Optimized tire performance is directly related to the use and care the tire is given. While the single most important action for obtaining optimum tire performance is a program of regular tire inflation maintenance, user (pilot) actions and the condition of the airport surfaces are also important. The following information is to help bring an awareness of these important factors which can further your tire investment.

TAXIING

Unnecessary tire damage and excessive wear can be prevented by proper handling of the aircraft during taxiing.

Most of the gross weight of any aircraft is borne by the main landing gear which may consist of two, four, eight, or more tires. The tires are designed and inflated to absorb the shock of landing and will normally deflect about three times more than a passenger car or truck tire. The greater deflection allows the tire to carry the heavy loads. It also causes more working of the tread, produces a scuffing action along the outer edges of the tread and results in more rapid wear.

If an aircraft tire strikes a chuckhole, stone, or some foreign object lying on the runway, taxi strip or ramp, there is more possibility of it being cut, snagged or bruised because of the high operational deflection. If one of the main landing gear wheels, when making a turn, drops off the edge of the paved surface, this may result in severe sidewall or shoulder damage. The same type of damage may also occur when the tire rolls back up over the edge of the pavement.

With dual main landing gear wheels, it is important that they equally share the weight carried by that landing gear assembly.

As airports grow in size, and taxi runs become longer, chances for tire damage and wear increase. Internal tire heat buildup also can be of concern. Speed, length of rolling and stops are all-important in influencing heat buildup. A taxi speed of 40 mph for 35,000 feet is demonstrated during the TSO certification of a tire. For either speeds or taxi distances greater than these limits, a 5-10 minute pause is recommended before takeoff.

For less foreign object damage in taxiing, all personnel should make sure that ramps, parking areas, taxi strips, runways and other paved surfaces are regularly cleaned and cleared of all objects that might cause tire damage.

PIVOTING BY USING BRAKES

Increased airport traffic and longer taxi runs are subjecting tires to more abrasion from turning and pivoting while braking.

Severe use of brakes under pivoting conditions can wear flat spots on tires and cause them to become out of balance, making premature retreading or replacement necessary. Pivoting on surfaces with heavy texture or a step condition can locally tear the tread from the casing. This tear may not show as a separation until later in the tire's service life.

Careful pivoting of an aircraft also helps prolong tire tread life. When an aircraft is turned by locking one wheel (or wheels), the tire is scrubbed, with great force, against the pavement. A small rock or debris that would ordinarily cause no damage can virtually be screwed into the tire. This scuffing and grinding action takes off tread rubber and places a very severe strain on the sidewalls and bead areas of the tire at the same time. Making wide radius turns will reduce tread rubber removal and sidewall stresses.

CONDITION OF AIRPORT FIELD

Regardless of preventive maintenance and the care taken by pilot and ground crew, tire damage is almost certain to result if runways, taxi strips, ramps and other paved field areas are in bad condition, strewn with debris or poorly maintained.

Chuckholes, pavement cracks or step-offs in the pavement can all cause tire damage. In cold climates, especially during winter, all pavement breaks should be repaired immediately.

Accumulated debris on paved areas, including hangar floors, is especially hazardous. Stones and other foreign material should be kept swept off all paved areas. Special attention should be paid to make sure that tools, bolts, screws, rivets and other repair materials are not left lying on an aircraft so that when it is moved, they fall to the floor. If a tire rolls over such material it can result in punctures, cuts or complete failure of the tire and tube.

AVOID CHEMICAL CONTAMINATION

Chemicals and hydrocarbons such as jet fuel, hydraulic fluids, grease, cleaning agents, etc., can damage aircraft tires by softening or deteriorating the rubber surface. During aircraft maintenance, tires should be covered to protect them from accidental spills. Keep runway surfaces clean so that tires are not parked in surface puddles. Immediately upon contact with a hydrocarbon substance, wash the contaminated area first with denatured alcohol then with a soap and water solution. If the rubber feels soft or spongy when probed, remove the tire from service.

NYLON FLAT SPOTTING

Nylon aircraft tires will develop flat spots under static load. The degree of this flat‑spotting will vary according to:

1. the temperature of the tire when the aircraft is first parked,
2. the pressure in the tire,
3. the load being applied to the tire while the aircraft is parked,
4. the ambient temperature,
5. the length of time the tire is subject to a combination of the above conditions,
6. the type of construction (under similar conditions, a radial tire will develop less flat spotting than will a bias tire).

On a practical level, aircraft maintenance personnel cannot influence all of these variables. To minimize the condition, inflation pressures should be kept at their specified operating levels and loads held to a minimum during the static load period.

Under normal conditions, a flat spot will disappear by the end of the taxi run. In the unusual case where deep flat‑spotting has occurred, additional taxiing is recommended prior to take‑off

An aircraft that is to remain idle for a period longer than three days should either be moved every 72 hours or blocked up so that no weight is on the tires. Aircraft in storage (out of service for more than 14 days) should be blocked up so that there is no weight on the tires.

CHEVRON CUTTING

Cross-cutting of runways is common at many major airports around the world. It improves drainage, reduces the danger of standing water and thus, decreases the risk of hydroplaning. However, the sharp‑edged ridges of concrete that result can cause chevron-type cutting of the tire tread ribs, particularly on the high-pressure tires used on jet aircraft.

Chevron cutting occurs during aircraft touchdown at "spin-up." As the tire begins to accept aircraft loads, it deforms slightly in these cross-grooves. At the same time rapid acceleration is occurring. The forces required to accelerate the tire to ground speed cause a tearing action which forms the chevron.

These cuts are at right angles to the ribs and rarely penetrate to the fabric tread reinforcement ply or protector ply, Refer to the section on "Tire Serviceability Criteria" for handling this condition.

HYDROPLANING

This condition results when, on a wet runway, the tire's tread is progressively lifted off the runway surface. A wave of water builds up in front of a rolling tire, allowing the tire to ride on the water and lose contact with the runway surface. Loss of traction, steering ability and braking action occurs. This action is usually referred to as "dynamic hydroplaning." Its occurrence is a function of water depth and aircraft speeds.

The same phenomenon can result when a thin film of water on the runway mixes with the contaminants present or if the surface texture of the runway is smooth. This is called, 'viscous hydroplaning." Generally the irregular condition of the runway surface is sufficient to break up this film.

Today, most airport runways are designed to minimize water buildup. Cross grooving is one example. In addition, tires have circumferential grooves which help to dissipate water.

An aircraft tire experiencing hydroplaning (usually viscous hydroplaning) may form an area of reverted rubber or skid burn in the tread. This area will be oval in shape similar to a flat spot. If the reinforcing ply or protector ply is not exposed, the tire can remain in service.

Note: A similar reverted rubber tread condition can occur if the tire slides on ice for any distance.

Tire removal criteria should be based on operational and tire condition factors. To be considered are: runway cross grooving, tire footprint area (number and remaining depth of grooves), and level of runway flooding. When operational and tire condition factors are conducive to hydroplaning, removal criteria should be advanced to 232" (1.5mm) remaining skid.

LANDINGS PER TREAD

Tire performance can be improved by using slow taxi speeds and by letting the aircraft roll during landing and by avoiding hard braking. Whenever possible, make large radius turns which minimize tire scrubbing.