Care and Service Manual

8/9/2019 Care and Service Manual

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Aircraft tire

C are & S ervice M anual


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Tableof contents

Introduction 6Aircraft TireConstruction 7The Tread 8The Undertread 8

Carcass Ply 8- For Bias - For Radial

The Beads 9Chafer Strips 9The Liner 9The Sidewall 9Products Uniqueto the Bias Tire 10

- The Tread Reinforcing Ply - Breaker Plies - ORION TM technology - Fabric Tread - Spiral Wrap

Products Uniqueto the Radial Tire 11

- The Protector Ply - Belt Plies

Chine Tires 11

is Not Recommended 22Store Tubes Properly 23Tire and Tube Age Limit 23Storage of Inflated Tireand Wheel Assemblies 23

Ozone 24Recommendations forStorage and Handling 25

General Mounting

InstructionsFor Aircraft Tires 26General 2Premounting Checklist 27

- Wheels - Tires

Mounting 29- Use of Inner Tubes

Bias Tires Radial Tires

- Lubrication of Tire Beads Bias Tires

Radial Tires - Tire/Wheel Assembly - Tire/Wheel Alignment

Branding 12

Tire serialnumber codes 17

General SafetyConsiderations 18Mounting 19Inflating 19Tires In Service 19

- Transportation

Storing AircraftTires And Tubes 20Handling Aircraft Tires 21 Avoid Moisture and ozone 21

- Ozone - What is it ? - Impact of ozone on tires

Designing for ozone 21Store away from fueland solvents 22Store in the Dark 22

Store Tires Vertically 22Horizontal Stacking of Tires


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- Inflating With Nitrogen - Special Procedure Properly Seat

Tube-Type Tires

Basic PressureRetention Check 31- Procedure

Emergency PressureRetention Check 32

- Procedure

Alternate PressureRetention Check 32

- Procedure

Sidewall Venting 33Not all aircraft tiresare vented 33

Storage of an Inflated Tireand Wheel Assembly 34

Mounting Tire/WheelAssemblyOn The Aircraft 36Visually InspectTire/Wheel Assembly 37Readjust Tire Pressure 37

Inflation PressureMaintenance 38Proper Inflation - Getting

the Most Out of Your Tires 39- Effects of Underinflation - Effects of Overinflation

Checking Duals for EqualOperating Pressure 40Proper Inflation - Settingthe Pressure Level 41

- Inflating and Reinflating the Tire/Wheel Assembly

- Loaded versus Unloaded Tires - Properly Inflating Tube - Type Tires

Effect of ambient temperatureon gauge pressure 42

- Effect of temperature - Proper Inflation - Standard for Maintaining Pressure Level

- Aircraft experiencing large ambient temperature differences between airports

Schedule and action 44- When to Check

Frequency Checking Hot Tires Compare tire pressures on the same given landing gear Single and Multiple tire gear Two Tire Gear Three or more tire gear

- Monitoring Inflation Pressure -

What To Do Pressure Loss 46

- Normal Response - Testing For Pressure Loss - Causes of Pressure Loss

Tire Growth Drop in Ambient Temperature Approved Calibrated Gauge Foreign Object Damage Improperly Seated Beads Valve Stem or Valve Core Valve Seal Wheel Half Parting Line O-Ring Seal Fuse Plug Pressure Release Plug Seepage Between Tire Bead and

Wheel Flange Leakage Through the Well Area Damaged Wheel Sealing Surfaces Damage to the Tire Innerliner Cracks or Splits in the Inner Tube

- Troubleshooting -Have You Considered?

Tire ServiceabilityCriteria 51On Aircraft Inspection With Tire Mounted 52

Removal Criteria - Wear

Water can affect traction 52- Typical Wear Conditions

Normal Wear

Overinflation Underinflation

Tableof contents


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For aircraft tires to delivermaximum performance, reliability,durability and safety, they must be

properly cared for and serviced.This manual is designed as a guideto the procedures to be used for allaspects of aircraft tire care andoperation. It provides detailedinformation about how to operateaircraft tires to achieve optimumservice. It also covers installation,removal and servicing techniques.It should be used in conjunctionwith the operating procedures givenby the aircraft and wheel

manufacturers.

The procedures given in thismanual apply to all Michelinmanufactured aircraft tires, new or

retreaded, regardless of the family name, current (Michelin Air,Michelin Air X, Michelin Aviator, Aviator, BF Goodrich, AAT,Silvertown) or future. The sameservice and care techniques shouldbe used for both Bias and Radialtires. In some specific cases, due tothe nature of bias and radial tireconstructions, differences in servicetechniques may exist. Whereapplicable, these differences havebeen noted.

Whether you operate a singleaircraft, or a fleet, the principles andprocedures contained in this manual will be of benefit.

If further information is needed,please contact your MichelinRepresentative.

See back cover for regional contacts.

Introduction


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Tireireconstructiononstruction

Aircraft tireconstruction


Tireconstruction


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A n aircraft tire must withstand a wide range of operational conditions.When on the ground, it must support the

weight of the aircraft.During taxi, it must provide a stable, cushioned ride while resisting heat generation,abrasion and wear. At take-off,the tire structure must be able to endure not only the aircraft load but also the forces generated at high angular velocities.Landing requires the tire to absorb mpact shocks while also transmitting

high dynamic braking loads to the ground. All of this must be accomplished while providing a long,dependable,reliable, service life.

These extreme demands require a tire which is highly engineered and precisely manufactured.For this reason,tires are designed as a composite of various rubber,fabric and steel products. Each of the components serves a very specific function in the performance of the tire.

To meet the aircraft demands of today and tomorrow, Michelin designs and produces two different and distinct tire constructions,the conventional

The undertread is a layer of specially formulated rubberdesigned to enhance the bonding

between the treadreinforcement/protector plies andthe carcass body. For those tiresdesigned to be retreaded, this rubberlayer will be of sufficient thickness toact as the interface for buffing the old tread assembly, as well as theliaison with the new retreadproducts.

A carcass ply consists of fabriccords sandwiched between twolayers of rubber. Today, the mostcommon fabric cord is nylon.The carcass body itself is made frommultiple layers of carcass plies, eachone adding to the strength and loadbearing capability of the tire.The carcass plies are anchored by wrapping them around bead wires,thus forming the PLY TURN-UPS .

FOR BIAS constructed tires,the carcass plies are laid at anglesbetween 30 and 60 to the centerlineor direction of rotation of the tire.Succeeding plies are laid with cord

cross-ply or BIAS tire and the RADIAL tire. Both nomenclatures describe the angular direction of the carcass plies.

While many of the components of bias and radial tires have the same terminology, the carcass ply angles are not the only difference between a bias constructed tire and a radial constructed tire.The technologies utilized are quite different involving different design parameters,compounds,and materials.

The tread refers to the crown areaof the tire in contact with the ground.Most Michelin tires are designed with circumferential grooves moldedinto the tread area. These provide amechanism to channel water frombetween the tire and runway surface which helps to improve groundadhesion.

The tread compound is formulatedto resist wear, abrasion, cutting,cracking and heat buildup.It prolongs the life of the casing by protecting the underlying carcass

plies.



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angles opposite to each other, toprovide balanced carcass strength.

FOR RADIALconstructed tires,each carcass ply is laid at an angle

approximately 90 to the centerlineor direction of rotation of the tire.Each successive layer is laid at asimilar angle. Radial constructedtires of the same size have a fewernumber of plies than do tires of abias construction, because the radialcord direction is aligned with theburst pressure radial force allowing for optimized construction.

The beads or bead wires anchorthe tire to the wheel. They arefabricated from steel wires layeredtogether and can be embedded withrubber to form a bundle. The bundleis then wrapped with rubber coatedfabric for reinforcement.

The liner in tubeless tires is a layerof rubber specially compounded toresist the permeation of nitrogen and

moisture through to the carcass. It isvulcanized to the inside of the tireand extends from bead to bead. Itreplaces the inner tube common totube-type tires. All Michelin manufactured Radialaircraft tires are certified for in-service operation to -55C.Beginning with manufactured date,June 1999, all Michelin Bias aircrafttires are certified for in-serviceoperation to -55C.In tube-type tires, a different, thinnerliner material is used to protect thecarcass plies from moisture and tubechafing, but is generally insufficientto maintain air retention.

The sidewall is a layer of rubbercovering the outside of the carcassplies. Its purpose is to protect thecord plies. In addition, the sidewallrubber contains anti-oxidants.They are slowly released over time toprotect the tire from ultraviolet andozone attack, which cause rubbercracking.

Depending on the size and designapplication, BIAS tires areconstructed with 2 to 6 bead bundles

(1 to 3 per side). By contrast, RADIALconstructed tires have 2 beadbundles (1 on each side) regardlessof tire size.

Chafer strips are strips of protec-tive fabric or rubber laid over theouter carcass plies in the bead areaof the tire. Their purpose is to pro-tect the carcass plies from damage when mounting or demounting andto reduce the effects of wear andchafing between the wheel and the

tire bead.


