplugsareingoodconditionand properly sealed against pressure loss.

• O-ringgroovesinthewheelhalvesshouldbecheckedfordamageordebris.

• O-ringsmustbeofthepropermaterial.

TiresBefore mounting any tire, check that the tire markings are correct for the required application (size, ply rating, speed rating, part number, and TSO marking).

Visually inspect the outside of the tire for:

• Damagecausedbyimpropershippingorhandling.

• Cuts,tears,orotherforeignobjectspenetratingtherubber.

• Permanentdeformations.

Wheel half and O-ring



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• Debrisorcutsonthebeadseatingsurfaces.

• Beaddistortions.

• Crackingthatreachesthecords.

• Contaminationfromforeignsubstances(oil,grease,brakefluid,etc.)which can cause surface damage.

Inspect the inside of the tire for:

• Foreignmaterial.

• Wrinklesintheinnerliner.

• Innerlinerdamage.

Initial Pressure Retention CheckThe initial pressure retention check requires approximately 15 hours to determine if an assembly can be accepted for service. This important process helps assure reliable service and avoid costly returns for repairs. Additional checks are performed on tire/wheel assemblies not meeting the minimum acceptance criteria for pressure loss.

The procedure is as follows:

1. Inflate the newly mounted tire/wheel assembly to operating pressure as specified.

2. Store the inflated assembly for 3 hours.

3. Check the inflation pressure (be sure that the ambient temperature has not changed more than 5°F—a drop of 5°F will reduce inflation pressure by 1%).

a. If the inflation pressure is ≥ 90% of the operating pressure, go to step 4. If the inflation pressure is ≤ 90% of the operating pressure, inspect the assembly for leakage. Use a soap solution on tire beads, valves, fuse plugs, etc.

b. If soap bubbles or leaks are found, make appropriate repairs and return to step 1.

4. Re-inflate the tire to the specified operating pressure.

5. After a 12 hour storage period, check the inflation pressure (once again be sure the ambient temperature has not changed more than 5°F).

a. If the inflation pressure is ≥ 97.5% of the operating pressure, re-inflate the tire to the specified operating pressure and accept the tire/wheel assembly. Stop initial pressure retention check.

b. If the inflation pressure is ≤ 97.5% of the operating pressure, inspect the assembly for leakage as in step 3b and proceed to step 6.



6. Re-inflate the tire to the specified operating pressure.

7. After a 24 hour storage period, check inflation pressure (be sure the ambient temperature has not changed more than 5°F).

a. If inflation pressure is ≥ 95% of the operating pressure, re-inflate the tire to the specified operating pressure and accept the tire/wheel assembly. Stop initial pressure retention check.

b. If inflation pressure is ≤ 95% of the operating pressure, reject the tire/ wheel assembly.

Aircraft tire/wheel assembly



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On-Aircraft Tire Inspection

Inflation PressureTo help avoid false readings, tire pressure should be checked on tires before the first flight of the day. If this is not possible, wait at least 3 hours after landing to allow the tire to cool to ambient temperature. Air in a hot tire will expand, causing a temporary higher pressure reading. Never bleed pressure from a hot tire.

Effects of UnderinflationToo little pressure can be harmful to your tires and dangerous to your aircraft and those in it. Underinflated tires can creep or slip on the wheel under stress or when brakes are applied. Valve stems can be damaged or sheared off and the tire, tube or complete wheel assembly can be damaged or destroyed. Excessive shoulder wear may also be seen. Underinflation can allow the sidewalls of the tire to be crushed, causing bead damage and making the tire unsafe to use. Severe underinflation may cause ply separation and carcass degradation. This same condition can cause inner tube chafing and a resultant blowout.

Effects of OverinflationTires operating under too much inflation pressure are more susceptible to bruising, cuts, and shock damage. Ride quality as well as traction will be reduced. Continuous high pressure operation will result in poor tire wear and reduced landings. Extremely high inflation pressures may cause the aircraft wheel or tire to explode or burst, which may result in serious or fatal injuries. Never operate aircraft tires above rated inflation pressure.

