A simple, easy-to-perform series of inspection procedures can prevent minor incidents from developing into major problems and help to optimize tire performance. Regular inspection is a small price to pay to protect your valuable tires, and the safety of your aircraft and the people it carries

Note: If an aircraft has made an emergency or particularly rough landing, the tire, tube and wheel should always be checked.

ON-AIRCRAFT INSPECTION WITH TIRE MOUNTED

Removal Criteria - Wear

The tread area of the tire should be visually inspected for any damage and the state of tread wear. Removal at the right time will optimize tire wear, while still protecting the life and investment of the carcass.

In the absence of specific instructions from the Airframer (Operations Manual, Service Bulletins, etc.), a tire should be removed from service for wear as set forth in the three following cases:

Case 1: Non-Retreadable Tires

1) At the first appearance of casing cords for bias tires and belt ply cords for radial tires.

• Based on the fastest wearing location.
• For any amount of exposed casing cord (bias) area.
• For any amount of exposed belt ply cord (radial) area.

Note: In some military applications, the removal point of a non-retreadable tire is indicated by a red fabric cord built into the tire or a wear depth plug.

Case 2 : Retreadable Tire

Retreadable tires should be removed before they are worn beyond retreadable limits.

Based on the fastest wearing location, remove tires:

1)       When the wear level reaches the bottom of any groove along more than 1/8 of the circumference on any part of the tread

or,

2)       If either the protector ply (radial) or the reinforcing ply (bias) is exposed for more than 1/8 of the circumference at a given location.

Note: Tires reaching this wear point on an aircraft at a remote station can make a return‑to‑base flight(s) under standard operating conditions without sacrificing retreadability of the casing.

Case 3 : When Hydroplaning is of Concern

When operational factors are conducive to hydroplaning, removal criteria should be advanced to 1.5mm (2/32") remaining skid.

Typical Wear Conditions

Normal wear

When tire wear has been optimized from proper maintenance and inflation pressures, the first point of wearout will be near the centerline of the tire. Follow wear removal criteria.

Overinflation

When a tire has been operated with a higher pressure than required for the aircraft loads, an accentuated centerline

wear will be apparent. Overinflation has reduced the number of cycles to wearout and made the tire more susceptible to bruises, cutting and shock damage. Follow wear removal criteria

Underinflation

When a tire has consistently been operated underinflated, shoulder wear will result. Severe underinflation may cause ply separations and carcass heat build‑up which can lead to thrown treads, sidewall fatigue and shorten tire life. Follow wear removal criteria.

Worn beyond Recommended Limits

Tire has been worn beyond acceptable limits and into the top belt plies (top carcass plies for bias ‑ not shown). Tire is not retreadable.

Flat Spotting

This tire wear condition is a result of the tire skidding without rotating, i.e., brake lockup or large steer angle.

1)       Tire should be removed from service if the flat spotting exposes the protector ply (radial tire) or reinforcing ply (bias tire).

2)       If flat spotting does not extend to the protector ply or reinforcing ply, the tire can be left in service.

3)       If the localized loss of rubber results in aircraft vibrations, even though no fabric has been exposed, the tire must be removed from service.

Asymmetrical Wear

The tire has been operated under prolonged yaw and/or camber. This camber angle can be induced through landing gear or undercarriage deformation or manufacturer's settings/ tolerances. Taxiing with one engine or high speed cornering can also cause asymmetrical wear.

In some cases, low inflation pressure will contribute to this condition. Tires that do not expose any fabric can be dismounted, turned around and remounted to even up wear. As long as standard wear criteria is met, the tire should remain in service.

Serviceability Criteria / Limits for Tire Damage

When assessing tire damages, it is best to make inspections with the tire inflated. Many damages that are readily visible on an inflated tire can no longer be seen when that tire is uninflated.

Be sure to mark all damages with a chalk stick before dismounting the tire.

Tires removed should be tagged with a "Reason For Removal."

A Systematic Approach to Tire Inspection assures that all parts of the tire are properly inspected. A recommended sequence of inspection is given as follows:

Tread Wear

Check for typical wear patterns. Follow removal guidelines given under the section "Removal Criteria - Wear."

