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Care & Service Manual

1. Te S S d T ZS 5 lp MICHELIN AIRCRAFT TIRE Care 8 Service Note This document Michelin Reference MAT CSM 01 Rev A supercedes Reference MAT CSM 95 Rev MAT CSM 95 Rev Michelin document MAINT 0013 and the document entitled Michelin Aircraft Tire Care amp Maintenance contents 6 Introduction Aircraft Tire Construction For Bias For Radial The Tread Reinforcing Ply Breaker Plies ORION technology Fabric Tread Spiral Wrap The Protector Ply Belt Plies 7 Branding Tire serial number codes General Safety Considerations Transportation Storing Aircraft Tires And Tubes void Moisture and Ozone What is it Impact of ozone on tires 12 17 18 20 Ozone 24 General Mounting Instructions For Aircraft Tires 26 ral mount Wheels Tires Use of Inner Tubes Bias Tires Radial Tires Lubrication of Tire Beads Bias Tires Radial Tires Tire Wheel Assembly Tire Wheel Alignment contents Inflating With Nitrogen Special Procedure Properly Seat the Most Out of Your Tires 39 Effects of Underinflation Tube Type Tires Effects of Overinflation Basic Pressure Checking Duals for Egual Retention Check 31 Operating Pressure 40 Liuda Proper Inflation Setting Emergency Pressure the Pressure Level 41 Retention Check 32 Inflating and Reinflat
2. MICHELIN AIRCRAFT TIRE gt liner in tubeless tires is a layer of cubes compounded to resist the permeation of nitrogen and moisture through to the carcass It is vulcanized to the inside of the tire and extends from bead to bead It replaces the inner tube common to tube type tires All Michelin manufactured Radial aircraft tires are certified for in service operation to 55 Beginning with manufactured date June 1999 all Michelin Bias aircraft tires are certified for in service operation to 55 C In tube type tires a different thinner liner material is used to protect the carcass plies from moisture and tube chafing but is generally insufficient to maintain air retention The sidewall is a layer of rubber covering the outside of the carcass plies Its purpose is to protect the cord plies In addition the sidewall rubber contains anti oxidants They are slowly released over time to protect the tire from ultraviolet and ozone attack which cause rubber cracking The tread reinforcing consists of single or multiple layers of a special nylon fabric and rubber laid midway beneath the tread grooves and top carcass ply These plies help to strengthen and stabilize the crown area by reducing tread distortion under load and to increase high speed stability They also offer a resistance to tread puncture and cutting and help to protect the carcass body Breaker plies not shown are sometimes u
3. SLR1 SLR2 OD1 0 2 loaded radius information Radial tires approved for application on the same axle bogie of an aircraft will operate at the same inflation pressure El Bias tires on one main lan ding gear bogie and Radial tires on the other Any proposed mixing must be approved by the airframer Radial and Bias tires approved for the same application may be of different overall diameters when stood side by side It is important that the static loaded radius of the two tires be the same Radial tires approved for application on the same aircraft but different axles or bogies may operate at different inflation pressu res than the Bias tire This is mostly true of high performance military applications When operating tires in combination it is important to respect load and inflation recommendations There is a limit to the load any aircraft tire can safely carry The maximum static load limits as recommended by the Tire and Rim Association and or the European Tyre and Rim Technical Organization are shown in the Load and Inflation Tables in the document entitled Michelin Aircraft Tire Engineering Data Similar information is also contained in the T amp RA Yearbook and ETRTO Data Book Overloading a tire puts undue strain on the cord body and beads of the tire reducing its safety factor and service life It further increases the chance of bruising impact and flex breaks in t
4. e Radial tires e Same Size e Same Type e Within the same Static Loaded Radius limits For Civil application Radial tires use grown dimensions REFERENCES Tire and Rim Association inflated dimensions Michelin Aircraft Tire Engineering Databook s For military application Radial tires use inflated dimensions REFERENCE Michelin Aircraft Tire Engineering Databook New versus Retreaded tires The practice of mounting both new and retreaded tires on the same axle is acceptable Follow the same guidelines as above MICHELIN AIRCRAFT TIRE Mixability The mixability of aircraft tires has become an important issue in recent years It is Michelin s position that the ultimate authority for approving mixability of different tires on an aircraft lies with the aircraft manufacturer or aircraft design authority who alone has full knowledge of all aircraft performance requirements A key point for mixability is that matched tires carry the same load at the same pressure Three possible configurations of tires exist The following guidelines are given for mixability e Bias Bias e Bias tires can be mixed on the same axle or bogie if the follo wing requirements are met The tires are of the same size designation All tires are qualified for the aircraft application All tires meet the type designation and overall Matching and mixability of
