Appendix 1
4/18/05 AC 20-97B Appendix 1 APPENDIX 1. GLOSSARY OF TIRE TERMS The following is a list of common tire terms. Glossaries of other tire terms appear in AC 145-4 and in TSO-C62 .
Glossary of Tire Terms Bead Zones that are in contact with the rim areas of the wheel, or the coils of steel wire that provide anchors for the plies.
Bias Tire A pneumatic tire in which the ply cords extend to the beads and are laid at alternate angles substantially less than 90 degrees to the centerline of the tread.
Casing The structural part of a tire.
Deflection The ratio (in percent) of the deflected distance between the rim and tread to the undeflected distance.
Flatspotting A localized accelerated wear condition associated with landings; or A temporary or permanent “out-of-round” condition resulting from a loaded hot tire having not rotated while cooling to the ambient temperature. This condition is most prevalent on bias nylon tires due to the “plastic memory” of the nylon cords.
Foreign Object Material that, if left on the runway, taxiway or ramp, that could cause Damage (FOD) damage to tires, engines, or other aircraft structures; or Damage resulting from contact with foreign objects.
Innerliner The integral rubber lining of a tubeless tire that is engineered to prevent the diffusion of the inflation gas into the casing.
A gas-tight rubber device placed inside a tube-type tire casing for the Innertube purpose of containing the inflation gas. It is provided with an integral valve assembly.
Radial Tire A pneumatic tire in which the ply cords extend to the beads and are laid substantially at 90 degrees to the centerline of the tire. Additional stabilization is provided by essentially inextensible belting in the tread area.
Page 1
Appendix 1
4/18/05 AC 20-97B Appendix 1 Glossary of Tire Terms Safety Cage A reinforced structure that has been specifically designed to protect service personnel from the effects of any explosive event that may occur during the pressurization of a tire/wheel assembly.
Separation Failure of adhesion between components or tearing within a single tire component.
Service Pressure The inflation pressure needed to support the maximum operating load for a wheel position. Service pressure is measured with the assembly under load.
Sidewall Vents Specific perforations in the lower sidewalls of tubeless tires, usually located above the rim centering rib, and defined by paint marks. These perforations release detrimental internal casing pressure.
Sidewall The rubber side area of the tire located between the shoulder and the beads that covers the underlying structure and protects the carcass from damage.
Tire (Pneumatic) A complex engineered structure made of rubber and cord (of textiles or steel) that provide a resilient protective enclosure for the inflating gas.
Tire Pressure A system installe d on an aircraft used for tire pressure checks.
Indicating System (Installed on an Aircraft) Transverse Crack A crack at an angle that is not parallel to the principle direction of the outer ply, breaker, or belt.
Tread The expendable rubber-wearing surface of any pneumatic tire.
It contains the groove pattern designed to facilitate water removal from the contact patch, and may, or may not, possess integral fabric materials.
Tube A gas-tight rubber device placed inside tube-type tire casings for the purpose of containing the inflation gas. It is provided with an integral valve assembly.
Tube - Type Tires Tires requiring tubes for inflation retention.
Tubeless Tires Tires not requiring tubes. These tires are constructed with an innerliner.
Undercutting A rubber fracture that progresses from the tread surface, or in a groove, in a direction parallel to the ply structure.
Page 2 Advisory Circular Feedback Form If you find an error in this AC, have recommendations for improving it, or have suggestions for new items/subjects to be added, you may let us know by contacting the Flight Standards Directives Management Officer at 9-AWA-AF B -1 2 0-Directives@faa.gov .
Subject: AC 20-97B CHG 1, Aircraft Tire Maintenance and Operational Practices Date: _____________________ Please check all appropriate line items: An error (procedural or typographical) has been noted in paragraph ____________ on page _______.
Recommend paragraph _____________ on page __________ be changed as follows: ______________________________________________________________________ ______________________________________________________________________ In a future change to this AC, please cover the following subject: (Briefly describe what you want added.)
______________________________________________________________________ ______________________________________________________________________ Other comments: ______________________________________________________________________ ______________________________________________________________________ I would like to discuss the above. Please contact me.
Submitted by: Date: ______________________