Tread Cuts/Foreign Objects

Tread cut removal limits are at times given in specific documentation such as aircraft maintenance manuals, T.O.4T‑1‑3, technical documentation (FTU or TDS for radial tires), airline operation manuals, tire sidewall markings, etc. Follow specific guidelines when given.

In the absence of specific cut removal documentation, tires should be removed when:

1)      Cuts, embedded objects or other injuries expose or penetrate the casing cord body (bias) or tread belt layers (radial).

2)      If a cut or injury severs or extends across a tread rib, the tire should be removed from service.

3)      Under cutting at the base of any tread rib cut is cause for removal.

Round foreign object openings are acceptable up to 9.5 mm/0.375" in diameter.

Note : Tires removed for tread cuts or other injuries should be sent to a certified repair station to be repaired and retreaded or scrapped.

Mark all cuts, foreign objects, damages or leaks while tire is inflated. Use a light colored crayon, wax marker or paint stick. Damages can be difficult to find when a tire is uninflated.

Caution: Do not probe objects while tire is inflated.

Bulges or separations

Immediately remove the tire from service. Mark these areas with a color crayon before deflating.

Tread Chipping/Chunking

Remove from service if the reinforcing ply (bias) or protector ply (radial) is exposed for more than 6cm'/1.0 sq. in.

Chevron Cutting

Remove from service if it extends to and exposes the reinforcing ply or the protector ply

or  - if the chevron cutting results in chunking which extends to and exposes the reinforcing or protector ply more than 6cm2/1.0 sq.in.

Peeled Rib

Remove from service if the reinforcing ply (bias) or protector ply (radial) is exposed.

Groove Cracking

Remove from service if the groove cracking exposes the reinforcing ply or the protector ply for more than 6mm/l/4" in length.

Remove tire from service if tread reinforcing ply is exposed along the groove bottom more than 6mm/l/4" in length.

Rib Undercutting

Remove from service if undercutting extends more than 5.5mm/7/32" under the rib.

Remove tire from service if crack extends under the rib more than 5.5 m m/7/3 2 ".

Contamination From Hydrocarbons

Oil, grease, brake fluids, solvents, etc. can soften or deteriorate rubber components. immediately upon contact with a hydrocarbon substance, wash the contaminated area first with denatured alcohol, then with a soap and water solution. By pressing the rubber surface in the contaminated area versus the adjoining uncontaminated area, determine whether the rubber has become softened or "spongy". If so, remove the tire.

Skid Burns from Hydroplaning

This condition occurs on wet or ice‑covered runways. Remove from service if the reinforcing ply or the protector ply is exposed more than 160cml/25 sq. in.

or  - if the severity of any flat spot is such that aircraft vibration is unacceptable to operational crews.

Open Tread Splice

Remove from service if apparent.

Sidewall Cuts / Foreign Objects

Snags, Gouges or Other Injuries

Mark all damaged areas with a light colored crayon, wax marker or paint stick while the tire is inflated. Such injuries can be difficult to find when the tire is uninflated.

Caution: Do not probe cuts while tire is inflated.

• If sidewall cords are exposed or damaged, remove the tire from service.

• Cuts in the rubber which do not reach the cord plies are not detrimental to tire performance The tire can be left in service.

Sidewall Bulge / Blister / Separation

if any are found, the tire should be removed from service immediately.

Sidewall Cut or Crack

• If condition is within the sidewall rubber, continue in service.

• If sidewall cords are exposed or damaged, remove the tire from service.

Bulge / Blister / Separation - Remove the tire from service.

Weather/ Ozone Cracking

 Remove from service only if weather or ozone .  checking or cracking extends to the cords.

Important: Weather checking or cracks that do not reach the carcass cords are not detrimental to tire performance and do not constitute cause for removal. Tires showing only surface cracking can be left in service.

Serviceability Criteria / Operational Conditions

Hard Landing

After a particularly hard landing, tires, wheels, brakes and landing gear systems should be visually inspected for damage.

Inspect the tires for any obvious signs of damage such as cuts, splits in the rubber, flat spotting, tread chunking, bulges, etc. For damages, follow the guidelines given under Serviceability Criteria / Limits For Tire Damages.

If no damages are noted, the tire(s) should be left in service.