5. D Re inflate the tire to the specified operating pressure After a 24 hour storage period check inflation pressure Be sure that the ambient temperature of the tire wheel assembly has not changed by more than 3 5 Options e If inflation pressure is equal to or greater than 2 9596 of the specified operating pressure accept the tire wheel assembly for in service usage or line main tenance storage see Storage Section for recommendations on line maintenance storage Note Re inflate tire to the specified operating pressure f inflation pressure is less than 95 of operating pressure reject the tire wheel assembly applied Note this procedure recommends a tire inflation check be performed before each flight during the first 48 hours after the assembly has been put into service Alternate pressure retention check This alternate historical procedure is designed to provide a more complete check of tire wheel assembly pressu re retention prior to releasing them for use on aircraft The procedure is particularly beneficial when in service pressure retention issues have been encountered Procedure e Allow for Tire Growth Newly mounted tire wheel assem blies should stand for 12 hours to allow for normal tire growth cord body stretching and to verify that the assembly is without leaks After 12 hours inspect the assem bly carefully Check the tire pres sure drop A 1096 drop du
6. PART NO SIZE DESIGNATION 1 SCD Specification Control Drawing 2 MS Military Specification Original Equipment Manufacturer 4 USAF U S Air Force A EE 1 r m 2 S up ty TRADEMARK INDEX LETTER CODE IDENTIFICATION SERIAL NUMBER CODE FABRICATION MONTH YEAR 23318053 TYPE NUMBER 9915055 1177 ANCE N pr A 2 gt 7 5 0 COUNTRY OF ORIGIN sk CES 7 gt Ww CONSTRUCTION GL SIZE TUBELESS DESIGNATION D PART NO 1 All MICHELIN aircraft radials are tubeless AEA TREAD CODE MOLDED SKID SPEED RATING PLY RATING SIZE DESIGNATION PLANT CODE AEA TREAD CODE MONTH amp YEAR OF RETREAD RETREAD R LEVEL AIRLINE CODE INTERNAL MICHELIN CODE MICHELIN RETREAD R LEVEL MONTH 8 YEAR OF RETREAD 49 RETREADER TRADEMARK af T 1 4 TUBELESS DESIGNATION 301 gs secs gonatt RETREAD CONSTRUCTION DESIGNATION AIRLINE CODE CASING SERIAL NUMBER RATED SPEED MOLDED SKID 9195 HENE KANSAS CITY USA NORWOOD USA BOURGES France CUNEO Italie NONG KHAE Thailand Michelin tire serial number codes MICHELIN AIRCRAFT TIRE Radial serial number definition 92 11 B 0 2 5 DA Mur Last number of the manufactur
7. Aircraft Tire Wheel Assembly Contamination from foreign substances oil grease brake fluid etc which can cause surface damage blisters or swelling e Inspect the inside of the tire to be sure there is no foreign material present Be sure that the 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 Use Inner Tubes Bias Tires All Michelin bias or cross ply tires whether tube type or tubeless are suitable for operation with tubes approved for the particular tire size and application on tube type wheels Radial Tires All Michelin radial tires are of tubeless design Never use an inner tube or mount on a tube type wheel Lubrication of Tire Beads Bias Tires Because of their typically wide bead flat when installing bias tires on aluminum wheels lubricate the toes of the beads with an approved 10 vegetable oil soap solution Radial Tires For radial tires use of a mounting lubricant is not specified unless approved by the airframer Tire Wheel Assembly Again be sure that the wheel tire and assembly components are in good condition and free of debris Lubricate the O Ring
8. Tread Splice Radial Tire Skid Burns from Hydroplaning Open Tread Splice This condition occurs on wet or Remove from service if apparent ice covered runways Remove from service if the reinforcing ply or the protector ply is exposed Or if the severity of any flat spot is such that aircraft vibration is unacceptable to operational crews Rubber reversion visible on the surface does not affect the performance capability of the underlying tread rubber and should not be the determining factor for removal Sidewall Cuts Foreign Objects Cuts Snags Gouges or Other Injuries Mark all damaged areas with a light colored crayon wax marker or paint stick while the tire is inflated Such injuries can be difficult to find when the tire is uninflated Caution Do not probe cuts while tire is inflated If sidewall cords are exposed or damaged remove the tire from service e Cuts in the rubber which do not reach the cord plies are not detrimental to tire performance The tire can be left in service e 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 Tire serviceability Extends across chine gt 1 2 depth of chine criteria Chine damage Sidewall Bulge Blister Separation If any are found the tire should be removed from service immediately Sidewall Cut or Crack e If condition is within the sidewall rub