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Products uniqueto the bias tire

The tread reinforcing plyconsists of single or multiple layersof a special nylon fabric and rubberlaid midway beneath the treadgrooves and top carcass ply. Theseplies help to strengthen and stabilizethe crown area, by reducing treaddistortion under load, and toincrease high speed stability. They also offer a resistance to treadpuncture and cutting and help toprotect the carcass body.

Breaker plies (not shown) aresometimes used to reinforce thecarcass in the tread area of the tire.

ORION technology is adevelopment unique to MichelinBias construction. It consists of a

CROWN REINFORCEMENT placedon the inside of the tire. ThisCROWN REINFORCEMENTstrengthens and provides a moreuniform pressure distribution in thefootprint SLOWING THE RATE OF WEAR, improving landingsperformance in a lighter tire design.

Fabric tread (not shown) is aunique development for applicationon high speed military aircraft.

Multiple plies of nylon cord arelayered throughout the tread stock,reducing rubber distortion underload and high speeds, thus reducing heat normally generated by flexing.The laminates also control theformation of high speed standing waves. Improved resistance to cutsand punctures is also a benefit of this type of construction.

Spiral Wrap (not shown) is atechnique used with retreaded tires.

Individual textile cords are layed within the replacement tread rubberas it is applied to the tire casing.Cords are oriented to the top 1/2 -1/3 of the skid and are free to float.Because of their circumferentialorientation, the textile cords provideadded resistance to the cutting andtearing action associated withchevron cutting.

tread

tread reinforcing ply

undertread

carcass plies

sidewall

beads chafer strips

liner

carcass ply turn-ups

Bias Tire Construct


ORION technology


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Products uniqueto the radial tire

The protector ply is typically found in retreadable tiresand placed in the crown area justbelow the tread rubber. It providescut resistance protection to theunderlying belts and carcass plies.

Belt plies are laid between thetread area and top carcass ply.They restrain the outer diameter of the tire, providing a tread surfacewith greater resistance to squirmand wear as well as providing a moreuniform pressure distribution in thefootprint for improved landingsperformance.

tread

protector plyundertread

carcass pliesbelt plies

sidewall

bead linercarcass ply turn-ups

er strip

Radial Tire Construction

Single Chine Tire Dual Chine Tire

The chine tire is now in use as

standard equipment on many commercial jets. It is fully retreadable and may be usedon any aircraft provided adequateclearance is available.

Chine tires

The chine tire is a nose wheel tire

designed to deflect water and slushto the side and away from intakes onaft-fuselage mounted jet engines.

It consists of a flared upper sidewallprotrusion which deflects the spray pattern of water or slush displacedby the tires contact with the runway. A tire can have a single chine (onesidewall flared) for dual nose wheeltire configurations or double chines(both sidewalls flared) for singlenose wheel tire configurations.


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Brandingcommercial bias tire

typical Michelin branding layout

1. AEA: Association of European Airline

TRADEMARK

PART NO.

TUBELESS OR TUBE-TYPE DESIGNATION

QUALIFICATIONSTANDARD

LOAD RATING

MOLDED SKID

PLY RATING

SPEED RATING

EQUIPMENTIDENTIFICATION

AEA1 COD

COUNTRY OF ORIG

SIZE DESIGNATI

For details, see page 17

SERIAL NUMBER CODE


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Brandingcommercial radial tire


1. DGAC: Direction Gnrale de lAviation Civile / 2. FAA: Federal Aviation Administration / 3. All MICHELIN aircraft radials are tubeless

TRADEMARK

MOLDED SKID

FAA2 QUALIFICATIONSTANDARD

COUNTRYOF ORIGIN


DGAC1QUALIFICATIONSTANDARD

CONSTRUCTIONDESIGNATION

SIZEDESIGNATION

PART NO.

TUBELESS3 DESIGNATION

SPEED RATING

TYPE NUMBER

LOAD RATING

PLY RATING

CODEIDENTIFICATION


SERIAL NUMBER CODE


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Brandingmilitary bias tire


1.SCD: Specification Control Drawing / 2.MS: Military Specification / 3.OEM: Original Equipment Manufacturer / 4. USAF: U.S. Air Force

TRADEMARK


QTR NO.

CUT LIMITS

COUNTRYOF ORIGIN

SCD1 NO. OR MS 2 NO.OR OEM 3

SPECIFICATION NO.OR USAF4 NO.

TUBELESS ORTUBE TYPEDESIGNATION

PART N

SIZE DESIGNATIO

CODEIDENTIFICATION

NATIONAL OR NATOSTOCK NUMBER

For details, see page 17SERIAL NUMBER CODE

Application is program dependant

MAXIMUM WEAR LIMIT INDICATO

M

WL -

3


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Brandingmilitary radial tire


1. All MICHELIN aircraft radials are tubeless

TRADEMARK

INDEX LETTER

CODEIDENTIFICATION

COUNTRYOF ORIGIN

CONSTRUCTIONDESIGNATION

SIZEDESIGNATION

TUBELESS DESIGNATION1 PART NO.

FABRICATIONMONTH / YEAR

TYPE NUMBER


SERIAL NUMBER CODE

M W L - 3

Application is program dependant

MAXIMUM WEAR LIMIT INDICATOR


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Brandingbias retread tire

Branding

radial retread tire

RETREADER TRADEMA

TUBELEDESIGNATIO

AIRLINE CO

PLANT CODE

SIZE DESIGNATION

PLY RATING

SPEED RATING

MOLDED SKID

MOLDED SK

RATED SPEE

AEA TREAD CODE

MONTH &YEAR OFRETREAD

MONTH & YEAROF RETREAD

RETREADR-LEVEL

CASING SERINUMBE

PLANT CODE

AEA TREAD CODE

RETREAD R-LEVEL

RETRECONSTRUCTIO

DESIGNATIO

AIRLINE CODE

INTERNALMICHELIN CODE

MKC KANSAS CITY, USAMNW NORWOOD, USAMBO BOURGES, FranceMCN CUNEO, ItalieMNK NONG KHAE, Thailand


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Michelin tireserial number codes

Radial serial number definition:Last number of the manufacturing year (example: 9 for 1999).

3 numbers indicating themanufacturing day in Julian calendarexample: the tire was manufacturedhe 211th day of the year).

Code letter related to the facility andhe decade, see table below.

Unique production identificationnumber.

9 2 1 1 B 0 2 5

Bias Serial Number Definition:

Last number of the manufacturing year (example: 9 for 1999).

3 numbers indicating themanufacturing day in Julian calendarexample: the tire was manufacturedhe 211th day of the year).

Code letter related to the facility andhe decade, see table below.

Unique production identificationnumber.

9 2 1 1 P 0 0 0 2 5

Letter signification

The letter code in the tire serial number is used to identify both the manufacturing facility and the decade of manufacture.

t follows the rules below:

Manufacturing Through From Jan. 01, 1996 to from Jan. 01, 2000 to

Facility Dec. 31, 1995 Dec. 31, 1999 Dec. 31, 2009included included included

Bourges B B A

Clermont-Ferrand F F G

Greenville K K L

Nong Khae T T W

Norwood N P U


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q Keep pressure hose and fittingsused for inflation in good condi-tion.

q

Allow the tire to remain in theinflation cage for several minutesafter reaching full inflationpressure.

q Respect inflation pressures andall other safety instructions.

Tires in service

q Careful attention should beshown to tire/wheel assembliesbeing handled or in storage.

q Never approach a tire/wheel

assembly mounted on anaircraft that has an obviousdamage until that tire has cooledto ambient temperatures (allow at least 3 hours).

q Always approach a tire/wheelassembly from an oblique angle,in the direction of the tiresshoulder.

q Deflate tires before removing them from the aircraft unless thetire /wheel assembly is to beimmediately remounted on theaircraft, such as with brake

inspections. Deflate tires beforeattempting to dismount the tirefrom the wheel or before disas-

sembling any wheel component.Show caution when removing valve cores as they can be pro-pelled at a high speed from thevalve stem.

q The transportation of a service-able aircraft tire/wheel assembly should be in accordance withthe applicable regulatory body for the airline.Transportation of a serviceableinflated aircraft tire is covered by the U.S. Department of

Transportation Code of FederalRegulations, the International Air Transport Association (IATA),and other regulatory bodies.

q While serviceable tires may beshipped fully pressurized in thecargo area of an aircraft,Michelins preference is toreduce pressure to 25% of operating pressure or 3 bars /40 psi, whichever is the lesser.

q Remove from service tire/wheelassemblies found with one ormore tie bolt nuts missing.

A ircraft tire and wheel assemblies must operate under high pressures in order to carry the loads imposed on them.They

should be treated with the same respect that any other high pressure vessel would be given.Following the recommended procedures given throughout this manual,as well as those provided by authorities such as wheel manufacturers, air-framers and industry regulatory agencies,will minimize the risks and chance of injury.

Mounting

Follow the instructions given in the

section on General Mounting Instructions For Aircraft Tires.Be particularly attentive when:

q Rolling tires on the floor and using mechanical lifting equipment toavoid possible back injuries.

q Inspecting tires and wheels inadvance for possible shipping damage.

