Aircraft Landing Gear systems are intended to support the weight of the aircraft whilst on the ground, enable ground manoeuvres (including the use of nose-wheel steering and brakes) and absorb shock loads caused by take-off, landing and taxiing.
An Aircraft Landing Gear system comprises of many structural like the shock absorber, axle, torque links, side braces, retraction actuators, wheels, and tires as well as the system components (brake system, anti-skid systems, retraction systems, and steering systems).
Aircraft tires (or tyres) are designed to withstand extremely heavy loads for short durations. The number of tires required for aircraft increases with the weight of the aircraft, as the weight of the airplane needs to be distributed more evenly. Aircraft tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, as well as for braking function.
Bias and radial aircraft tires and matching tire tubes are offered as part of our own labelled (AVIATION NEW ERA) product lines for use in main and nose wheel applications in general aviation, commercial, military aircraft and other projects.
Sourced from co-operating quality manufacturers holding ISO and other certifications, the AVIATION NEW ERA tires are available in Tube-type or Tubeless types in different ply ratings, tread patterns and sizes to meet respective rated load and pressure requirements of intended applications. For tube type tires, matching tire tubes with straight or bent valves are also offered. The AVIATIONEU NEW ERA aircraft tires and tubes are intended as cost-effective alternate parts to the respective known brands.
They are approved for use on the respective aircraft in their country of origin and/or other countries where they are exported.
Our brief guide below on aircraft tires is intended to assist in your better understanding of their classification, construction and characteristics. Please contact us for more information.
Classification of aircraft tires is commonly based on their type, dimensions, ply rating, whether they are tube-type or tubeless, and whether they are bias ply tires or radials.
Aircraft Tires Types
There are nine types of tires in total but only Types I, III, VII, and VIII are still in production. Type I tires are smooth profile tires used on fixed gear aircraft and are designated only by their nominal overall diameter in inches. Type III tires are common general aviation tires, generally used in low pressure service operations and typically used on light aircraft with landing speeds of 160 miles per hour (mph) or less. They are designated with a two number system (N - D). The first number (N) is the nominal section width of the tire, and the second number (D) is the rim diameter the tire is designed to mount upon. Type VII tires are high performance tires found on jet aircraft. They are inflated to high-pressure and have exceptional high load carrying capability. Identified by a two-number system (M X N ), the first designating the nominal overall tire diameter and the second the nominal section width with an "X" between the two numbers. Type VIII aircraft tires are inflated to very high-pressure, used on high-performance jet aircraft and are capable of operating at very high speeds and very high loads. Also known as Three-Part Nomenclature tires,Type VIII aircraft tires use nominal overall tire diameter, nominal section width and rim diameter as part of their identification nomenclature with "X" and “–” symbols used in the designator as follows:
M X N - D or M X N R D
"M" indicates the nominal overall tire diameter
"N" indicates the nominal section width
"D" indicates the rim diameter
In INCH code tires designators M, N & D are in inches.
In METRIC code tires designators M, N are in millimeters & D is in inches.
The "-" and "R" are sometimes referred to as the construction code. These tires are designed for high speed/high load aircraft.
Sometimes tire designators are preceded by the letters "B", "H" or "C". These are special designators used as follows:
"B" tires have a rim width to the tire section ratio of 60% to 70% and a 15 deg. bead taper.
"H" tires are the same except they have a 5 deg. bead taper.
The letter "C" designates a cantilever type tire. It has a very narrow rim width, a section ratio less than 60% and a 15 deg. bead taper.
Aircraft Tire Characteristics
Aircraft tires today are offered in Bias Ply or Radial types, Tube-Type (TT) or Tubeless (TL). Bias Ply or Radial relates to the direction of the plies used in construction of the tire (either bias or radial). Traditional aircraft tires are bias ply tires. In these tires, the plies are wrapped to form the tire and give it strength. The angle of the plies in relation to the tire direction of rotation varies between 30° and 60°. Some modern aircraft use radial tires. The plies in radial tires are laid at a 90° angle to the direction of rotation of the tire. The Ply rating is used as an indicator of the relative strength of an aircraft tire. A tire with a high ply rating is a tire with high strength able to carry heavy loads regardless of the actual number of plies used in its construction. Tube-Type (TT) or Tubeless (TL) tires relate to the existence or not of a tube inserted inside the tire specifically designed to hold air.
Aircraft Tire Construction
Aircraft tires are constructed for the purpose they serve, therefore, the various tire components mentioned below may vary according to their design. Unlike automobile or truck tires, aircraft tires do not have to carry a load for a long period of continuous operation but must absorb the high impact loads of landing and be able to operate at high speeds even if only for a short time. The deflection built into an aircraft tire is more than twice that of an automobile tire. This enables it to handle the forces during landings without being damaged. Only tires designed for an aircraft as specified by the manufacturer should be used.
The various tire components and the functions contributed to the overall characteristics of a tire are briefly discussed below.
Rubber-coated layers of steel, fiberglass, rayon, and other materials located between the tread and plies, crisscrossing at angles, hold the plies in place. Belts provide resistance to punctures and help treads stay flat and in contact with the ground surface.