9. Vibration shimmy and other similar conditions are usually blamed on improper tire balance Imbalance is a well known and easily understood cause for vibration In many cases though this may not be the cause There are a number of specific aspects of the tire wheel and gear assembly which can be the cause or contribute to aircraft vibration As with any concern systematic approach should be taken to isolating its cause e Check that the tire has been inflated to the proper inflation pressure e Follow airframer s recommendation e Be sure an accurate calibrated pressure gauge has been used e Check that dual tire inflation is equalized between tires and per the operating specification e Assure that the tire reached full growth before it was installed on the aircraft e Allow at least 12 hours at operating or rated pressure for the tire to attain full growth e Check that the beads of the tire have been properly seated Check the tire for flat spotting or uneven wear If flat spotting does not extend to the protector ply Radial or reinforcing ply Bias and vibration is acceptable the tire can be left in service Verify that tires have been properly mounted e For tubeless tires the red balance mark on the lower sidewall of the tire should be aligned with the wheel valve e For tube type tires the balance mark light spot on the lower sidewall of the tire should be aligned with the bala
10. as specified by the wheel manufacturer and install in the wheel groove or channel Be sure the O Ring is free of kinks or twists Position the previously inspected tire in front of the first wheel half If a bias tire lubricate the beads as required Slide the tire on the wheel MICHELIN AIRCRAFT TIRE When mounting tube type tires dust the tube and the inside of the tire with tire talc or soapstone before installing the tube This will prevent the tube from sticking to the inside of the tire or to the tire beads Dusting also helps the tube assume its normal shape inside the tire during inflation and lessens the chances of wrinkling or thinning from irregular stretching Caution Use care not to damage tube when mounting 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 the optimum 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 General mounting instructions Tire Wheel Alignment for Balance The red balance mark the lower sidewall indicates the light point of the tire s balance Align this mark with the heavy point of the wheel In the absence of a
11. from properly seating O Rings themselves must be of the proper material as specified by the wheel manufac turer for the intended application and temperature conditions Inspect O Rings for cracking cuts or other damage Particular attention should be given to permanent deformations in the O Ring O Rings found with deformations should be replaced Proper sealing of the wheel halves is critical in providing trouble free service e Should the inspection used O Ring for its integrity not be practical or manageable replace with a new O Ring with each tire change PACKING INNER WHEEL HALF ASSEMBLY FIXTURE TIE BOLT p Ness WASHER TIRE Tires Before mounting any tire verify that the tire is correct for the intended application Use the following checklist e Check that the tire markings are correct for the reguired application size ply rating speed rating part number TSO marking Visually inspect the outside of the tire for Damage caused by improper shipping or handling of the tire Cuts tears or other foreign objects penetrating the rubber Permanent deformations Debris or cuts on the bead seating surfaces Clean the tire bead surfaces with either a clean shop towel a soap water solution or with denatured alcohol as may be necessary Bead distortions Cracking that reaches cords Position Light Spot May Be Stamped On Wheel OUTER WHEEL HALF ASSEMBLY