It is recommended that an entry of the landing be made in the aircraft log as a future reference. Some tire damages, such as bottoming the tire, may not become apparent until several landings later.

Rejected Takeoff

Aircraft experience various levels of rejected takeoffs. Not all rejected takeoffs are severe enough to warrant automatic tire removal. The following guidelines are recommended:

1) Where aircraft speed remains below normal landing speeds and normal braking energies are experienced, tires may be left in service. A minimum 30‑minute tire/ brake cooling period is required prior to the continuation of the aircraft's flight schedule.

2) Where aircraft speeds exceed normal landing speeds and high braking

energies are experienced, tires should be removed from service, labeled as an RTO tire and returned to the retreader for inspection and disposition.

Off AIRCRAFT INSPECTION WITH TIRE DISMOUNTED

A systematic approach to tire inspection

A Systematic Approach to Tire Inspection is recommended to insure that all areas are properly inspected.

The following system is recommended.

Inspect the Tread Area.

Follow the procedures given for On‑Aircraft Inspections

After the tread area Inspect Both Sidewall Areas.

Follow the procedures given for On‑Aircraft Inspections.

Inspect the Bead Areas.

• Check the entire bead area from just above the heel of the bead to the innerliner for chafing from the wheel flange or damage from tire tools.

• For Bias Tires

• An exposed chafer strip  on the bead face will normally cause no trouble and such a tire is fit for service and can be  retreaded.

• Damage, blisters or separations of the chafer strips are  repairable Send the tire to an authorized repair station.

• If carcass cords under chafer strip are damaged, the tire should be discarded.

•  For Radial Tires

• If bead area wear, along the wheel flange, exceeds lmm/l/32", remove the tire from service.

• If protruding bead wires, bead wire separations, or badly kinked beads are found,  the tire should be discarded.

Inspect the Tire's Innerliner.

• As with external areas, any tire with loose, frayed or broken cords inside should be discarded.

• Liner blisters, especially in tubeless tires, should be left undisturbed. do not pierce, puncture or cut them. To do so will destroy the air‑retaining ability of a tubeless tire.

• Generally confirm the good condition of the innerliner (e.g., no wrinkles).

Tube Inspection.

·         When inspecting tubes, do not inflate them with more pressure than is required to simply round out the inner circumference of the tube,  (never more than 1 psi).

·         Carefully inspect the inflated tube for leaks. First visually and then by submersion in water.

·         Examine the valve stem for leaks, signs of valve pad separation and bent or damaged valve stems.

·         Inspect the tube for severe wrinkles or creases. Remove from service if any are found. Wrinkles are evidence of improper fitting of the tube within the tire. Where wrinkles exist, chafing takes place, and that can result in loss of air or a blowout.

·         Inspect tubes for evidence of chafing by the toes of the tire beads. if chafing exists, remove the tube from service and scrap.

·         Examine for thinning. Where the heat is greatest, the tube has a tendency to be stretched over the rounded edge of the bead‑seat of the wheel. This is one of the reasons why, when mounting, tubes should always be inflated until the tire beads are in position, then completely deflated and reinflated to the final pressure. The stretch on the tube is then equalized throughout its inner and outer periphery.

·         Also check tubes for possible thinning out due to brake drum heat in the area where they contact the wheel and bead toes. The "set" or shape of the tube will help to determine when it should be removed from service because of thinning in the bead areas. Feeling the tube with the fingers will also reveal thinned areas.

·         On wheels with only one brake drum, this heat‑set condition will normally show up only on one side of the tube. in those cases where the brake drum is a considerable distance from the rim, it is unlikely that this condition will ever be experienced.

Inspect For Wheel Damage.

• Wheels should be inspected following the wheel manufacturer's recommendations.

• In general, make a visual inspection of the entire wheel. Wheels that are cracked or injured should be immediately taken out of service for further checking, repair or replacement.

• If used, check the condition of the thermal fuse plug or overinflation plug. Melted, pushed out or leaking plugs should be replaced. Be sure that sealing gaskets are the ones specified by the wheel manufacturer for the service conditions of the aircraft. Gaskets should be free from distortion and damage.

• If a fuse plug blows while the tire is rolling, the tire and its axlemate should be scrapped because both tire will have been subjected to overload conditions.