Checking tire pressure



Wear

Removal CriteriaIn the absence of specific instructions from the airframe manufacturer, a tire should be removed from service for wear using the following criteria. Based on the fastest wearing location, remove tires:

• Whenthewearlevelreachesthebottomofanygroovealongmorethan1/8 of the circumference on any part of the tread, or

• Ifeithertheprotectorply(radial)orthereinforcingply(bias)isexposedformore than 1/8 of the circumference at a given location.

note: If an aircraft has made an emergency or particularly rough landing, the tire, tube and wheel should always be checked.

OverinflationOperating a tire at a higher pressure than required will cause increased wear at the center of the tread. This will reduce the life of the tire and make the tire more susceptible to bruises, cutting, and shock damage.

UnderflationWhen a tire is consistently operated underinflated, shoulder wear will result. Severe underinflation may cause ply separations and carcass heat build-up, which can lead to thrown treads, sidewall fatigue, and shortened tire life.

Worn Beyond Recommended LimitsIf a tire is worn into the carcass/body plies, the strength of the tire will be reduced. This may cause the tire to burst or explode, which may result in serious or fatal injuries.

Flat SpottingThis wear condition is a result of the tire skidding without rotating, and is usually caused by brake lock-up or a large steer angle. The tire should be removed from service if the flat spotting exposes the protector or reinforcing ply, otherwise the tire may remain in service if it does not cause aircraft vibration.

Asymmetrical WearThis is a result of the tire operating under prolonged yaw and/or camber. Tires that do not expose any fabric can be dismounted, turned around, and remounted to even up wear.



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Belt PliesCasing Outer PlyProtector Ply

Tread Reinforcing PliesCasing Outer Ply

Bias

Radial

Overinflation

Bias

Underinflation



Radial

Worn beyondrecommended

limits


BiasFlat spotting Tread Reinforcing Plies

Casing Outer Ply

Radial

Asymmetricalwear


Common tire wear conditions



BA C

D E

A. BulgeB. Chevron cuttingC. Tread chipping/chunkingD. Peeled ribE. Cracking and contamination

Common damage conditions

Limits for Tire Damages

Tread Cuts/Foreign ObjectsIn the absence of specific cut removal instructions from the airframer, tires should be removed when:

• Cuts,embeddedobjects,or other injuries expose or penetrate the carcass plies (bias) or tread belt layers (radial).

• Acutorinjuryseversorextends across a tread rib.

• Undercuttingoccursatthebase of any tread rib cut.

• Roundforeignobjectopenings are acceptable up to .375" in diameter.

Bulges or SeparationsImmediately remove the tire from service. Mark these areas with a color crayon before deflating.

Chevron CuttingRemove from service if the chevron cutting results in chunking which extends to and exposes the reinforcing or protector ply more than one square inch.

B

B

A

A

C

C

Bias

Radial

Remove tire from service when:A. Depth of cut exposes the casing outer ply (bias) or outer belt layer (radial).B. A tread rib has been severed.C. Undercutting occurs at the base of any cut.



Remove tire from service when: A. Depth of cut exposes the casing outer

ply (bias) or outer belt layer (radial).B. A tread rib has been severed.C. Undercutting occurs at the base of

any cut.



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Chevron cutting is caused by the sharp-edged ridges of concrete on runways which have been crosscut.

Tread Chipping/ChunkingRemove from service if the reinforcing ply or protector ply is exposed for more than one square inch.

Peeled RibRemove from service if the reinforcing ply or protector ply is exposed.

Groove CrackingRemove from service if the groove cracking exposes the reinforcing ply of protector ply for more than 1/4" in length. An aircraft may return to a maintenance base to replace tires meeting this condition if there is no continuous cracking exposing fabric greater than one inch in length.

Rib UndercuttingRemove from service if undercutting extends more than 1/4" under the rib.

Contamination From HydrocarbonsOil, grease, brake fluids, solvents, etc., can soften or deteriorate rubber components. If a tire comes in contact with any of these, immediately

Protect tires from contaminants



wash the contaminated area with denatured alcohol, then with a soap and water solution. If the contaminated area is soft and spongy compared to an unaffected area of the tire, remove the tire from service.

Sidewall CutsIf sidewall cords are exposed or damaged, remove the tire from service. Cuts in the rubber which do not reach the cord plies are not detrimental to tire performance—the tire may remain in service.

Weather/Ozone CrackingRemove from service only if weather or ozone cracks extend to the cord plies.

