Learning Objective: Recognize the proce-dures for dismounting, mounting, and inflating aircraft tires. You should be able to identify various tire markings and determine preventive maintenance requirements indicated by tire tread wear.

Proper care and maintenance of tires have always been important items in aircraft maintenance.

Because of the modern fast-landing aircraft, careful tire maintenance has become increasingly important. Aircraft tires are built to withstand a great deal of punishment, but only by proper care and maintenance can they give safe and dependable service.

These designations refer to construction features and the types of tire casings with which they are used. The dimensions used to identify wheels are not necessarily the dimensions of the wheels themselves. Instead, they refer to dimensions of the tire. Tire size designations are discussed later.

Figure 11-10 shows the construction details of a tube-type aircraft tire. Tubeless tires are similar to tube tires except they have a rubber inner liner that is mated to the inside surface of the tire. The rubber liner helps retain air in the tire. The beaded area of a tubeless tire is designed to form a seal with the wheel flange. Wear indicators have been built into some tires as an aid in measuring tread wear. These indicators are holes in the tread area or lands in the bottom of the tread grooves.

The cord body consists of multiple layers of nylon with individual cords arranged parallel to each other and completely encased in rubber. The cord fabric has its strength in only one direction. Each layer of coated fabric constitutes one ply of the cord body. Adjacent cord plies in the body are assembled with the cords crossing at nearly right angles to each other. This arrangement provides a strong and flexible tire that distributes impact shocks over a wide area. The functions of the cord body are to give the tire tensile strength, to resist internal pressures, and to maintain tire shape.

The tread is a layer of rubber on the outer surface of the tire. It protects the cord body from abrasion, cuts, bruises, and moisture. It is the surface that contacts the ground.

Figure 11-10.Sectional view of aircraft tire showing construction details.

The sidewall is an outer layer of rubber adjoining the tread and extending to the beads. Like the tread, it protects the cord body from abrasion, cuts, bruises, and moisture.

The beads are multiple strands of high-tensile strength steel wire imbedded in robber and wrapped in strips of open weave fabric. The beads hold the tire firmly on the rims and serve as an anchor for the fabric plies that are turned up around the bead wires. The chafing strips are one or more plies of rubber-impregnated woven fabric wrapped around the outside of the beads. They provide additional rigidity to the bead and prevent the metal wheel rim from chafing the tire. Tubeless tires have an additional ply of rubber over the chafing strips to function as an air seal.

The breakers are one or more plies of cord or woven fabric impregnated with rubber. They are used between the tread rubber and the cord body to provide extra reinforcement to prevent bruise damage to the tire. Breakers are not part of the cord body.