Inflating

q

When inflating tires, be sure touse a suitable inflation cage.

IMPORTANT: In the event of a conflict between

recommended procedures, be sure to contact your Michelin representative

before undertaking

the procedure in question.

Angle of Approach

Recommended Angle of Approach


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Storage

Storing aircraft tiresand tubes


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Typical ozone cracking

Ozone cracking in grooveTire can be lifted through center

through the center. Avoid the use of forks or other objects which havecorners that could damage the bead

surfaces. When possible, handle tiresby lifting or rolling.

Avoid moisture and ozone

Ozone - What is it ?

Ozone is a gas, a form of oxygen. Inthe earths atmosphere, where itoccurs naturally in small amounts,ozone plays a crucial geophysicalrole because of its intenseabsorption of solar ultraviolet

radiation. Additional ozone, created when industrial exhaust mixes withultraviolet rays, can be harmful.Ozone degrades organic matter, suchas rubber.

Impact of ozone on tires

Most of the natural and syntheticelastomers used in aircraft tires aresusceptible to ozone attack.Ozone in the air readily reacts withthe double bonds (unsaturation) in

the rubber molecules. The result of this reaction is the breaking of

molecular bonds and a degradationof the rubber, which lead to crack initiation. Continued stress, and

especially cyclic stress, causes thecrack to grow until it is visible as thecharacteristic surface crack,perpendicular to the direction of theapplied stress.

Designing for ozone

To aid in the control of ozone attack on rubber, the tire materials specialistadds waxes and protective chemicals.Some of these ingredients addressozone attack when the tire is in a

static state at room temperature;other ingredients are activated by heat and protect the tire once it is inservice. Further, the tire designer ismindful of the impact of shapes andcontours on stress concentrations.Still, steps need to be taken in storageto delay the effects of ozone attack. Wet or moist conditions have adeteriorating effect on tires andtubes, and can be even moredamaging when the moisturecontains foreign elements that are

further harmful to rubber and cordfabric.

T ires are designed to be tough,durable and to withstand large loads and high speeds.They can provide

years of reliable service if a few precautions are followed.The ideal location for tire and tube storage is a cool, dry and reasonably dark location, free from air currents and dirt.While low temperatures (not below 0C/32F)are not objectionable, room temperatures above 40C / 104 F are detrimental and should be avoided.

Handling aircraft tires

Care should be shown when hand-ling aircraft tires. While tough anddurable, tires can be damaged or cutby sharp objects or if excessive forceis used. Avoid lifting tires withconventional two prong forks of material handling trucks. Damageto bead mounting areas or theinnerliner can occur. A wide, flat,pincher type fork assembly of thetype that lifts the horizontal tire by squeezing against the tread surfaceis recommended. An alternate

recommended method would beto use a rounded bar to lift the tire


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Horizontal storage is not recommende

Strong air currents should beavoided, since they increase thesupply of oxygen and quite often

carry ozone, both of which causerapid aging of rubber.Particular care should be taken tostore tires and tubes away fromfluorescent lights, electric motors,battery chargers, electric welding equipment, electric generators andsimilar electrical devices, since they all create ozone.

Store away from fueland solvents

Make sure that tires do not comeinto contact with oil, gasoline, jetfuel, hydraulic fluids or otherhydrocarbon solvents, since all of these are natural enemies of rubberand cause it to disintegrate rapidly.Be especially careful not to stand orlay tires on floors that are coveredwith oil or grease. When working onengines or landing gears, tiresshould be covered so that oil doesnot drip on them.

If tires accidentally becomecontaminated, wash them off withdenatured alcohol and then with a

soap and water solution. Aftercleaning, be sure to remove any water that may have accumulatedin the interior of an unmounted tire.If after cleaning, the surfaceof the tire appears soft, or spongy,or bulges are present, the tire is notsuitable for service. Should you haveany doubt about the serviceability of such a tire, please contact yourMichelin Representative orauthorized repair station.

Store in the darkThe storage room should be dark,or at least free from direct sunlight. Windows should be darkened witha coat of blue paint or covered withblack plastic. Either of these willprovide some diffused lighting during the daytime. Black plasticis preferred since it will lower thetemperature in the room during the warm months and permit tires to bestored closer to the window.

Fluorescent or mercury vapor lightsshould not be used because they generate ozone. Low intensity

sodium vapor lights arerecommended. See the section onOzone for more information.

Stores tires vertically

Whenever possible, tires should bestored in regular tire racks whichhold them up vertically. The surfaceof the tire rack on which the weightof the tire rests should be flat and, if possible, 3 to 4 inches / 7.5 to 10 cm wide to prevent permanent

distortion of the tire.Horizontal stacking of tiresis not recommended

If tires are stacked horizontally, they may become distorted, resulting in mounting problems. This isparticularly true of tubeless tires.Those on the bottom of a stack may have the beads pressed so closely together that bead spreader tools will have to be used to properly space the beads for contact withthe wheel during initial inflation.

Store tires vertically in ra

Storing aircraft tiresand tubes

Protect tires from contaminants


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Tires which are stacked on topof each other, sidewall-to-sidewall,have increased stresses in the tread

grooves. If tires are stored foran extended period of time, or inan environment with high ozoneconcentration, ozone cracking is most likely to form in the treadgrooves.If tires must be stacked, they shouldnot be stacked for more than6 months maximum. The maximumstacking height:

q 3 tires high if tire diameter isgreater than 40 inches / 1 meter.

q

4 tires high if tire diameter is lessthan 40 inches inches / 1 meter.

Store tubes properly

Michelin tubes should always bestored in their original cartons, sothey are protected from light and aircurrents. If stored without theircartons, they should be wrapped inseveral layers of heavy paper.Tubes can also be stored by inflating slightly (not more than 0.06 bar / 1 psi)and inserting them in the same sizetire. This, of course, should only be

done as a temporary measure.Before mounting a tire and tubestored in such a manner, always

remove the tube from the tire andinspect the inside of the tire forforeign material, which, if notcleaned out, could cause irreparabledamage to both tube and tire.Under no circumstances shouldtubes ever be hung over nails orpegs, or over any other object whichmight form a crease in the tube.Such a crease will eventually produce a crack in the rubber andcause tube failure.

Tire or tube age limitMichelin aircraft tires or tubes haveno age limit and may be placed inservice, regardless of their age,provided all inspection criteria forservice/storage/mounting andindividual customer-imposedrestrictions are met.

Note: Certain regulatory agenciesrecommend further restrictingthe age of rubber products

used in the aircraft industry.The decision to adopt theserecommendations must bemade by the individual user.

Storage of inflated tireand wheel assemblies

Mounted tire/wheel assembly properly prepared and delivered toa line maintenance station as anairworthy replacement unit may bestored at full operational pressure

for up to 12 months, see commentsin the section on tire mounting found later in this manual.


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Ozone

Aircraft tiresand ozone


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Location:q Inside a warehouse away from direct sunlight or precipitation.

(Wet or moist conditions can carry other chemicals which can havea further damaging effect on tires.)

Storage Area Environment:q Temperatures should remain between 0C/32F and 40C/104F.q Use reasonably low intensity lighting (sodium vapor lamps are preferred).q Environment should be free of strong air currents and excessive dirt.

Ozone Sources:q Store away from fluorescent lighting, mercury vapor lamps, electric motors,

battery chargers, electric welding equipment, and electric generators.

Tire Storage:q Stand the tire such that it rests on its tread, whether on the floor or in a rack.q

This orientation should be used for any tire which will be held in storage formore than 1 months time. (Storage racks should provide an adequateamount of surface area to support the tire to prevent a distortion or setfrom occurring in the tread area).

q If high ozone concentrations can not be reduced or eliminated, each tireshould be protected by appropriate wrapping such as dark polyethyleneor paper.

Mounted Tire:q Mounted tires not immediately placed in service should be covered

or wrapped until they are to be installed on an aircraft.q To minimize the effects of ozone attack and where re-inflation capability

exists, tire pressure may be reduced to a value below operational pressure,

but not less than 25% of the operational pressure or 40 psi / 3 bars, whichever is less.

Recommendationsfor storage and handling

The following storage and handling conditions are strongly recommended to minimize the damaging effects of ozone:


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General mounting

General mounting instructionsfor aircraft tires


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Premounting checklist

Wheels

Careful attention to details is neces-sary to successfully mount aircraft tires for trouble-free service. Make sure you are thoroughly familiar with and inspect all key wheel parts before beginning to mount a tire.

To assist in this process, wheel manufacturers publish specific instructions in their maintenance and overhaul manuals. Follow their recommendations and procedures for wheel assembly and disassembly to obtain trouble-free mounting and dismounting.

