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1. Check daily when tires are cool
2. Inflate to worst conditions
3. Use dry nitrogen gas (safely)
4. Increase pressure 4% for tires under load
5. Allow 12 hour stretch after mounting
6. Never reduce the pressure of a hot tire
Remember, 1% pressure change for 5 degrees F (3 degrees C)
7. Equal pressure for duals
8. Calibrate inflation gauge regularly

Selection of the proper gauge is important. There are both digital and dial gauges available. The gauge should have a range that is close to and above pressures being measured. If a dial gauge is used, it should be easy to read and have increments of 5 psi.

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INFLATION PRESSURE
Note:
Keeping aircraft tires at their correct inflation pressure is the most important factor in any preventive maintenance program.

The problems caused by underinflation can be particularly severe. Underinflation produces uneven tread wear and shortens tire life because of excessive flex heating. Overinflation can cause uneven tread wear, reduce traction, make the tread more susceptible to cutting and increase stress on aircraft wheels. It is recommended that only dry nitrogen be used for tire inflation as nitrogen will not sustain combustion and will reduce degradation of the liner material and casing plies due to oxidation.

Tire pressures should be checked with an accurate gauge on a daily basis.

Ideally, pressures on high performance aircraft should be checked before each flight. Check only cool tires at least 2 to 3 hours after a flight. Use an accurate calibrated gauge. Inaccurate gauges are a major source of improper inflation pressures. Gauges should be checked periodically and recalibrated as necessary.

Goodyear recommends the use of a digital or dial gauge with memory needle in 5 psi increments. The inflation pressure recommended by the airframe manufacturer should be used for each tire. It must be determined if "loaded" or "unloaded" inflation pressure has been specified. When a tire is under load, the gas chamber volume is reduced due to tire deflection. Therefore, if unloaded pressure has been specified, that number should be increased by four percent (4%) to obtain the equivalent loaded inflation pressure.

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ADJUSTING FOR TEMPERATURE
When tires are going to be subjected to ground temperature changes in excess of 50 degrees F (27 degrees C) because of flight to a different climate, inflation pressures should be adjusted for the worst case prior to takeoff. The minimum required inflation must be maintained for the cooler climate; pressure can be readjusted in the warmer climate. Before returning to the cooler climate, adjust inflation pressure for the lower temperature. An ambient temperature change of 5 degrees F (3 degrees C) produces approximately one percent (1%) pressure change.

Excess Inflation Pressure Should Never Be Bled Off From Hot Tires - All adjustments to inflation pressure should be performed on tires cooled to ambient temperature.

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COLD PRESSURE SETTING
The following recommendations apply to cold inflation pressure setting:

1. Minimum service pressure for safe aircraft operation is the cold unloaded inflation pressure specified by the airframe manufacturer.
2. The loaded service inflation must be specified four percent (4%) higher than the unloaded inflation.
3. A tolerance of minus zero (-0) to plus five percent (+5%) of the minimum pressure is the recommended operating range.
4. If "in-service" pressure is checked and found to be less than the minimum pressure, the following table should be consulted. An "in-service" tire is defined as a tire installed on an operating aircraft.

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MOUNTED - TUBE-TYPE TIRES
A tube-type tire that has been freshly mounted and installed should be closely monitored during the first week of operation, ideally before every takeoff. Air trapped between the tire and the tube at the time of mounting will seep out under the beads, through sidewall vents or around the valve stem, resulting in an underinflated assembly.

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MOUNTED - TUBELESS TIRES
A slight amount of gas diffusion through the liner material and casing of tubeless tires is normal. The sidewalls are purposely vented in the lower sidewall area to bleed off trapped gases, preventing separation or blisters. A tire can lose as much as five percent (5%) of the initial inflation pressure in a 24-hour period and still be considered normal. If a soap solution is used to check leaks, it is normal for small amounts of bubbles to be observed coming from the vent holes.

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TIRE STRETCH
The initial stretch or growth of a tire results in a pressure drop after mounting. Consequently, tires should not be placed in service until they have been inflated a minimum of 12 hours, pressures rechecked, and tires re-inflated if necessary.

