Aircraft Tires | Aircraft Tires Design, Construction and Maintenance

Aircraft Tires

Aircraft Tires are very important parts for the smooth operation of an aircraft. When an aeroplane is on the ground, its weight is supported by its tyres, which also enable simple movement while rolling and provide the necessary traction for braking and halting. These tires also help absorb the shock of landing and cushion the roughness of takeoff, rollout, and taxi operations. Aircraft tires must be carefully maintained to perform as required. These tires accept a variety of static and dynamic stresses and must do so reliably in a wide range of operating conditions. Aircraft tires can be tubes types or be tubeless.

As an alternative to natural rubber, buna-S rubber is typically used for tires and tubes.

Tire Classification

There are several different methods to categorise aircraft tires, including type, ply rating, tube type or tubeless, and bias ply or radial. Another method of identifying tires is by their measurements. The discussion of each of these categories is as follows.


The United States Tire and Rim Association's classification of aircraft tires by type is a typical classification system. There are nine different types of tires, however only the Three-Part Nomenclature tires, or Types I, III, VII, and VIII, are still manufactured.

Although Type I tires are still produced, its design is no longer in use. They are only identified by their nominal overall diameter in inches and are used on fixed-gear aircraft. These tires have a smooth profile and are no longer suitable for use in the fleet of contemporary aircraft. On older aircraft, you might find these.

Common tires for general aviation are Type III tires. They are frequently utilised on small aircraft with landing speeds of no more than 160 mph. When compared to the entire width of the tire, Type III tires have modest rim diameters and relatively low pressure. They have a rather broad footprint yet are made to cushion and offer float. Two numbers are used to identify Type III tires. The first number represents the tire's nominal section width, while the second is the rim diameter that the tire is intended to mount to.

High performance Type VII tires are typically found in jet aircraft. They have an unusually high load carrying capacity and are inflated to high pressure. Type VII tires typically have a narrower section width than Type III tires. A two-number system is used for Type VII aeroplane tire identification. Between the two digits is an X. The tire's nominal overall diameter is indicated by the first digit. The section width is indicated by the second digit.

Three-part nomenclature tires are another name for Type VIII aeroplane tires. They are employed on high-performance jet aircraft and inflated to extremely high pressure. The average Type VIII tire has a low profile and can withstand weights and speeds that are extremely high. Of all tire kinds, it has the most contemporary design. The total tire diameter, section width, and rim diameter are used to identify the tire in the three-part nomenclature, which combines Type III and Type VII nomenclature. The designator uses the X and "-" symbols in their appropriate places.

Dimensions can be specified on a Type VIII tire with three-part nomenclature in either inches or millimetres. Bias tires use the designation nomenclature, while radial tires use the letter R in place of the "-". A Type VIII radial aviation tire with a 30-inch tire diameter, an 8.8-inch section width, and a 15-inch wheel rim, for instance, is designated as 30 X 8.8 R 15.

There are also a few unique designators for tires used in aircraft. When the identifier is preceded by a B, the tire has a bead taper of 15 degrees and a wheel rim to section width ratio of 60 to 70 percent. The tire has a wheel rim to section width ratio of 60 to 70 percent but only a 5 degree bead taper when a H occurs before the identifier.

Ply Rating

Tire plies are layers of rubber-coated cloth reinforcement that are inserted into tires to add strength. The capacity of early tires was directly correlated with the number of plies utilised. Nowadays, the precise number of plies is less important for estimating the strength of a tire due to improvements in tire production methods and the usage of contemporary materials to produce aircraft tires. To indicate the relative strength of an aviation tire, though, a ply rating is used. No matter how many plies were actually used in its production, a tire with a high ply rating has high strength and can withstand huge weights.

Tube-Type or Tubeless

Aircraft tires can be tube-style or tubeless, as specified. This is frequently used to categorise tires. The inner liner of tires that are intended to be used without a tube put inside of them is especially built to contain air. Since the tube prevents air from leaking out of the tire, tube-type tires do not have this inner liner. Tubeless is written on the sidewall of tires that are designed to be used without a tube. If there is no indication of this, a tube is needed for the tire. For any permitted tire damage and the use of a tube in a tubeless tire, refer to the maintenance guidelines provided by the aircraft manufacturer.

Bias Ply or Radial

The direction of the plies that were utilised to manufacture the tire—bias or radial—can also be used to categorise aeroplane tires. Bias-ply tires are what are typically used on aircraft. To shape and strengthen the tire, the plies are wrapped. Between 30° and 60° is the range of the plies' angle with respect to the direction of rotation of the tire. In this way, the plies are positioned across the tire with the bias of the fabric from which they were made facing the direction of rotation. Thus, they are known as bias tires. As a result of the fabric plies being laid on the bias, the sidewall is flexible.