Direct particular attention to the following:

q Ensure that the bead seatingarea of the wheel is clean anduncontaminated.

q Mating surfaces of the wheelhalves should be free of nicks,burrs, small dents, or otherdamage that could prevent thesurfaces from properly mating or sealing. Painted or coatedsurfaces should be in goodcondition; not badly chafed,chipped, etc.

q Be sure fuse plugs , inflationvalves and wheel plugs are ingood condition, properly sealedagainst loss of pressure andcorrectly torqued per themanufacturers instructions.

q 0-Ring grooves in the wheelhalves should be checkedfor damage or other debristhat would prevent the 0-Ring from properly seating.

General

Proper mounting procedures simplify

the job of servicing aircraft tires,while at the same time increasing safety and reducing the chances of damaging tires or wheels.Do not mount aircraft tires without the proper equipment, instructions,and operator training.

Be sure to know and understand all chemicals used on the tire and wheel.It is possible that under the high pressures and load exerted by the tire on the wheel,normally inert chemi-cals may contribute to rapid corro-sion and/or abrasion of the wheel,or deterioration of the rubber surface.

Virtually all modern aircraft wheels are of two types: split wheel type,i.e.,two halves joined by removable tie bolts, or the removable flange type.Both designs facilitate the mounting (and dismounting) of the tire.Show careful attention in handling,assem-bling and disassembling wheel com-

ponents to avoid damage to critical surfaces.

Wheel half and O-Ri


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q O-Rings themselves must beof the proper material , asspecified by the wheel manufac-

turer, for the intended applicationand temperature conditions.Inspect O-Rings for cracking,cuts, or other damage. Particularattention should be given topermanent deformations in theO-Ring. O-Rings found withdeformations should be replaced.Proper sealing of the wheelhalves is critical in providing trouble-free service.

q Should the inspection of a

used O-Ring for its integrity not be practical or manageable,replace with a new O-Ring witheach tire change.

Tires

Before mounting any tire, verify that

the tire is correct for the intendedapplication.Use the following checklist:

q Check that the tire markingsare correct for the requiredapplication (size, ply rating,speed rating, part number, TSOmarking).

q Visually inspect the outsideof the tire for : Damage caused by improper

shipping or handling of the tire. Cuts, tears or other foreignobjects penetrating the rubber.

Permanent deformations. Debris or cuts on the bead

seating surfaces. Clean the tirebead surfaces with either aclean shop towel, a soap/watersolution, or with denaturedalcohol as may be necessary.

Bead distortions. Cracking that reaches cords.

Contamination from foreignsubstances (oil, grease, brakefluid, etc.) which can cause

surface damage (blisters orswelling).

q Inspect the inside of the tireto be sure there is no foreignmaterial present. Be sure thatthe inner liner condition is good,that is, without wrinkles. Check for liner damage caused by improper shipping or handling of the tire.

Refer to the section on Tire

Serviceability Criteria for damages.If in question,tires should not be used and should be returned to a certified repair or retread station for further inspection and disposition.

WASHER

TIE BOLT

FIXTURE

INNER WHEELHALF ASSEMBLY

PACKING

OUTER WHEELHALF ASSEMBLY

Position Light Spot May Be Stamped

On Wheel

PACKING

NUT

WASHER

TIRE Aircraft Tire/Wheel Assem



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Mounting

Use of Inner Tubes

Bias TiresAll Michelin bias or cross ply tires,whether tube-type or tubeless, aresuitable for operation with tubesapproved for the particular tire sizeand application on tube-type wheels.

Radial TiresAll Michelin radial tires are of tubeless design. Never use an innertube or mount on a tube-type wheel.

Lubrication of Tire Beads

Bias TiresBecause of their typically wide beadflat, when installing bias tires onaluminum wheels, lubricate the toesof the beads with an approved 10%vegetable oil soap solution.

Do not use lubricant with magne-sium alloy wheels!

Lubricants manufactured from a petroleum base are not recommen-ded as hydrocarbons have a known

detrimental effect on rubber compounds.

Radial TiresFor radial tires, use of a mounting lubricant is not specified, unlessapproved by the airframer.

Tire/Wheel Assembly

Again, be sure that the wheel , tire,and assembly components are ingood condition and free of debris.

Lubricate the O-Ring (as specifiedby the wheel manufacturer) andinstall in the wheel groove orchannel. Be sure the O-Ring is free of kinks or twists.

Position the previously inspectedtire in front of the first wheel half.If a bias tire, lubricate the beads asrequired. Slide the tire on the wheel.

When mounting tube-type tires,dust the tube and the inside of thetire with tire talc or soapstone before

installing the tube. This will preventthe tube from sticking to the insideof the tire or to the tire beads.Dusting also helps the tube assumeits normal shape inside the tireduring inflation, and lessens thechances of wrinkling or thinning from irregular stretching. (Caution:Use care not to damage tube whenmounting.)

To be consistent with the practice of mounting the tire serial number to

the outboard wheel half, tubes should be installed in the tire with the valve projecting on the serial numbered side of the tire.

Assemble the two wheel halves,being sure to align the light point of each half 180 apart to insure theoptimum balance of the assembly.

When aligning the wheel halves, be careful not to damage the O-Ring in the wheel base which seals the wheel

halves.


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Tire/Wheel Alignment for Balance

The red balance mark on the lower

sidewall indicates the light point of the tires balance. Align this mark withthe heavy point of the wheel.In the absence of a balance mark,align the tires Serial Number withthe heavy point of the wheel (mainlanding gear position tires only).Many wheel manufacturers today identify either the light spot or heavy spot of the wheel with markings in theflange area. Follow their instructionson assembly and balance. Be sure toalign the tires light spot 180 from the

wheels light spot or directly in linewith the wheels heavy spot. In theabsence of specific wheel markings,align the tires red balance mark withthe wheel inflation valve.Some aircraft tubes feature balancemarks to indicate the heavy portion of the tube. These marks areapproximately 1/2 wide and 2 long.When inserting the tube in the tire, itsbalance mark should be aligned withthe balance mark on the tire. If thetube has no balance mark, alignthe valve with the balance mark on the tire.

A properly balanced tire/wheelassembly improves the tires overall wear characteristics. In addition to

severe vibration, an unbalancedassembly will cause irregular andlocalized tread wear patterns thatcan reduce the overall performancelife of the tire.

Be sure that nuts, washers, and boltsare installed in proper order and thatthe bearing surfaces of these partsare properly lubricated as required.Tighten to manufacturersrecommended torque values.

After the tire is mounted on the wheel , the assembly should beplaced in a safety cage for inflation with nitrogen. It is recommendedthat the cage be placed against anoutside wall that is strong enough to withstand the effects of an explosionof either the tire, tube or wheel.

The inflation pressure source should be located 10 meters / 30 feet away from the safety cage with a valve,regulator and pressure gauge installed at that point.The inflation line should then be run to the safety

cage and attached to the wheel valve.This arrangement allows the tire service person to inflate the tire

safely using the remote valve.Inflating With Nitrogen

Many regulatory agencies requireuse of nitrogen when inflating tiresfor aircraft above a specifiedMaximum Take-Off Weight (MTOW).Michelin recommends the use of adry, commercial grade nitrogen of atleast 97% purity when inflating allaircraft tires. Nitrogen provides astable, inert inflation gas while

eliminating the introduction of moisture into the tire cavity.

Aircraft operating procedures forinitial inflation and adjustments mustcomply with applicable instructions asgiven in FAR 25 or JAR 25.

Oxygen concentration should neverexceed 5%.


Tire balance mark

WARNING Aircraft tires can be operated up to or at

rated inflation pressure; extremely high inflation pressures may cause the aircraft wheel or tire to explode or burst, which

may result in serious or fatal bodily injury.

Aircraft tires must always be inflated with

a properly regulated inflation canister.

The high pressure side should never be used.

The safety practices for mounting and dismoun-

ting aircraft tires detai-led in this Manual must

be followed


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For safety: use a suitable metal inflation cage when inflating tires.

Store the inflated tire/wheelassembly for 3 hours.Check inflation pressure:Be sure that the ambienttemperature of the tire/wheelassembly has not changedby more than 3C/5F.Options: If inflation pressure is equal to

or greater than ( ) 90% of thespecified operating pressure,proceed to Step 4.

If inflation pressure is less than(


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After 12 hour storage period,check inflation pressure:Be sure that the ambient

temperature of the tire/wheelassembly has not changedby more than 3C/5F.

Options: If inflation pressure is equal to

or greater than ( ) 97.5% of thespecified operating pressure,accept the tire/wheel assem-bly for in-service usage or linemaintenance storage (seeStorage Section for recom-mendations on line mainte-nance storage).

Note: Re-inflate tire to thespecified operatingpressure.

If inflation pressure is less than(


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q Check for Leakage After the growth period, reinflatethe tire to the specified operating

pressure. Recheck the pressureafter a 24-hour period. A pressureloss of 5% or less is considerednormal. Be sure that the ambienttemperature of the tire has notchanged by more than 3C/5F. If a greater than 5% pressure lossoccurs, investigate the tire/wheelassembly for leaks. Do not put thetire into service until the leak source is identified and corrected.If the pressure loss is within theacceptable 5% limit, the assem-

bly is now ready to be installedon the aircraft.Note that once in service, thetire/wheel assembly maximumdaily (24 hours) pressure loss is5%. Typical rates are 0.2-2.0%per 24-hour period.