12. radial is exposed for more exposes the reinforcing or than 6 1 0 s in protector ply more than 6 cm 1 0 sq in Casing Outer Ply serviceability criteria Casing Outer Ply Peeled Rib Bias Tire Casing Outer Ply Cracking and Contamination Bias Tire Peeled Rib Note Authorization is given Contamination Remove from service if the to return to maintenance base From Hydrocarbons reinforcing ply bias or protector lt 6 flights to replace tires Oil grease brake fluids solvents ply radial is exposed meeting the above criteria etc can soften or deteriorate if there is no continuous rubber components Groove Cracking cracking exposing textile Immediately upon contact with a Remove from service if the groove greater than 25 mm 1 inch hydrocarbon substance wash the cracking exposes the reinforcing in length contaminated area first with ply or the protector ply for more denatured alcohol then with a than 6 mm 1 4 in length Rib Undercutting soap and water solution By Remove from service if pressing the rubber surface in the undercutting extends more than contaminated area versus the 6 mm 1 4 under the rib adjoining uncontaminated area determine whether the rubber has become softened or spongy If so remove the tire from service Abrasion 8 Reverted Rubber MICHELIN AIRCRAFT TIRE Skid Burn Radial Tire Protector Belt Plies Casing Outer Ply
13. thus forming the PLY TURN UPS FOR BIAS constructed tires the carcass plies are laid at angles between 30 and 60 to the centerline or direction of rotation of the tire Succeeding plies are laid with cord angles opposite to each other to provide balanced carcass strength FOR RADIAL constructed tires each carcass ply is laid at an angle approximately 90 to the centerline or direction of rotation of the tire Each successive layer is laid at a similar angle Radial constructed tires of the same size have fewer number of plies than do tires of a bias construction because the radial cord direction is aligned with the burst pressure radial force allowing for optimized construction The beads or bead wires anchor the tire to the wheel They are fabricated from steel wires layered together and can be embedded with rubber to form a bundle The bundle is then wrapped with rubber coated fabric for reinforcement Depending on the size and design application BIAS tires are constructed with 2 to 6 bead bundles 1 to 3 per side By contrast RADIAL constructed tires have 2 bead bundles 1 on each side regardless of tire size Cha trips are strips of protec tive ponies or rubber laid over the outer carcass plies in the bead area of the tire Their purpose is to pro tect the carcass plies from damage when mounting or demounting and to reduce the effects of wear and chafing between the wheel and the tire bead
14. whether a stored inflated tire is still airworthy Time should not be the measure by which a tire is classified unserviceable e Shop re inspection should be made with the assembly infla ted to the operational pressure level The entire exterior of the tire should be visually inspec ted for cracking due to ozone or ultraviolet attack damages or any other condition If the limits given in the chapter on Tire Serviceability Criteria have been exceeded dismount the tire from the wheel and return to the supplier Subject the assembly to the standard air retention test to verify that the assembly will still meet the criteria of no more than 5 pressure loss in a 24 hour period While in storage if the assembly inflation pressure was being maintained using compressed air deflate the assembly and re inflate with nitrogen per industry standards Having met each the above conditions return the tire wheel assembly to stock Note The criteria for re inspection of the wheel must also be determined before returning the assembly to service minimize the effects of ozone attack and where re inflation capability exists tire pressure may be reduced to a value below operational pres sure but not less than 25 of the operational pressure or 40 psi 3 bars whichever is less e Transportation of a serviceable aircraft tire wheel assembly should be in accordance with the applicable regulator
15. 51 On Aircraft Inspection With Tire Mounted 52 Removal Criteria Wear Water can affect traction 52 Typical Wear Conditions Normal Wear Overinflation Underinflation MICHELIN AIRCRAFT TIRE Worn Beyond Recommended Limits Flat Spotting Asymmetrical Wear Serviceability Criteria Limits For Tire Damages Tread Wear Tread Cuts Foreign Objects Sidewall Cuts Foreign Objects Serviceability Criteria Operational Conditions 63 Hard Landing Rejected Takeoff Off Aircraft Inspection With Tire Dismounted 64 A Systematic Approach to Tire Inspection Bias tires Radial tires Matching and Mixability of Dual Tires 66 Matching Tires 67 Matching Criteria Bias Tires Radial Tires New versus Retreaded Tires Mixability Bias Bias Radial Radial Bias Radial Observe Load and Inflation Recommendations Vibration and Balance 70 Proper inflation pressure Inflation is equalized Full growth Beads properly seated Flat spotting uneven wear Properly mounted Air trapped between tire and tube Tube wrinkled Wheel out of balance Condition of wheel Loose wheel bearing Gear alignment Worn gear components General Dismounting Instructions For Aircraft Tires 72 Removal From Landing Gear 73 Reason for removal Tracking 73 Tire Dismounting 73 Tire Wheel Dismounting Sequence Tire Dismounting Equipment 75 Retreading and Repairing Aircraft Tires 77 Retreading Aircraft Tires 78 Acce