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CASING FLAT SPOTTING
Loaded tires that are left stationary for any length of time can develop temporary flat spots. The degree of this flat-spotting depends upon the load, tire deflection and temperature. Flat-spotting is more severe and more difficult to work out during cold weather. Occasionally moving a stationary aircraft can lessen this condition. If possible, an aircraft parked for long periods (30 days or more) should be jacked up to remove weight from the tires. Under normal conditions, a flat spot will disappear by the end of the taxi run.

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COLD WEATHER PRECAUTIONARY HINTS
When extreme drops in temperature are experienced, these precautionary tips can help provide safe, trouble-free operation:

1. Follow Goodyear's recommendations on mounting as described on new tire label.
2. Use only new wheel manufacturer approved O-ring seals with the proper cold weather properties, properly lubricated and installed.
3. Use only an accurate calibrated pressure gauge.
4. Be sure that wheel bolts are properly torqued per wheel manufacturer's instructions.
5. Aircraft parked and exposed to cold soak for a period of time (1 hour or more), should have tire pressure checked and adjusted accordingly.
6. High speed taxis and sharp turns should be avoided to prevent excessive sideloading.
7. An important fact to remember is that every 5 degrees F (3 degrees C) change in temperature will result in a corresponding 1% change in tire pressure.
8. Do not reduce the inflation pressure of a cold tire that is subjected to frequent changes of ambient temperature.

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SPECIAL PROCEDURES - ABOVE NORMAL BRAKING ENERGY USE
Tires subjected to above normal braking energies (such as an RTO) should be removed and scrapped. Even though visual inspection may show no apparent damage, tires may have sustained internal structural damage that could result in premature failure. Also, all wheels should be checked in accordance with the applicable Wheel Overhaul or Maintenance Manual.

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Data for new tire diameters after a 12 hour stretch period, at rated inflation pressure, are available in Goodyear's Aircraft Tire Data book. The maximum grown diameter is calculated using Tire and Rim or ETRTO formulas and these formulas are also found in Goodyear's Aircraft Tire Data book. If help is needed with these calculations, please contact your local Goodyear representative.

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PROTECTING TIRES FROM CHEMICALS AND EXPOSURE
Tires should be kept clean and free of contaminants such as oil, hydraulic fluids, grease, tar, and degreasing agents which have a deteriorating effect on rubber. Contaminants should be wiped off with denatured alcohol, then the tire should be washed immediately with soap and water. When aircraft are serviced, tires should be covered with a waterproof barrier.

Aircraft tires, like other rubber products, are affected to some degree by sunlight and extremes of weather. While weather-checking does not impair performance, it can be reduced by protective covers. These covers (ideally with light color or aluminized surface to reflect sunlight) should be placed over tires when an aircraft is tied down outside.

Store tires away from fluorescent lights, electric motors, battery chargers, electric welding equipment and electric generators, since they create ozone which can cause rapid aging of rubber.

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CONDITION OF AIRPORT SURFACES
Regardless of the excellence of any preventive maintenance program, or the care taken by the pilot and ground crew in handling the aircraft, tire damage will certainly result if runways, taxi strips, ramps and other paved areas of an airfield are in a poor condition or improperly maintained.

Chuck holes, cracks in pavement or asphalt or stepoffs from pavement to ground can cause tire damage. Pavement breaks and debris should be reported to airport personnel for immediate repair or removal.

Another hazardous condition is the accumulation of loose material on paved areas and hangar floors. These areas should be kept clean of stones, tools, bolts, rivets and other foreign materials at all times. With care and caution in the hangars and around the airport, tire damage can be minimized.

Many major airports throughout the world have modified their runway surfaces by cutting cross grooves in the touchdown and rollout areas to improve water runoff. Cross grooves vary in size and shape. This type of runway surface can cause a pattern of chevron-shaped cuts in the center of the tread. As long as this condition does not cause chunking or cuts into the fabric, the tire is suitable for continued service. See picture of a typical example of chevron cutting in the tread photo section.