Sidewall venting

Aircraft tires have traditionally beendesigned to permit any air or nitrogentrapped in the cord body or thatdiffuses through the liner or tube to

escape through special sidewall vents.Tires requiring vent holes have themplaced in the lower sidewall. This

venting prevents pressure build-up within the carcass body which mightcause tread, sidewall, or ply separations. The location of each vent hole on the new tire isindicated by a colored paint dot.Simply apply a soap solution tothese vent markings. Theappearance of small bubbles willindicate diffusion. This bubbling isnormal and may be seen at any time while the tire is inflated. Maximumallowable diffusion is 5% for any

24-hour period. Pressure losses inexcess of 5% may indicate leakagefrom other sources. In that case, thetire and wheel assembly should becarefully tested for leaks, preferably by total immersion, before placing it into service. If no assembly leaksare found, dismount and have thetire inspected by the manufactureror a qualified repair shop.

Note: Do not identify a tire as aleaker solely on the rate ofbubbles from these vent

holes. A high rate of bubbleventing is not always anindicator of tire leakage.It is best to judge excessiveleakage of a tire/wheel assem-bly based on pressure loss asmeasured with acalibrated gauge, preferablythe same gauge used toinitially inflate the tire.

Not all aircraft tires are vented

Improvements in materials, tire designand fabrication make the need forlower sidewall venting unnecessary forall aircraft tires. This is particularly true for the physically smaller tiressuch as General Aviation and HighPerformance Military tires.

Knowing which tires have been vented is important. Tires requiring lower sidewall vents will have eithera green or white paint dot applied tothe area of each vent hole. Tires notneeding lower sidewall vents willhave no color dot in this zone.

Sidewall vent holes


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Storage of an inflated tireand wheel assembly

Once a tire has been properly mounted and the assembly verified for pressure retention,only minimal precautions need be taken.

q Do not expose the tire toexcessively high temperatures(greater than 40 / 104 F).

q Do not expose the tire todirect sunlight or to high ozoneconcentrations.

q Avoid contact withcontaminants (oil, grease, etc.).

q A Mounted tire/wheelassembly properly preparedand delivered to a line mainte-nance station as an airworthy replacement unit should meetthe following storage conditions:

The pressure level should beset at operational pressure forthe tire application. Do not

exceed operational pressure.

It is acceptable to STORE themounted assembly pressurizedin this range for up to

12 months. After 12 months,any inflated assembly whichhas not been introduced intoservice should be returned tothe wheel mounting shop.The following inspections andactions should be taken withthe assembly before returning it to service. This storage andre-inspection interval can berepeated multiple times solong as the tire meets allcriteria. However, to maximize

tire life, it is recommended torotate replacement stock.

Note: The conditions of storage, andthe tires response to thoseconditions, will determinewhether a stored, inflated tireis still airworthy. Time shouldnot be the measure by which atire is classified unserviceable.

Shop re-inspection should bemade with the assembly infla-ted to the operational pressure

level. The entire exterior of thetire should be visually inspec-ted for cracking (due to ozoneor ultraviolet attack), damages,or any other condition. If thelimits given in the chapter onTire Serviceability Criteriahave been exceeded, dismountthe tire from the wheel andreturn to the supplier.

Subject the assembly to thestandard air retention test to

verify that the assembly willstill meet the criteria of nomore than 5% pressure loss ina 24 hour period.

While in storage, if theassembly inflation pressure was being maintained using compressed air, deflate theassembly and re-inflate withnitrogen (per industry standards).



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Having met each of the aboveconditions, return thetire/wheel assembly to stock.

Note: The criteria for re-inspectionof the wheel must also bedetermined before returningthe assembly to service.

To minimize the effects of ozone attack and where re-inflation capability exists, tirepressure may be reduced to avalue below operational pres-sure, but not less than 25% of the operational pressure or

40 psi / 3 bars, whichever is less.q Transportation of

a serviceable aircrafttire/wheel assembly shouldbe in accordance with theapplicable regulatory body for the airline.

Transportation of a serviceableinflated aircraft tire is covered by theU.S. Department of Transportation

Code of Federal Regulations,the International Air Transport Association (IATA), and otherregulatory bodies.

While serviceable tires may beshipped fully pressurized in thecargo area of an aircraft, Michelinsrecommendation is to reducepressure to 25% of operating pressure or 3 bars / ~40 psi, whichever is the lesser. Reinflate tooperating pressure before mounting

on the aircraft.


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Mounting on aircraft

Mounting tire/wheelassembly on the aircraft


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Readjust Tire Pressure

Readjust Tire Pressure after

mounting the tire/wheel assembly on the aircraft. Operating pressuresare set by the airframemanufacturers based on a variety of factors including maximum ramp ortaxi weight, center of gravity anddynamic loading. Reference theOperators Manual for the particularaircraft.

Important:

Check pressure with aircraft load on tire.

Use loaded operating inflation pressure.

Operational pressure values are for loaded tires.

Loaded inflation pressure = 104% unloaded inflation pressure.

Visually Inspect Tire/WheelAssembly

Visually Inspect Tire/WheelAssembly for damage fromhandling, storage, orcontaminants. Look fordeformations, bulges, swelling,blisters, or other anomalies thatwould make the assembly unserviceable.

q Superficial cuts or cracks notreaching the cord body areacceptable for service.

q Groove cracking that doesnot reach the protector orreinforcing ply is acceptablefor service.

Follow the guidelines given in this Manual for serviceability.


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Inflation pressur emaintenance

Inflationpressure maintenance


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Be particularly alert to severetemperature drops, which will alsoreduce tire pressure. Repeated

pressure losses beyond the daily 5%,under constant temperatureconditions, may signal a slow leak inthe tire/wheel assembly.

To avoid false readings , tire pressureshould be checked on cool tires(air in a hot tire will expand, causing a temporary higher pressurereading). Wait at least 3 hours afterlanding or until the tire has reachedambient temperature as noted by carefully feeling with the palm of the

hand, before making pressurechecks.

If it is absolutely necessary to check pressures when tires are hot ,compare the relative pressuresbetween tires on the same landing gear positions (main or nose). Neverbleed pressure from a hot tire [SeeChecking Hot Tires later in thissection for details].

Effects of Underinflation

Too little pressure can be harmful to

your tires and dangerous to youraircraft and those in it.Underinflated tires can creep or slipon the wheel under stress or whenbrakes are applied. Valve stems canbe damaged or sheared off and thetire, tube, or complete wheelassembly can be damaged ordestroyed. Excessive shoulder wearmay also be seen.

Underinflation can allow thesidewalls of the tire to be crushed by

the wheels rim flanges underlanding impact, or upon striking theedge of the runway whilemaneuvering. Tires may flex over the wheel flange, with the possibility of damage to the bead and lowersidewall areas. The result can be abruise, break or rupture of the cordbody. In any case where the bead orcord body of the tire is damaged, thetire is no longer safe to use and mustbe replaced.

Proper inflation - gettingthe most out of your tires

The most important service you can perform on your aircrafts tires is to make sure they are properly inflated at all times.The more often you use the aircraft, the more often the tires need checking.I t is the Key to Optimum Service .

If you make one or more flights aday, tire pressure should be checkeddaily , with an accurate, calibratedgauge (preferably with a dial ordigital indicator appropriate for thepressure range of your tires).When installed, the TPIS (TirePressure Indicator System) can beused to make the daily inflationpressure check, provided the TPISindicators are verified against acalibrated pressure gauge at eachaircraft A check.

If you fly less than one time per day,you should check tire pressurebefore each flight.


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Severe underinflation may cause ply separation and carcass degradationbecause of the extreme heat,

the strain caused by the excessiveflexing action, or the occurrenceof premature standing waves(see photo). This same condition cancause inner tube chafing and aresultant blowout.

In dual tire applications,underinflation of one tire causes theother tire to carry a disproportionateamount of load. As a result, both tirescan be deflected considerably beyondtheir normal operating range,

potentially causing ply separationsand/or carcass degradation.

Effects of Overinflation

Tires operating under too muchinflation pressure are moresusceptible to bruising, cuts andshock damage. Ride quality as wellas traction will be reduced.Continuous high pressure operationwill result in poor tire wearcharacteristics (center wear) andreduced landings performance.

WARNING! Aircraft tires can be ope-rated up to or at rated inflation pressure. Extremely high inflation

pressures may cause the aircraft wheel or tire to explode or burst,which may result in serious or fatal bodily injury.Aircraft tires must always be inflated with a properly regulated inflation canister. The high pressure side should never be used.The safety practices for moun-ting and dismounting aircraft tires detailed in this Manual must be followed.

Checking Duals for EqualOperating Pressure

Tires mounted as duals or on thesame bogey, whether main or nose, whether bias or radial, should bemaintained at equal operating pressure. If pressures are not equal,the tire with the highest pressure willbe carrying an unequal proportionof the load even though there may be no perceptible differencebetween tire deflections.The graph on page 41 demonstratesthis concept.