16. General mounting instructions for aircraft tires Emergency Pressure Retention Procedure Tire Wheel Assembly Within 30 minutes f bubbles are found on wheel hardware or a stream of bubbles at tire vents If no bubbles are found at plugs valves O rings or no stream of bubbles at tire vents El After 12 hour storage period check inflation pressure Be sure that the ambient temperature of the tire wheel assembly has not changed by more than 3 C 5 E Options f inflation pressure is equal to or greater than gt 97 5 of the specified operating pressure accept the tire wheel assem bly for in service usage or line maintenance storage see Storage Section for recom mendations on line mainte nance storage Note Re inflate tire to the specified operating pressure e If inflation pressure is less than 97 5 of operating pressure inspect the assembly for leakage Use a soap solution on tire beads and other susceptible wheel components valves fuse plugs over pressurization plugs wheel half parting line etc Emergency pressure retention check The following procedure may be used to perform a pressure retention check on a newly mounted tirelwheel assembly when If gt 9096 gt Accept Assembly time does not allow the basic procedure to be If 90 If soap bubbles or leaks are found make appropriate repairs Proceed to step 6
17. OR TYPE DESIGNATION QUALI FICATION Un DIN 026 LOAD RATING 9 MOLDED SKID O 0 PLY RATING 0 SPEED RATING g EOUIPMENT IDENTIFICATION 2 d A een SERIAL NUMBER CODE 5 000N0L29 V AEA CODES COUNTRY OF ORIGIN SIZE DESIGNATION 1 AEA Association of European Airlines aie ak TRADEMARK gt SERIAL NUMBER CODE MOLDED SKID FAA QUALIFICATION STANDARD DGAC QUALIFICATION STANDARD EQUIPMEN IDENTIFIC TYPE NUMBER CODE ue IDENTIFICATION LOAD RATING 6 PLY RATING COUNTRY OF ORIGIN du Ces M T CONSTRUCTION onroro w N AC SIZE 22 9 7 DESIGNATION DESIGNATION S313g8nL PART NO e SPEED RATING TUBELESS DESIGNATION 1 DGAC Direction G n rale de l Aviation Civile 2 FAA Federal Aviation Administration 3 All MICHELIN aircraft radials are tubeless s d mU TRADEMARK SERIAL NUMBER CODE IDENTIFICATION OTR NO CUT LIMITS Application is program dependant COUNTRY OF ORIGIN SCD NO OR MS OR OEM SPECIFICATION NO OR USAF NO TUBELESS OR TUBE TYPE DESIGNATION ONI d Op CODE IDENTIFICATION NO pen OW a 2 899 9 NATIONAL OR NATO Ge ee STOCK
18. airport check and readjust to operating inflation pressure PN prior to the next flight In all other cases maintain the inflation pressure per the standard recommendation Inflation oressure maintenance Schedule and action Measured Pressure as Yo of Operating Pressure More than 105 105 100 100 95 Continued on page 45 When to Check e Frequency Tires in service should have their cold inflation pressure checked daily to properly maintain operating pressures For aircraft operating on a less frequent basis inflation pressure should be checked before each flight When installed the TPIS Tire Pressure Indicator System can be used to make the daily inflation pressure check provided the TPIS indicators are verified against a calibrated pressure gauge at each aircraft A check Understand that tires are capable of retaining pressure to tolerances which will keep them well within 5 of the specified pressure each day Since pressure losses due to other causes can seriously affect performance and safety it still remains a recommended practice to verify the pressure value at least daily Tire Condition Overinflated Course of Action Because of variations in ambient temperature gauge accuracy etc caution should always be shown before adjusting an overinflated pressure e It is recommended that the first overinflated reading be recorded in the aircraft log along with the am
19. as that experienced in an aircraft rejected takeoff Tires that are heavily oil soaked Tires that have experienced a major pressure loss Repairable aircraft tires The following are acceptable when retreading aircraft tires Tread Area The size of cuts and or other tread injuries that can be repaired during retreading is dependent on many factors including the injury s length depth and width as related to the tire size itself The number and size of a repairable injury is also dependent on the retreader s repair methods and validation If specific details on repair limits are needed see your Michelin retreader Bead Area Minor injuries to the bead area may be repaired provided the carcass plies are not damaged e Innerliner Innerliner surface damage may be repaired bias tires The size of a repairable injury is dependent on the retreader s repair methods as well as government regulatory documentation MICHELIN AIRCRAFT TIRE Sidewall Rubber Surface defects on large commercial tires may be repaired provided the repair is at least 1 inch from the bead heel and no greater than an area 11 2 inches 50 mm by 4 inches 100 mm and does not penetrate or damage the carcass ply ting tips Operating and handling tips for better tire service Optimized tire performance is directly related to the use and care the tire is given While the single most importan