Dismounting

Proper dismounting procedures simplify the job of servicing aircraft tires, while increasing safety and reducing the chances of damaging tires or wheels. The task of dismounting tires should not be undertaken without proper equipment, instructions, and trained personnel. The following is the basic sequence that should be followed:

• Beforebeginninganytiredismount,besuretofollowtheinstructionsandprecautions published in the wheel supplier’s maintenance manual.

• Markdamagedorbulgeareas,ifany,beforedeflating,usingacontrastingcolor chalk.

• Completelydeflatethetireortubebeforedismounting.

• Useabeadbreakertoloosentirebeadsfrombothwheel-halfflanges.

• Applybeadbreakerrampressureorarmpressureslowly,orinaseriesofsequences or jogs, to allow time for the tire’s beads to slide on the wheel.

What to do if the tire becomes fixed to the wheel:

• Releaserampressure.Applyasoapsolutiontothetire/wheelinterface.

• Allowseveralminutesforthesolutiontopenetratebetweenthetireandwheel.

• Reapplyareducedhydraulicpressuretothetire.

• Repeatseveraltimesifnecessary.



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1

2

3

4

If the tire still remains fast:

• Removethetire/wheelassemblyfromthemachine.

• Reinflatethetireinacageuntilthebeadmovesbacktoitscorrectposition.

• Deflatethetire.

Recommence the dismounting procedure:

• Removetieboltsandslideoutbothpartsofthewheelfromthetire.

• Fortube-typetires,removethetube.

• Tireisnowdismounted.

Off-Aircraft Inspection with Tire DismountedA systematic approach to tire inspection is recommended to ensure that all areas are properly inspected. The following system is recommended:

• Inspectthetreadarea—followtheprocedures for on-aircraft inspections.

• Inspectbothsidewallareas—follow the procedures for on-aircraft inspections.

• Inspectthebeadareas—check the entire bead area for chafing or damage.

• Inspecttheinnerliner— any tire with loose, frayed or broken cords or wrinkles should be discarded. Liner blisters, especially in tubeless tires, should be left undisturbed.

• Inspecttheinnertube,ifapplicable—tubes with leaks, severe wrinkles or creases, or chafing should be properly discarded.

• Inspectforwheeldamage—wheelsshould be inspected according to the wheel manufacturer’s recommendations.

Vibration and BalanceVibration, shimmy, and other similar conditions are usually blamed on improper tire balance. Imbalance is a well known and easily understood

Suggested approach: 1. Tread; 2. Sidewalls; 3. Bead areas; 4. Innerliner



cause for vibration. In many cases, though, this may not be the cause. There are a number of specific aspects of the tire, wheel, and gear assembly which can be the cause or contribute to aircraft vibration. As with any concern, a systematic approach should be taken to isolate its cause. The following inspections will help identify and/or prevent this problem:

• Checkthatthetirehasbeeninflatedtotheproperinflationpressure.

• Ensurethatthetirereachesfullgrowthbeforeitisinstalledontheaircraft.

• Checkthatthebeadsofthetirehavebeenproperlyseated.

• Checkthetireforflatspottingorunevenwear.

• Verifythatthetireshavebeenproperlymounted.

• Checkforairtrappedbetweenthetireandtube.

• Checkforwrinklesinthetube.

• Checkthewheelforanimbalanceduetoimproperassembly.

• Checktheconditionofthewheeltoseeifithasbeenbent.

• Checkforaloosewheelbearingcausedbyanimproperlytorquedaxlenut.

• Checkforpoorgearalignmentasevidencedbyunevenwear.

• Checkforwornorlooselandinggearcomponents.

Understanding Regulatory Requirements

FAA Certification/New TiresThis certification requires qualification of the tire to FAA Technical Standard Order (TSO) C62d. Generic static and dynamic tests are determined based upon the speed and load rating of the tire, and may include numerous landing, taxi, and take-off cycle tests.

FAA Certification/Retreaded TiresTires are qualified to the requirements of FAA Advisory Circular 145-4. Tires are tested based upon the speed rating and current retread level.

OEM CertificationThis certification is generally based on aircraft specific requirements, as required by the OEM, in addition to FAA certification per TSO-C62d.

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