Radial tires are a type of modern aviation tire. In radial tires, the plies are arranged at a 90° angle to the tire's rotational axis. The non-stretchable fibre of the plies is perpendicular to the sidewall and rotational direction in this design. The tire gains strength as a result, which enables it to carry heavy loads with minimal distortion.

Tire Construction

An aviation tire is built with its intended use in mind. It is not required to bear a load for a lengthy period of time during continuous use, unlike an automobile or truck tire. However, even if only for a brief period of time, an aircraft tire must be able to run at high speeds and be able to withstand the high impact loads of landing. More than twice as much deflection as a vehicle tire is designed into an aeroplane tire. As a result, it can withstand the forces of landings without suffering damage. Use only tires made specifically for aviation, as directed by the manufacturer.

Identification of the various tire parts and how they contribute to the overall characteristics is helpful for understanding tire manufacture.


An aviation tire's bead is an essential component. In addition to providing a dimensioned, secure mounting surface for the tire on the wheel rim, it anchors the tire carcass. Strong tire beads are used. Usually, they are constructed from bundles of high-strength carbon steel wire covered in rubber. Depending on the tire's size and the load it is intended to carry, there may be one, two, or three bead bundles on each side. On each side of a radial tire, there is a single bead bundle. The bead transmits the deflection forces and impact loads to the wheel rim. The bead heel fits against the flange of the wheel rim, and the bead toe is closest to the tire centerline.

To provide a contour for securing the ply turn-ups, additional rubber is moulded into an apex strip and wrapped around the bead. The carcass of the tire is insulated from the beads by layers of fabric and rubber known as flippers, which also increase tire tensile strength. In this region, chafers are also utilised. After the plies have been wrapped around the beads, chafer strips made of fabric or rubber are placed over the outer carcass plies. The chafers shield the tire's carcass from harm when it is mounted and demounted. Additionally, they aid in lessening the impacts of wear and chafing between the tire bead and wheel rim, particularly during dynamic activities.

Carcass Plies

The tire is constructed with carcass plies, also known as casing plies. Each ply is made up of two layers of rubber sandwiching a fabric, typically nylon. To provide the tire strength and create the carcass body of the tire, the plies are applied in layers. The ply turn-ups are formed by wrapping the ends of each ply around the tire's bead on both sides. As previously noted, a bias tire or radial tire can be produced by adjusting the angle of the fibre in the ply. Radial tires often need fewer plies than bias tires.

Bias tires and radial tires each have their own kind of protective layers on top of the plies but beneath the tread of the running surface of the tire once the plies are in place. These single or multiple layers of rubber and nylon used in bias tires are known as tread reinforcement plies. An undertread and a protective ply serve the same purpose on radial tires. These extra plies strengthen and stabilise the tire's crown area. They lessen tread distortion under pressure and improve tire stability at high speeds. Additionally, the protective and reinforcing plies work to keep the tire's carcass body safe from cutting and punctures.


The crown portion of the tire that is intended to make contact with the ground is known as the tread. It is a rubber substance made to withstand tearing, cutting, and breaking. It is designed to withstand heat buildup as well. Circumferential grooves that produce tire ribs are used to form the majority of modern aviation tire tread. In wet weather, the grooves help channel water from under the tire and provide cooling to improve ground adhesion. There may be some sort of cross-tread pattern on tires made for aircraft that are commonly flown from unpaved surfaces. There may be no tread grooves on older aircraft without brakes or with brakes that are solely intended to help with taxi. Some aircraft tires may have an all-weather tread. This tread has the normal circumferential ribs in the tire's centre and a cross tread with a diamond pattern at the tire's edge.

The tread, which is made to stabilise the aircraft on its surface of operation, ages with use. As previously mentioned, protective undertread layers are a common feature of aviation tires. Breakers are sometimes used to provide additional tread reinforcement. Under the tread, there are layers of nylon cord cloth that support the tread while safeguarding the carcass plies. When the tread has worn to the point of no return, tires with reinforced tread are frequently made to be re-treated and used once again. For information on allowable tread wear and re-tread capacity for a certain tire, consult the tire manufacturer's data.


An aviation tire's sidewall is a rubbery covering intended to safeguard the carcass plies. It might include substances made to fend off ozone's damaging effects on tires. Additionally, it is where the tire's information is located. The cable body receives little strength from the tire sidewall. Protection is its primary objective.

The inner liner of a tire protects its inner sidewall. To keep the tube from rubbing against the carcass plies, a thin rubber liner is attached to the inner surface of tube-type tires. The rubber inside of tubeless tires is thicker and less porous. By doing so, the tube is replaced and the nitrogen or inflation air inside the tyre is kept in place, preventing seepage.