20. balance mark align the tire s Serial Number with the heavy point of the wheel main landing gear position tires only Many wheel manufacturers today identify either the light spot or heavy spot of the wheel with markings in the flange area Follow their instructions on assembly and balance Be sure to align the tires light spot 180 from the wheel s light spot or directly in line with the wheels heavy spot In the absence of specific wheel markings align the tire s red balance mark with the wheel inflation valve Some aircraft tubes feature balance marks to indicate the heavy portion of the tube These marks are approximately 1 2 wide and 2 long When inserting the tube in the tire its balance mark should be aligned with the balance mark on the tire If the tube has no balance mark align the valve with the balance mark on the tire for aircraft tires EN p mark A properly balanced tire wheel assembly improves the tire s overall wear characteristics In addition to severe vibration an unbalanced assembly will cause irregular and localized tread wear patterns that can reduce the overall performance life of the tire Be sure that nuts washers and bolts are installed in proper order and that the bearing surfaces of these parts are properly lubricated as required Tighten to manufacturer s recommended torque values After the tire is mounted on the wheel the assembly should be placed in a safety ca
21. dual tires diameter size standard established by either The Tire and Rim Association or The European Tyre and Rim Technical Organization e Radial Radial e Radial tires can be mixed on the same axle or bogie if the following requirements are met The tires are the same size designation All tires are qualified for the aircraft application All tires meet the size standards for overall diame ter and static loaded radius established by either The Tire and Rim Association or The European Tyre and Rim Technical Organization Bias Radial No specific rule can be applied for this case The mixability of bias and radial tires is determi ned by the airframer through aircraft testing In all cases airframer and airworthiness authorities recommendations must be followed Three possibilities exist Bias tires on the nose gear and Radial tires on the main gear or vice versa No effect on tire or aircraft performance unless otherwise specified by the airframer Mixing on a gear made up of bogies and dual mounts Any proposed mixing must be approved by the airframer Radial and Bias tires approved for the same application may be of dif ferent overall diameters when stood side by side It is important that the static loaded radius of the two tires be the same see figure above Contact the airframe manufacturer or tire manufacturer for static gt
22. extends the service life of a carcass several times past initial new tire usage FAA JAA Regulations require retreading and or repairing of aircraft tires to be performed in certified retread and repair stations by or under the responsibility of qualified certified technicians Repairs by unauthorized sources are not recommended Michelin meets or exceeds all testing requirements of the FAA or JAA for retreaded aircraft tires Retreading Aircraft Tires For aircraft tires the term retreading refers to the methods of restoring a used retreadable tire by renewing the tread alone or by renewing the tread plus the reinforcing ply s or protector ply Full recapping is the recommended procedure for tires with evenly worn tread tires with flat spotted tread or tires with numerous cuts in the tread area The new tread material extends around and over the shoulder of the tire for several inches Accepting Tires for Retreading Accepting tires for retreading requires careful inspection of all components of the tire Each individual tire is inspected by visual and air needle techniques prior to during and after the retreading process Shearography inspection can also be used to inspect for internal defects which may limit the retreadability of a carcass Retreading repairing aircraft tires Inspections must meet approved process limitations for that tire to be retreaded Repairing Aircraft Tires Many tire