Tire Inner Liner
This is the innermost layer of a tubeless tire that prevents air from penetrating the tire.
A rubber-coated loop of high-strength steel cable that allows a tire to stay "seated" on a rim.
The tire bead is an important part of an aircraft tire. It anchors the tire carcass and provides a dimensioned, firm mounting surface for the tire on the wheel rim. Tire beads are strong and typically made from high-strength carbon steel wire bundles encased in rubber. One, two, or three bead bundles may be found on each side of the tire depending on its size and the load it is designed to handle. Radial tires have a single bead bundle on each side of the tire. The bead transfers the impact loads and deflection forces to the wheel rim. The bead toe is closest to the tire centerline and the bead heel fit against the flange of the wheel rim. An apex strip is additional rubber formed around the bead to give a contour for anchoring the ply turn-ups. Layers of fabric and rubber called flippers are placed around the beads to insulate the carcass from the beads and improve tire durability. Chafers are also used in this area. Chafer strips made of fabric or rubber are laid over the outer carcass plies after the plies are wrapped around the beads. The chafers protect the carcass from damage during mounting and demounting of the tire. They also help reduce the effects of wear and chafing between the wheel rim and the tire bead especially during dynamic operations.
Sipes are special treads within the tread of certain tires that improve traction on wet, dirty, sandy, or snowy ground surfaces.
The tread is the crown area of the tire and the one designed to come in contact with the ground. It is a rubber compound formulated to resist wear, abrasion, cutting, and cracking but also resist heat build-up. Most modern aircraft tire tread is formed with circumferential grooves that create tire ribs. The grooves provide cooling and help channel water from under the tire in wet conditions to increase adhesion to the ground surface. Tires designed for aircraft frequently operated from unpaved surfaces may have some type of cross-tread pattern. Older aircraft without brakes or brakes designed only to aid in taxi may not have any grooves in the tread. An all-weather tread may be found on some aircraft tires. This tread has typical circumferential ribs in the center of the tire with a diamond patterned cross tread at the edge of the tire. The tread is designed to stabilize the aircraft on the operating surface and wears with use. Many aircraft tires are designed with protective undertread layers. Extra tread reinforcement is sometimes accomplished with breakers. These are layers of nylon cord fabric under the tread that strengthen the tread while protecting the carcass plies. Tires with reinforced tread are often designed to be re-treaded and used again once the tread has worn beyond limits.
The spaces between two adjacent tread ribs are also called tread grooves. These allow water to escape effectively.
The outer edge of the tread that wraps into the sidewall area.
The sidewall is a layer of rubber designed to protect the carcass plies of an aircraft tire and also includes tire markings and information such as tire size and type. It may contain compounds designed to resist the negative effects of ozone on the tire. It also is the area where information about the tire is contained. The tire sidewall imparts little strength to the cord body. Its main function is protection. The inner sidewall of a tire is covered by the tire inner liner. A tube-type tire has a thin rubber liner adhered to the inner surface to prevent the tube from chafing on the carcass plies. Tubeless tires are lined with a thicker, less permeable rubber. This replaces the tube and contains the nitrogen or inflation air within the tire and keeps from seeping through the carcass plies. The inner liner does not contain 100 percent of the inflation gas. Small amounts of nitrogen or air seep through the liner into the carcass plies. This seepage is released through vent holes in the lower outer sidewall of the tires. These are typically marked with a green or white dot of paint and must be kept unobstructed. Gas trapped in the plies could expand with temperature changes and cause separation of the plies, thus weakening the tire leading to tire failure. Tube-type tires also have seepage holes in the sidewall to allow air trapped between the tube and the tire to escape.
Tire Body Plies
Carcass plies, also known as casing plies, are used to form the tire and provide its strength and resistance. Each ply consists of fabric, usually nylon, sandwiched between two layers of rubber to help bond with other plies and belts to seal in air. The plies are applied in layers to give the tire strength and form the carcass body of the tire. The ends of each ply are anchored by wrapping them around the bead on both sides of the tire to form the ply turn-ups. The angle of the fiber in the ply is manipulated to create a bias tire or radial tire as desired. Typically, radial tires require fewer plies than bias tires. Once the plies are in place, bias tires and radial tires each have their own type of protective layers on top of the plies but under the tread of the running surface of the tire. On bias tires, these single or multiple layers of nylon and rubbers are called tread reinforcing plies. On radial tires, an undertread and a protector ply perform the same function. These additional plies stabilize and strengthen the crown area of the tire. They reduce tread distortion under load and increase stability of the tire at high speeds. The reinforcing plies and protector plies also help resist puncture and cutting while protecting the carcass body of the tire.
Some tire sidewalls are mounded to form a chine. A chine is a special built-in deflector used on nose wheels of certain aircraft, usually those with fuselage mounted engines. The chine diverts runway water to the side and away from the intake of the engines. [Figure 7-E] Tires with a chine on both sidewalls are produced for aircraft with a single nose wheel.