If it is determined that dual-mounted tires are operating atunequal pressures (more than 5%is cause for special attention), inflateboth tires to their proper pressure.Make a logbook entry indicating theoriginal pressure differential, thedate and time corrected and theambient temperature. At eachsubsequent pressure check, thelogbook should be consulted.


Standing Wave in Laboratory conditions.


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If the same tire continues toevidence a pressure loss, it should bechecked for leakage (FOD, valve

core, etc.). If no obvious cause isfound, the tire should be removedand given a thorough inspectionuntil the reason for the pressure losscan be determined.

For mixability of bias and radialtires, see the section on Matching Dual Tires in this manual.

Proper Inflation - Setting thePressure Level

Inflating and Reinflatingthe Tire/Wheel Assembly

Whether for tubeless or tubetype,tire operating pressures should beset following the instructions givenby the airframe manufacturer. Fornewly mounted tires, follow theinstructions given in the section onGeneral Mounting Instructions ForAircraft Tires.

Loaded versus Unloaded Tires

Be sure that it is clear whether

operating inflation pressures aregiven for loaded or unloaded tireconditions. A tires inflation pressure when loaded will be 4% higher than when unloaded (Loaded pressure =1.04 x unloaded pressure).

Properly Inflating Tube-Type Tires

Air is usually trapped between thetire and the tube at the time of mounting. Although initial readingsindicate proper pressure, the

trapped air will seep out around thevalve stem hole in the wheel, andunder the beads. Within a few days,as the tube expands to fill the voidleft by the trapped air, the tire may become severely underinflated. Tocompensate for this effect, check tirepressure before each flight forseveral days after installation,adjusting as necessary, until the tiremaintains proper pressure.

60%

100%

100%

Pressure

Rated

100% pressure

100% load

100% pressure

100% load

200% Strut load

D e f l e c t i o n

Load BA120%80%

60% pressure

A load

100% pressure

B load

200% Strut load

Dual Tire Axle

Effects of Unequal Tire Pressure on Tire Loads

When required, reinflate tires totheir specified operating pressure with a dry, commercial grade

nitrogen of at least 97% purity.In some cases, nitrogen may not beavailable for adjusting tire inflation. When this occurs, clean dry air may be used as long as the oxygencontent does not exceed 5% of thetotal tire volume. If the 5% oxygenlimit is exceeded, the tire must bedeflated and then reinflated withnitrogen to the specified operating pressure.

WARNING! In the event of excessive heat build-up in the tire/wheel assembly (example, locked brakes),hydrocarbons released by the tire may spontaneously ignite in the presence of oxygen. A tire filled with air can explode,causing injury to persons and damage to equipment.


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Effect of ambient temperatureon gauge pressure

Effect of Temperature

Watch for severe changes in ambienttemperature. Changes intemperature affect gauge pressurereadings as follows:

1% change (increase) in inflation pressure reading for every 3C/5F change (increase) in temperature.

The above charts are a helpfulexample of the change in inflationpressure readings as a result of a

change in ambient temperature.For convenience, it is given in metricunits and in customary units.


Metric Units

50 12.9 14.1 16.4 17.6

40 12.5 13.7 15.9 17.1

Temperature Rise C 30 12.1 13.2 15.5 16.6

20 11.8 12.8 15.0 16.0

10 11.4 12.4 14.5 15.5

Specified Operating11 12 14 15

Pressure (bars)

10 10.6 11.6 13.5 14.5

20 10.2 11.2 13.0 14.0

Temperature Drop C 30 9.9 10.8 12.5 13.4

40 9.5 10.3 12.1 12.9

50 9.1 9.9 11.6 12.4

Units in C and B


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Proper Inflation Standard forMaintaining Pressure Level

A cold tire is defined as a tire whichhas come to equilibrium with itsoperating environment (ambienttemperature).

While the actual (ambient) temperatureof the cold tire will vary from locationto location and from season to season,the operational inflation pressure (P N),as specified by the airframemanufacturer for each aircraftconfiguration, is necessary to carry theload of the aircraft. This pressure value

is therefore needed regardless of theambient temperature . For example,if PN = 12 bars / 175 psi, this isthe pressure needed at any ambienttemperature.

Note: Do not reduce the pressureof the cold tire subjectedto frequent changesin ambient temperature.

[Refer to P. 44 for additional guidance.]

orq When pressure maintenance

is available at the destinationairport, check and readjust tooperating inflation pressure (Pprior to the next flight.

In all other cases, maintain theinflation pressure per the standardrecommendation.

Aircraft experiencing largeambient temperaturedifferences between airports

Large temperature differences placea special burden on aircraftoperations. As can be seen in thechart above, large changes inambient temperature will result incorresponding changes in gaugepressure. Aircraft flying long distances where a large (>30C/54F)decrease in ambient temperature will occur need to apply specificinflation maintenance procedures.One of two options should be

selected in this situation:q In the event that pressure main-

tenance is not available at thedestination airport, raise the ope-rating inflation pressure (P N) by 1% for each 5F / 3 C temperaturedrop relative to the departure air-port to insure adequate inflationpressure in the assembly atthe destination airport.

Note: Do not exceed maximum

rated loaded tire pressure.

Customary Units

100 192 216 240 264

80 186 209 232 255

Temperature Rise F 60 179 202 224 246

40 173 194 216 238

20 166 187 208 229

Specified Operating160 180 200 220

Pressure (bars)

20 154 173 192 211

40 147 166 184 202

Temperature Drop F 6O 141 158 176 194

80 134 151 168 185

100 128 144 160 176

Units in F and PSI


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Schedule and action

Measured Pressureas % of Operating Tire Condition Course of ActionPressure

More than 105 Overinflated q Because of variations in ambient temperature, gaugeaccuracy, etc., caution should always be shown beforeadjusting an overinflated pressure.

q It is recommended that the first overinflated reading berecorded in the aircraft log along with the ambienttemperature. After the 2nd confirmed reading >5%,readjust tire pressure to maximum of normal operating

range.

105 -100 Normal Operating q Do not adjust tire pressure.Pressure Range q Do not exceed tires maximum rated pressure value

(loaded), nor the wheels TSO qualification pressurevalue (loaded).

100 - 95 Acceptable Daily q Readjust tire pressure to maximum of normalPressure loss operating pressure range.


q Checking Hot Tires

Knowing if the pressure of a hot

tire is correct is nearly animpossible task. The air in a hottire expands, causing a temporary higher pressure reading. Theexact temperature is not knownand thus the relative pressure isalso unknown. As the tire cools,its pressure is also changing and will continue to do so untilambient temperature is reached.

A hot tire is one that has dynamically rolled under load on the aircraft and

has not been allowed to reachambient temperature (not beenallowed to cool for at least threehours). Tires at elevatedtemperatures will develop inflationpressures higher than the specifiedcold inflation pressure.

Because of unusual circumstances,it may be necessary to check the pressure of a tire when it is hot.

For example, check pressure if: tire shows excessive deflection

f light schedules make itimpossible to make a routinepressure check on a cool tire

tire is continually exposed todirect sunlight.

While no precise procedure can begiven for checking the pressure of a

hot tire, the following instructionsand precautions should be followed.

When to Check

q Frequency

Tires in service should have theircold inflation pressure checkeddaily to properly maintainoperating pressures. For aircraftoperating on a less frequent basis,inflation pressure should bechecked before each flight.

When installed, the TPIS (TirePressure Indicator System) can beused to make the daily inflationpressure check , provided the

TPIS indicators are verifiedagainst a calibrated pressuregauge at each aircraft A check.Understand that tires are capableof retaining pressure totolerances which will keep them well within 5% of the specifiedpressure each day. Since pressurelosses due to other causes canseriously affect performance andsafety, it still remains arecommended practice to verify the pressure value at least daily.

Continued on page 45


45/86

Schedule and action

Measured Pressureas % of Operating Tire Condition Course of ActionPressure

94 - 90 Accidental q Readjust tire pressure to maximum of normalPressure Loss operating pressure range.

q Record in log book.

q Recheck pressure after 24 hours.

q If after 24 hours, pressure loss is again greater thanthe daily acceptable pressure loss (>5%),remove tire/wheel assembly.

q Inspect tire/wheel assembly for causeof pressure loss.

89 - 80 Pressure Loss q Remove tire/wheel assembly from aircraft.

q Reinflate to specified operating pressure.

q If pressure loss is within daily acceptablepressure loss allowance (5%), inspect tire/wheel assemblyfor cause of pressure loss.

q If the cause cannot be found, dismount tire forinspection by an authorized repair station.

79 - 0 Major Pressure Loss q Remove the tire/wheel assembly.

q Remove the adjacent tire/wheel assembly.

q Replace tires*.

* If it is knownthat a major pressure loss occurred whilethe aircraft wasat rest or parkedand the wheelsdid not turn with weight onthem,the tire and the adjacent

tire can be saved. If doubtexists, tag the tire(s) and havean authorized retread repair station inspect them.