23. of wearout will be near the centerline of the tire Follow wear removal criteria Casing Outer Ply Normal Wear Patterns Radial Tire Overinflation When a tire has been operated with a higher pressure than required for the aircraft loads an accentuated centerline wear will be apparent Overinflation has reduced the number of cycles to wearout and made the tire more susceptible to bruises cutting and shock damage Follow wear removal criteria Casing Outer Ply Effects of Overinflation Radial Tire serviceability Casing Outer Ply criteria Protector Belt Plies e Underinflation When a tire has consistently been operated underinflated shoulder wear will result Severe underinflation may cause ply separations and carcass heat build up which can lead to thrown treads sidewall fatigue and shorten tire life Follow wear removal criteria Effects of Underinflation Bias Tire Casing Outer Ply Effects of Underinflation Radial Tire e Worn Beyond Recommended Limits Tire has been worn beyond acceptable limits and into the top belt plies top carcass plies for bias not shown Tire is not retreadable Tread Reinforcing plies Casing Outer Ply Flat Spotting This tire wear condition is a result of the tire skidding without rotating i e brake lockup or large steer angle Tire should be removed from service if the flat spottin
24. rubbing against the wheel If damaged dismount the tire and replace the tube or valve e Check the fuse plugs or pressure relief plugs with a soap and water solution If bubbles appear replace the valve core and recheck e Inspect the tread and sidewall areas for FODS cuts snags etc Check suspected areas with a soap solution If bubbles appear the tire must be dismounted and repaired by a gualified repair station scrapped e Totally immerse the tire wheel assembly in a water bath If a water bath is not available apply a soap other leak detector solution to the entire tire wheel assembly The appearance of bubbles at any point other than at the vents in the lower sidewall of the tire just above the wheel flange will indicate a leak Note that nitrogen will diffuse through the sidewall vents for the entire life of an aircraft tire Look closely for bubbles in the tubewell area of the wheel to be sure nitrogen is not leaking from any fatigue cracks or at the O Ring seal of the wheel halves e If no leak source other than the sidewall vents can be found it will be necessary to dismount the tire and make a further inspection Inflation oressure maintenance 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 m
25. the airframe manufacturer for each aircraft configuration is necessary to carry the load of the aircraft This pressure value is therefore needed regardless of the ambient temperature For example if PN 12 bars 175 psi this is the pressure needed at any ambient temperature Note Do not reduce the pressure of the cold tire subjected to frequent changes in ambient temperature Refer to P 44 for additional guidance Aircraft experiencing large ambient temperature differences between airports Large temperature differences place a special burden on aircraft operations As can be seen in the chart above large changes in ambient temperature will result in corresponding changes in gauge pressure Aircraft flying long distances where a large gt 30 C 54 F decrease in ambient temperature will occur need to apply specific inflation maintenance procedures One of two options should be selected in this situation e In the event that pressure main tenance is not available at the destination airport raise the ope rating inflation pressure PN by 1 for each 5 3 temperature drop relative to the departure air port to insure adequate inflation pressure in the assembly at the destination airport Note Do not exceed maximum rated loaded tire pressure MICHELIN AIRCRAFT TIRE 211 202 194 185 176 Units in F and PSI Or e When pressure maintenance is available at the destination
26. tire is no longer safe to use and must be replaced Inflation oressure maintenance Severe underinflation may cause ply separation and carcass degradation because of the extreme heat the strain caused by the excessive flexing action or the occurrence premature standing waves see photo This same condition can cause inner tube chafing and a resultant blowout In dual tire applications underinflation of one tire causes the other tire to carry a disproportionate amount of load As a result both tires can be deflected considerably beyond their normal operating range potentially causing ply separations and or carcass degradation Effects of Overinflation Tires operating under too much inflation pressure are more susceptible to bruising cuts and shock damage Ride quality as well as traction will be reduced Continuous high pressure operation will result in poor tire wear characteristics center wear and reduced landings performance Standing Wave in Laboratory conditions 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 thi
