Aircraft Tyres fall into two disticnt technologies - bias (also known as cross ply) and radial. Bias and radial tyres are significantly different to each other and both technologies offer operators features and benefits that might be considered agreeable for particular applications. The aircraft tyre is a composite structure of three basic materials:
The components are bonded together by vulcanisation.
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Much of the tyre terminology is common to radial and bias tyres - each type has unique components reflecting the different technologies applied to design, compounds and materials.
The bias ply tyre, (click for larger image and labels) shown in the first picture consists of casing plies running diagonally at approximate right angles to one another. The number of plies and the angles at which they are laid dictate strength and load capacity. The latest high-performance bias ply aircraft tyres feature inter-tread reinforcing fabric (ITF). This provides additional high-speed stability, reduces tread distortion under load, protects the casing plies from damage and can act as wear indicators on retreadable tyres. Bias Tyres are currently the most popular tyres fitted to the worlds fleet.
Radial aircraft tyres, shown in the second picture (click for larger image and labels), differ to bias aircraft tyres in that the plies all run radially from bead to bead at approximately 90° to the centre-line of the tyre. Angled belt plies are laid between the tread and the top casing ply, resulting in a flatter tread and adding strength to the tyre.
Radial tyres can offer low weight but tend to be less retreadable than a bias ply tyre and can exhibit weaker sidewalls.
A specially compounded rubber formulated to resist wear, cutting, chunking and heat build up. Most Dunlop aircraft tyre designs feature circumferential grooves moulded into the tread to disperse water from beneath the tread in wet runway conditions.
The tread helps to reduce the risk of aqua planing and improves traction and grip between the tread and runway surface.
The basic strength of the tyre is provided by the casing plies. Casing plies are layers of fabric cord coated with hi-modulus rubber on both sides. Casing plies are held in place by being wrapped around the beads to provide the casing ply turn up.
The bead wire anchors the tyre to the rim and ensure an airtight seal.
Beads consist of bundles of high-tensile steel wires, each strand of which is coated in rubber compound and wound into coils of the correct diameter for a given tyre size.
Chafers are made of tough nylon material and are fitted around the bead clinch area to resist chafing damage to both tyre and rim flange.
The area of the tyre between the shoulder and the bead. The sidewalls are covered with a layer of specially formulated rubber treated with anti-oxidants. The sidewall protects the casing plies from the effects of weathering and offers resistance to cuts and flexing.
Tubeless tyres have a layer of rubber bonded to the inside of the first casing ply from bead to bead to resist the permeation of nitrogen and moisture into the casing.
The undertread is a layer of rubber that is designed to improve the adhesion between tread/ ITF and the casing plies. During the retreading process, the layer acts as the interface for the application of fresh tread rubber.