The basic rules to follow forcorrecting inflation pressure of hot tires on the same landing

gear:q Single and Multiple tire gear -

Should always be at least equalto, and may exceed, the specifiedoperating pressure.

q Two tire gear - If one tireis approximately equal intemperature but low in pressureit should be brought up to thepressure level of the other tire .In all cases, both tires should be

at least equal to or greater thanthe specified operating pressure.

q Three or more tire gear -Check all tires on the gear. Any tire that is approximately equal in temperature but low inpressure should have its inflationincreased such that all tires are within a 5% pressure range.In all cases, all tires should beat least equal to or greater thanthe specified operating pressure.

Note: If one tire has an abnormallyhigh pressure (>5%) ascompared to the other tires on

that gear, look for possiblecauses such as faulty brakes orincorrect pressure adjustmentat previous check.

Monitoring InflationPressure - What To Do

Checking and monitoring inflationpressure is usually performed onloaded tires. Be sure to know whether the operating inflationpressure is for loaded or unloaded

tire conditions.

q Loaded inflation pressure is 1.04 xUnloaded inflation pressure.

q Use an accurate, calibratedgauge, preferably with a dial typeindicator.

q Watch for changes in ambienttemperature. A 3C/5Ftemperature change will resultin a 1% tire pressure change.

q Compare tire pressures onthe same given landing gear

Pressures measured from tireson the same landing gearshould be of the same magni-tude. They should always beat least equal to the specifiedoperating pressure.

If any tire is less than 90% of minimum loaded service pres-sure, remove the tire from ser-vice.

In such cases, note reason for

removal and return the tire toan authorized repair facility for examination.

Aircraft flying between airports with a significant temperaturedrop, should be aware of theeffects of temperature oninflation pressure. See sectionEffects of Temperature.

Do Not Reduce The Pressure of a Hot Tire.

Continued from page 44


46/86


47/86

Testing For Pressure Loss

The source of a pressure loss can best

be determined by applying a soap solution to suspected areas of leakage or by total immersion of the tire and wheel assembly in a water bath.Begin with the most simple checks first:

q Check that the valve core is notleaking. Apply a small amountof soap solution on the end of the valve stem.If bubbles appear, replace thevalve core and recheck.Be sure that the valve stemthreads are not damaged.Otherwise, the valve core and thevalve cap will not fit properly.

Each valve should have a valvecap on it to prevent dirt, oil,moisture and other contaminantsfrom getting inside and damaging the core.

q Be sure that the valve is not bentor rubbing against the wheel. If damaged, dismount the tire andreplace the tube or valve.

q Check the fuse plugs or pressurerelief plugs with a soap and watersolution. If bubbles appear,

replace the valve core andrecheck.

q Inspect the tread and sidewallareas for FODs, cuts, snags, etc.Check suspected areas with asoap solution. If bubbles appear,the tire must be dismounted andrepaired by a qualified repairstation or scrapped.

q Totally immerse the tire/wheelassembly in a water bath. If a

water bath is not available, apply a soap or other leak detectorsolution to the entire tire/wheelassembly.The appearance of bubbles at any point other than at the vents inthe lower sidewall of the tire justabove the wheel flange willindicate a leak.

Note that nitrogen will diffuse through the sidewall vents for the entire life of an aircraft tire.

Look closely for bubbles in thetubewell area of the wheel to besure nitrogen is not leaking fromany fatigue cracks or at theO-Ring seal of the wheel halves.

q If no leak source other thanthe sidewall vents can be found,it will be necessary to dismountthe tire and make a furtherinspection.


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Causes of Pressure Losses

A tire that consistently loses inflation

pressure beyond the 5% daily allo-wance should be inspected to determi-ne the cause of the pressure loss.Some inspections can be made while the assembly remains mounted on the aircraft.Others will require the tire/wheel assembly to be dismounted from the aircraft and sent to the tire shop.Follow the guidelines given under the section Monitoring Inflation Pressure - What To Do.

There are a number of possible causesof pressure loss in a tire:

q Tire growth during the first12 hours after mounting andinflation to the specified operating pressure. This is entirely normal.

q To avoid a possible underinflationcondition, it is important that a tirenot be placed in service until it hasundergone the complete growthcycle and has been reinflated tothe specified operating pressure.

q An apparent pressure loss can becaused by a drop in ambienttemperature . Was the tire

inflated in a heated room andstored in an unheated one? Wasthe tire relocated from a warmclimate to a cold climate? For moredetails on the effects of ambienttemperature, see page 42.

q Use only an approvedcalibrated gauge , preferably of adial or digital type. It is best to usethe same gauge when monitoring a slow pressure loss in a tire/wheelassembly.

q Foreign object damage thatpenetrates the cord body and liner.Inspect the tire carefully for any FODs.

q Check for improperly seatedbeads . This condition can beidentified by comparing theposition of the tires lower sidewallannular rings, mold lines, orbranding. Look to see if they areuniform from side to side or thatthey are above the wheel flange.

This condition can be caused by: Insufficient inflation pressure. Bead toes (bias tires only) not

properly lubricated. Kinked or distorted beads. Accumulation of rubber on the

bead flats. Dirt trapped between the tire

and wheel.



49/86

q Leaks at the valve stemor valve core .- Put a small amount of water

on the end of the valve stemand watch for bubbles.If bubbles appear, replacethe core and repeat the check.

- Valve caps, finger tightened,should be used to prevent dirtfrom entering and holding openthe valve stem.

q Leaks at the valve seal(tubeless tires).- Valve holes in the wheel must

be free from scratches, gouges

and foreign material.- The proper O-Ring or grommet,as specified by the wheelmanufacturer, must be used.

q Wheel half parting line O-ringseal (tubeless tires) leaks inservice.

Twisting or failure to lubricatethe O-ring before installationmay cause leakage at the wheel mating surfaces.

Use of the wrong O-Ring com-pound, as specified by the

q Seepage between tire beadand wheel flange (tubelesstires) can occur. An inspection

should be made with particularattention to the following:

Look for exposure of cord bodyin the bead toe area or beadflat area. Exposed cords may act as a wick for nitrogen toescape along.

Foreign material trapped between the bead and wheel sea-ling surfaces causing a poorsealing between the tire and wheel.

Gouges or scratches resulting from handling or improper useof tire irons. Damage can alsooccur along the wheel half mating surfaces and leakagemay show in the O-ring sealarea.

Corrosion or wear in the beadledge area (usually toe area of the tire bead) will leak at thetire-wheel contact area.

wheel manufacturer, suitablefor the intended aircraft service(in particular low temperature

service) may also cause leakageat the wheel mating surfaces.

This type of leakage is very dif-ficult to diagnose since the in-service conditions causing theleakage are not reproducible ina shop.

q Leakage through the fuse plug(tubeless tires).

Use sealing gaskets specified

by the wheel manufacturer,suitable for the intendedaircraft service (in particularfor low temperature service).

A faulty fuse plug can allow aseepage of nitrogen and thus aloss of pressure.

q Pressure release plug (tubelesstires). Some wheel designs have apressure release plug. Thepotential causes of leakage arethe same as for a fuse plug.


50/86

A tube-type wheel convertedto tubeless application shouldhave the knurls removed.

Leakage will show at the tire- wheel contact area.

q Leakage through the wellarea of the wheel (tubeless tires)can occur from porosity or fatiguecracks, particularly if fatigue life isexceeded. Proper painting of the wheel should seal leakage fromminor porosity.

q Damaged Wheel SealingSurfaces or improperly

machined sealing surfaces may cause slow leakage. Correctirregularities before assembling the wheel. Foreign material orheavy paint can impair thesealing surface.

q Damage to the tire innerliner(tubeless tires).

q Small cracks or splits in theinner tube.

For a Mounted For a DismountedIn all cases, Tire/Wheel Assembly, For a Dismountebe sure Assembly, check tire Assembly,to account for: check for: and tube for: check wheel for

Initial Stretch Period(24 Hour Tire Growth)

X

Changes In Air Temperature X

Venting of Tubeless Tires X X

Release of Trapped Airin Tube-Type Tires X X

Cut or Puncture X X

Damaged Beads X

Improperly Seated Beads X

Leaking Valve core X

Other Valve Problems X X

Improper Installation of O-Rings X

Faulty Thermal Fuse or Installation X X

Porous Wheels X X

Improperly Torqued Wheel Tie Bolts X

Wheel Gouges and Scratches X X

Corrosion or Wear on Bead Ledge Area X

Knurls X

Damaged Sealing Surfaces X X

Wheel Assembly Holes X

Wheel Cracks X X


Troubleshooting -Have You Considered?

The above pressure loss troubleshoo-ting chart for tire/wheel assemblies will help you set up a uniform inspection procedure which can pre-vent problems and speed troubles-hooting. Determine the status of your assembly in the columns above.

Note: Tire inflation pressure must be

at operating or rated pressurewhen testing for points of pres-sure loss.

The point of leakage can bedetermined for the tire wheelassembly by applying a soapand water solution to the entireassembly or by immersing thetire/wheel assembly in water.


