Aviation Maintenance 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.
Dynamometer Cycles
The test tire is required to withstand 50 takeoff cycles, and 8 taxi cycles as described below. The sequence of the cycles is optional.
Flatspotting
A localized accelerated wear condition associated with landings; 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 Damage (FOD)
Material that, if left on the runway, taxiway, or ramp, that could cause damage to tires, engines, or other aircraft structures; Damage resulting from contact with foreign objects.
High Speed Tires
Tires operated in speed ranges of above 120 mph under TSO-C62c and above 160 mph under TSO-C62b.
Innerliner
The integral rubber lining of a tubeless tire that is engineered to prevent the diffusion of the inflation gas into the casing.
Innertube
A gas-tight rubber device placed inside a tube-type tire casing for the purpose of containing the inflation gas. It is provided with an integral valve assembly.
Loaded Radius
The distance from the axle centerline to a flat surface for a tire initially inflated to the rated inflation pressure and then loaded to its rated load against the flat surface.
Nominal Loaded Radius
The allowable tolerance on the loaded radius, and the actual load radius for the test tires should be identified.
Overpressure
The tire is required to withstand, for at least 3 seconds without rupture, a minimum test inflation pressure of at least 3.0 times the rated inflation pressure at ambient temperature.
Process Specifications
Documents approved by the Administrator containing information for performing specialized maintenance, such as specifications. Air carriers or conmercial operators having a continuous airworthiness maintenance program under FAR Parts 121, 127, or 135, are required to include a process specification for retreading their tires in their program. Part 125 operators have inspection programs that require each operator to include a process specification in its manual for retreading its tires.
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.
Recap and Recapping
Synonymous with the terms retread and retreading.
Retread
The methods of restoring a used tire by renewing the tread alone, or by renewing the tread plus one or both sidewalls. It refers as well to the process of extending new sidewall material to cover the bead area of the tire. Repairs are included in the retreading of tires.
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
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.
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.
Takeoff Cycles
For these cycles the loads, speeds, and distance are required to conform to either Figure 1 or Figure 2.
Taxi Cycles
The tire at rated load is required to withstand at least 8 taxi cycles on a dynamometer for a minimum speed of 40 mph and a minimum roll distance of 35,000 feet.
Test Inflation Pressure
The pressure required at an identified ambient temperature to obtain the same loaded radius against the flywheel of the dynamometer as the radius for flat surface as defined in paragraph 7c (2) of this AC. Adjustment to the test inflation pressure may not be made to compensate for increases due to temperature rise Occurring during the tests.
Testing
Tires operating at ground speeds greater than 160 mph are required to be tested on a dynamometer. Tires operating at ground speeds of 160 mph or less may, as an option, be tested on the dynamometer in accordance with paragraph 7c (7)(111).
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
Indicating System (Installed on an Aircraft) A system installed on an aircraft used for tire pressure checks.
Tire Test Load
The tire is required to be forced against the dynamometer flywheel at not less than the rated load of the tire during the entire roll distance of the test.
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.
Restrict the list to specific handbooks by clicking on the menubar at the top of the screen.