Understanding the basics of aircraft tire construction and maintenance

Understanding the basics of aircraft tire construction and maintenance By Joe Escobar May/June 2001 Aircraft tires can easily be taken for granted. Their simplistic appearance may lead some to a false feeling of complacency. Many technicians...


Radial-ply tire construction

Radial Tire
Figure - 2
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A typical radial tire is illustrated in Figure 2. With their rigid belt, they provide increased landings and reduced rolling resistance. They have fewer components in their construction and are lighter than similarly sized bias ply tires. Components that differ from bias-ply construction as follows:
Overlay: A layer of reinforcing rubber coated fabric placed on top of the belts to aid in high speed operation.
Belt Plies: A composite structure that stiffens the tread area for increased landings. The belt plies increase the tire strength in the tread area.
Casing Plies: As in bias-ply tires, the casing plies are layers of rubber-coated fabric. However, unlike those in bias plies that run at opposite angles to one another, radial plies run radially from bead to bead.
Chippers: The chippers are layers of rubber-coated fabric applied at diagonal angles that improve the durability of the tire in the bead area.

Tire inspection
Tread CutsIn order to ensure safety and increase tire life, systematic inspections of mounted tires should be performed. A word of warning — Never probe cracks, cuts, or embedded foreign objects while the tire is inflated! Serious injuries could result. In addition, defects such as cuts, cracks, and bulges should be marked with a crayon or chalk prior to deflation since the defects may disappear when the tire is deflated. The following should be checked:
Tread wear: Treads should be visually inspected for wear. The tire should be replaced when tread has worn to the base of any groove at any spot or to a minimum depth specified in the aircraft maintenance manual. Tread wear can also be an indication of improper tire inflation. Refer to Figure 3 for tread wear indications.
Tread cuts: The tire should be inspected for cuts and other foreign damage. Follow the criteria from the applicable aircraft maintenance manual. If no specific criteria is outlined in the manual, the following can be used for guidance in determining tread cuts:

Typical Tread Wear Patterns
A-Normal
Even tread wear on this tire indicates that it has been properly maintained and run at correct inflation pressure.

B-Excessive
Worn to the breaker/casing plies, the tire should not be left in service or retreaded.

C-Overinflation
Continuous overinflation accelerates center tread wear. It reduces traction while making tread more susceptible to cutting.

D-Underinflation
Excessive tread shoulder wear results from chronic underinflation. It increases the chance of damaging shoulders and sidewalls which shortens tire life because of excessive flex heating.

• Any cut that extends into the casing plies on bias tires.
• Any cut into the belt on radial tires.
• Any cut that extends across one or more rubber tread ribs to the fabric.
• Rib undercutting at the base of any
cut or tread splice warrants replacement.
Sidewall damage: Tires should be replaced if weatherchecking, cracking, cuts, or snags extend down to the casing ply in the sidewall and bead areas.
Bulges: Bulges in any part of the tire tread, sidewall, or bead area are indicative of a separation or damaged tire. The area should be marked and the tire should be removed from service immediately.
Fabric fraying/groove cracking: Tires should be removed from service if groove cracking exposes any fabric or if cracking undercuts the tread ribs.
Flat spots: Flat spots can be caused by braking during touchdown or hydroplaning skids. Tires with flat spots don’t necessarily need to be removed from service unless fabric is exposed. However, if there is an objectionable unbalance issue, the tire assembly can be re-balanced or removed from service.
Radial tire sidewall indentation: Remove tire from service with 3mm or greater sidewall indentation.
Beads: The tire bead areas should be inspected next to the wheel flanges for heat-induced damage, especially if brake drag or severe braking was experienced.
Tire clearance: The tires should be inspected for marks that might indicate rubbing the wheel area due to inadequate clearance.
Wheel assemblies: The wheel assemblies should be inspected for damage. Wheels that are cracked or damaged should be taken out of service for repair or replacement.

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