Aircraft tires key terms describe essential parts that must be designed to withstand a wide range of conditions. They must support the weight of the aircraft on the ground. They need to provide a stable, cushioned ride without generating heat while taxiing. They have to handle not only the aircraft load but also the forces generated at high angular velocities during takeoff. They also have to absorb impact shocks while transmitting high dynamic braking loads to the ground when landing. All of this must be accomplished while also providing a long, dependable service life. Such extreme demands require aircraft tires to be highly engineered and manufactured to precise conditions. Those who work with aircraft tires need a working knowledge of vocabulary directly associated with them.
The tread is the part of the aircraft tire that comes in contact with the ground. It is formulated to resist wear, abrasion, cutting, cracking and heat buildup. Most tread has grooves designed to channel water from between the tire and the runway surface, which improves ground adhesion.
A bias tire, also called a cross ply tire, is made so that the plies are laid at angles between 30 and 60 degrees to the centerline of the tire. Successive plies are laid with angles opposite each other to provide balance and strength.
A radial tire is made so that the plies are laid at an angle approximately 90 degrees to the centerline of the tire. Each successive layer is laid at a similar angle. Radial tires have fewer plies than bias tires because the cord direction provides optimum strength.
Beads, also known as bead wires, are used to connect the aircraft tire to the wheel. They are made from layered steel wires and often are embedded with rubber to form a bundle. Bias tires generally require two to six bead bundles (one to three on each side), depending on the size of the tire; radial tires always have two bead bundles (one on each side) regardless of tire size.
Flat spots are worn areas on the tread of an aircraft tire. The three different types are: skid spots, typically caused by over-breaking and skidding the tire across the runway; skid burns, caused by hydroplaning on water or skidding on ice; and nylon sets, which generally result from parking the aircraft for extended periods of time or in extreme temperatures with a load on the tires.
Retreading is the process of repairing aircraft tires that still have the cord body intact but have treads that are worn out, flat-spotted or otherwise damaged. Retreading aircraft tires saves aircraft operators considerable amounts of money over tire replacement.