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Ser viceability criteria

Tire serviceabilitycriteria


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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 anemergency or particularlyrough landing, the tire, tubeand wheel should alwaysbe checked.

On-aircraft inspection withtire mounted

Removal Criteria - Wear

The tread area of the tire should bevisually inspected for any damageand the state of tread wear. Removalat the right time will optimize tirewear, while still protecting the lifeand investment of the carcass.In the absence of specificinstructions from the Airframer(Operations Manual, ServiceBulletins, etc.), a tire should

be removed from service for wearusing the following criteria :

Based on the fastest wearing location, remove tires:

q When the wear level reaches thebottom of any groove along morethan 1/8 of the circumference onany part of the tread,

or

q If either the protector ply (radial)or the reinforcing ply (bias) isexposed for more than 1/8 of the

circumference at a given location.Note: Tires reaching this wear point

on an aircraft at a remotestation can make a return-to-base flight(s) under standardoperating conditions withoutsacrificing retreadability of thecasing.

Note: In some military applications,the removal point of a tireis indicated by a red fabric

cord built into the tire ora wear depth plug.

Water can affect traction:

The accumulation of water on

runway surfaces can affect wettraction. Its affect is dependent ona number of factors including waterdepth, aircraft speed and runway surface conditions. The mosteffective method to minimizethe affects of water on traction isto reduce water depth or allow the water to escape from underthe footprint more rapidly. Many airport authorities today haveadopted cross-grooving for theirrunway surfaces which allowsfor rapid drainage of water.


Tread Reinforcing plies

Casing Outer Ply Belt Plies Casing Outer Ply Protector Ply

Wear Removal Criteria for Retreadable Bias Tire Wear Removal Criteria for Retreadable Radial


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Typical Wear Conditions:

q Normal wear

When tire wear has beenoptimized from propermaintenance and inflationpressures, the first point of wearout will be near thecenterline of the tire.Follow wear removal criteria.

q Overinflation When a tire has been operated with a higher pressure

than required for the aircraftloads, an accentuated centerline wear will be apparent.Overinflation has reduced thenumber of cycles to wearout andmade the tire more susceptibleto bruises, cutting and shock damage. Follow wear removalcriteria.

Belt Plies Casing Outer Ply Protector Ply Belt Plies Casing Outer Ply Protector Ply

Normal Wear Patterns - Radial Tire Effects of Overinflation - Radial


Casing Outer Ply


Casing Outer Ply

Normal Wear Patterns - Bias Tire Effects of Overinflation - Bias


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q Underinflation When a tire has consistently beenoperated underinflated, shoulder

wear will result. Severeunderinflation may cause ply separations and carcass heatbuild-up which can lead tothrown treads, sidewall fatigueand shorten tire life. Follow wearremoval criteria.


Belt Plies Casing Outer Ply Protector Ply

Effects of Underinflation - Radial Tire


Casing Outer Ply

Effects of Underinflation - Bias Tire


Cas

Belt PliesProtector Ply

q Worn Beyond RecommendedLimitsTire has been worn beyond

acceptable limits and into the topbelt plies (top carcass plies forbias - not shown). Tire is notretreadable.

q Flat SpottingThis tire wear condition is a resultof the tire skidding without

rotating, i.e., brake lockup orlarge steer angle.

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

If flat spotting does not extendto the protector ply or reinfor-cing ply, the tire can be left inservice.

If the localized loss of rubberresults in aircraft vibrations,even though no fabric hasbeen exposed, the tire must beremoved from service.


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q Asymmetrical WearThe tire has been operated underprolonged yaw and/or camber.

This camber angle can beinduced through landing gear orundercarriage deformation ormanufacturerssettings/tolerances. Taxiing withone engine or high speedcornering can also causeasymmetrical wear.In some cases, low inflationpressure will contribute to thiscondition. Tires that do notexpose any fabric can bedismounted, turned around and

remounted to even up wear. As long as standard wear criteriais met, the tire should remainin service.


Asymmetrical Wear - Radial T

Tire Flat Spot - Bias Tire

Worn Beyond Limits -Radial Tire


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q Serviceability Criteria/ LimitsFor Tire Damages When assessing tire damages, it is

best to make inspections with thetire inflated. Many damages thatare readily visible on an inflatedtire can no longer be seen whenthat tire is uninflated.

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

Tires removed should be tagged with a Reason For Removal.

A Systematic Approach to TireInspection assures that all partsof the tire are properly inspected. A recommended sequence of inspection is given above:

q Tread wear* Check for typical wear patterns.

Follow removal guidelines given

under the section RemovalCriteria - Wear.


2

4

3

1

Suggested approach : 1.Tread 2.Sidewalls 3.Bead areas 4.Innerliner


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q Tread Cuts/Foreign ObjectsTread cut removal limits are attimes given in specific

documentation such as aircraftmaintenance manuals, T.O.4T-1-3, technical documentation,airline operation manuals, tiresidewall markings, etc. Follow specific guidelines when given.

In the absence of specific cutremoval documentation , tiresshould be removed when:

Cuts , embedded objects orother injuries expose or pene-

trate the casing cord body (bias)or tread belt layers (radial).

If a cut or injury severs orextends across a tread rib, thetire should be removed fromservice.

Under cutting at the baseof any tread rib cut is causefor removal.Round foreign object openingsare acceptable up to

9.5 mm/0.375 in diameter.

Note: Tires removed for tread cutsor other injuries should besent to a certified repair

station to be repaired andretreaded or scrapped.

Tread Cuts Remove tire from service when : A. Depth of cut

exposes the casing outer ply (bias) or outer belt layer (radial).

B. A tread rib has been severed.

C. Undercutting occurs at the base of any cut.


B

AC

Radial Tire


Casing Outer Ply

B

AC

Bias Tire

Embedded objects take all form


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Chevron CuttingRemove from service if thechevron cutting results in

chunking which extends to andexposes the reinforcing orprotector ply more than 6 cm 2 /1.0 sq. in.

Tread Chipping/ChunkingRemove from service if thereinforcing ply (bias) or protector

ply (radial) is exposed for morethan 6 cm 2 / 1.0 sq. in.

Chevron Cutting: Remove tire from aircraft if:

Cutting causes the tread to loosen or chunk exposing the tread reinforcing ply or protector ply more than 6 cm 2 / 1 in 2

Continue in service if : Cutting

penetrates the

tread to a level less than one-half the molded skid depth even if the surface exhibits some shallow chipping or chunking.


Casing Outer Ply

Chevron Cutting - Bias Tire

Bel t P li es Cas ing Outer P ly Protector Ply

Tread Chipping / Chunking - Radial T

Chevron Cutting not exposingtextile can be left in service


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Peeled RibRemove from service if thereinforcing ply (bias) or protector

ply (radial) is exposed.Groove CrackingRemove from service if the groovecracking exposes the reinforcing ply or the protector ply for morethan 6 mm/1/4 in length.

Note: Authorization is givento return to maintenance base(


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Skid Burns from HydroplaningThis condition occurs on wet orice-covered runways. Remove

from service if the reinforcing ply or the protector ply is exposed.orif the severity of any flat spot issuch that aircraft vibration isunacceptable to operationalcrews.

Rubber reversion visible onthe surface does not affectthe performance capability of the underlying tread rubber andshould not be the determining

factor for removal.

Open Tread SpliceRemove from service if apparent.


Tread Splice - Radial Tire

Belt Plies

Abrasion & Reverted Rubber

Casing Outer Ply Protector Ply

Skid Burn - Radial Tire


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q Sidewall Cuts/Foreign ObjectsCuts, Snags, Gouges or OtherInjuries

Mark all damaged areas with alight colored crayon, wax markeror paint stick while the tire isinflated. Such injuries can bedifficult to find when the tire isuninflated.

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.

Chine tires:Any cut that severs or extends across the chine and is more than 1/2 the depth of the chine should be removed.

Sidewall Bulge/Blister/SeparationIf any are found, the tire should

be removed from serviceimmediately.

Sidewall Cut or Crack q If condition is within the

sidewall rubber, continue inservice.

q If sidewall cords are exposed ordamaged, remove the tire fromservice.

Bulge / Blister / Separation

Remove the tire from service.

Weather / Ozone CrackingRemove 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.


Sidewall Bulge

Tire Cut

Typical Ozone crack

Extends across chine

>1/2 depth of chine

Chine damage


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Serviceability Criteria /Operational Conditions:

q 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 obvioussigns of damage such as cuts,splits in the rubber, flat spotting,tread chunking, bulges, etc. Fordamages, follow the guidelinesgiven under Serviceability Criteria / Limits For Tire Damages .

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

It is recommended that an entry of the landing be made in theaircraft log as a future reference.Some tire damages, such asbottoming the tire, may notbecome apparent until severallandings later.

q Rejected Take off Aircraft experience various levelsof rejected takeoffs. Not all

rejected takeoffs are severeenough to warrant automatic tireremoval. The following guidelinesare recommended:

Where aircraft speed remainsbelow normal landing speedsand normal braking energiesare experienc

Documents

Care and Service Manual