Not all of the inflation gas is contained in the inner liner. Small amounts of nitrogen or air enter into the carcass plies through the lining. The vent holes on the lower outer sidewall of the tires are used to let this seepage out. These must be maintained clear and are often identified with a green or white dot of paint. With temperature fluctuations, trapped gas in the plies may expand and separate from one another, weakening the tire and increasing the risk of tire failure. In order to let air trapped between the tube and the tire escape, tube-type tires also have seepage holes drilled into the sidewall.


To create a chine, some tire sidewalls are mounded. A chine is a unique integrated deflector used on the nose wheels of some aircraft, typically those with engines mounted to the fuselage. The chine directs runway water away from the engines' intake and to the side. Image 13-131E For aeroplanes with a single nose wheel, tires featuring chine on both sidewalls are manufactured.

Tire Inspection on the Aircraft

Regularly, the condition of the tires is checked while they are mounted to the aircraft. To guarantee proper tire performance, the following parameters are regularly checked: inflation pressure, tread wear and condition, and sidewall condition.


An aircraft tire needs to be correctly inflated in order to operate as intended. The correct inflation pressure for a tire on a specific aircraft must be determined using maintenance information provided by the aircraft manufacturer. Never plough air into a tire to a pressure indicated on the sidewall or by how the tire appears. The weight of the aircraft on the wheels is used to gauge tire pressure while it is under load. Readings of pressure when loaded and unloaded can differ by as much as 4%. Due to the increased volume of the inflation gas space inside the tire, tire pressure measured with the aircraft on jacks or when the tire is not mounted is lower. This can lead to a 6.4 psi mistake on a tire that should have a 160 psi pressure on it. Always measure inflation pressure with a calibrated pressure gauge. Pressure gauges with a digital or dial display are more reliable and preferable.

Heat is released from aircraft tires during takeoff, taxi, landing, and rollout. Heat builds up as the tire bends and is dissipated into the atmosphere as well as to the rim of the wheel through the tire bead. Braking heats the tire externally as well. Any tire can only withstand a certain amount of heat before suffering structural damage.

An underinflated aircraft tire may experience internal damage that is difficult to see and can cause tire failure. It is always risky when a tire fails upon landing. The purpose of an aircraft tire is to flex and lessen the impact of landing. This causes a rise in temperature. An underinflated tire, however, may bend more than the tire's design allows. As a result, there is an excessive buildup of heat, which undermines the carcass' construction. Tire pressure needs to be checked and kept within the right range every day, or before each trip if the aircraft is only flown seldom, to ensure tire temperature is kept within limits.

At room temperature, tire pressure should be tested. Variations in the surrounding temperature have a significant impact on tire pressure and make it more difficult to maintain pressure within the range required for safe operation. For every 5 °F change in temperature, tire pressure normally changes by 1%. The ambient temperature might vary significantly while an aeroplane is flying between two different environments. The pressure in the tires must be changed appropriately, according to maintenance personnel. For instance, a properly inflated aircraft flying from Phoenix, Arizona, where the temperature is 100 °F, lands in Vail, Colorado, where the temperature is 50 °F. Tire pressure is decreased by 10% for every 50° variation in ambient temperature. Thus, the aircraft might land with underinflated tires that could sustain damage from overheating from bending above design limitations as previously explained. As long as the tires are not inflated above the allowed maximum shown in the maintenance data, increasing tire pressure before takeoff in Phoenix, Arizona, prevents this issue.

After a usual landing, give the tire three hours to cool to room temperature before monitoring the pressure. The manufacturer normally provides a table or graph with the recommended tire pressure for each ambient temperature.

Aircraft tires that are under-inflated not only overheat but also wear unevenly, necessitating early tire replacement. When under stress or when the brakes are engaged, they may also creep or slip on the wheel rim. Extremely low tire pressure can cause sidewall and rim damage by pinching the sidewall between the rim and the runway. Additionally likely are damages to the bottom sidewall area and bead. This kind of abuse, like any excessive flexing, compromises the tire's integrity, necessitating replacement. A tire that is significantly underinflated in a dual-wheel system will impact both tires, thus both need to be replaced.

Another undesirable issue is over-inflated aircraft tires. Although there is no overheating-related carcass damage, adhesion to the landing surface is decreased. Over inflating tires over time causes early tread wear. Overinflation lowers the number of service cycles before the tire needs to be changed. It increases the risk of blowouts, cuts, stress damage, and bruises on the tire. Defender ply Button plies Plies that reinforce the tread Plies that reinforce the tread Case outer ply Case outer ply An overinflated radial tire's tread wear An underinflated radial tire's tread wear An overinflated bias tire's tread wear wear on a bias tire with inadequate air pressure.

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