27. 1 8 of the circumference on any part of the tread or e If either the protector ply radial or the reinforcing ply bias is exposed for more than 1 8 of the circumference at a given location Note Tires reaching this wear point on an aircraft at a remote Station can make a return to base flight s under standard operating conditions without sacrificing retreadability of the casing Note In some military applications the removal point of a tire is indicated by a red fabric cord built into the tire or a wear depth plug Belt Plies Casing Outer Ply Wear Removal Criteria for Retreadable Radial Tire Water can affect traction The accumulation of water on runway surfaces can affect wet traction Its affect is dependent on a number of factors including water depth aircraft speed and runway surface conditions The most effective method to minimize the affects of water on traction is to reduce water depth or allow the water to escape from under the footprint more rapidly Many airport authorities today have adopted cross grooving for their runway surfaces which allows for rapid drainage of water MICHELIN AIRCRAFT TIRE Casing Outer Ply Normal Wear Patterns Bias Tire Casing Outer Ply Effects of Overinflation Bias Tire Protector Belt Plies Typical Wear Conditions e Normal wear When tire wear has been optimized from proper maintenance and inflation pressures the first point
28. Tire of any cut Note Tires removed for tread cuts or other injuries should be sent to a certified repair station to be repaired and retreaded or scrapped MICHELIN AIRCRAFT TIRE Embedded objects take all forms serviceability criteria Casing Outer Ply Separations Bias Tire Mark all cuts foreign objects Caution Do not probe objects while Bulges or separations damages or leaks while tire is tire is inflated Immediately remove the tire from inflated Use a light colored service Mark these areas with a crayon wax marker or paint stick color crayon before deflating Damages can be difficult to find when a tire is uninflated MICHELIN AIRCRAFT TIRE 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 1 Chevron Cutting exposing textile can be left in service Continue in Ser vice if Protector Belt Plies Casing Outer Ply X Cutting penetrates the tread to a level Tread Chipping Chunking Radial Tire less than one half the molded skid depth even if the surface exhibits some shallow chipping or Chevron Cutting Bias Tire chunking Chevron Cutting Tread Chipping Chunking Remove from service if the Remove from service if the chevron cutting results in reinforcing ply bias or protector chunking which extends to and ply
29. actors are conducive to hydroplaning removal criteria should be adjusted accordingly Contact Michelin for detailed information Landings per tread Tire performance can be improved by using slow taxi speeds and by letting aircraft roll during landing and by avoiding hard braking Whenever possible make large radius turns which minimize tire scrubbing e Michelin Aircraft Product Line e Studio graphique Michelin e Gris souris Air Bourget Boeing Gajic Mc Donnell Douglas Michelin Sirpa Air Gauthier Trebosc Imprimerie Fabr gue Headquarters Michelin Aircraft Tyre 23 place des Carmes D chaux m R tread Service Centers Research amp Developmeht Charlotte U S A Bourges France P Studio graphigue bs 63040 Clermont Ferrand Cedex 9 France 5 Greenville U S A Cuneo Italy Tel 33 0 4 73 32 76 40 Fax 33 0 4 73 32 76 42 4 Ladoux France Kansas City U S A M Nong Khae Thailand Commercial Offices Nbrwood U S A 72 lt North Central and South America j VB gt Michelin Aircraft Corporation Manufacturing rr AUI 1 Plants ij tC 1305 Perimeter Road i c Greenville SC 29605 United States Bourges France Tel 1 864 422 7000 Fax 1 864 422 7071 Nong Khae Thailand ET Europe Middle East and Africa Norwood 7U A un Michelin Air
30. and it is possible to determine if a tire is cool or not Inflation Pressure psi 1 loss rate 3 loss rate 5 loss rate 40 50 60 Time days Note that operating pressures whether loaded or unloaded are specified for cool tires e The maximum allowable pressure loss for a tire is 5 for any 24 hour period Pressure loss Normal Response The maximum daily pressure loss for a tire wheel assembly is 5 The graph above shows how the normal pressure of a tire wheel assembly can change with time even when no disruption in the sealing system exists It demonstrates the importance of checking pressure when mounting a new assembly on the aircraft MICHELIN AIRCRAFT TIRE 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 e Check that the valve core is not leaking Apply a small amount of soap solution on the end of the valve stem If bubbles appear replace the valve core and recheck Be sure that the valve stem threads are not damaged Otherwise the valve core and the valve cap will not fit properly Each valve should have a valve cap on it to prevent dirt oil moisture and other contaminants from getting inside and damaging the core Be sure that the valve is not bent or
31. and such a tire is fit for service and can be retrea ded e Damage blisters or separa tions of the chafer strips are repairable Send the tire to an authorized repair station e If carcass cords under chafer strip are damaged the tire should be discarded For Radial Tires If bead area wear along the wheel flange exceeds 1 mm 1 32 remove the tire from service f protruding bead wires bead wire separations or badly kin ked beads are found the tire should be discarded Inspect the Tire s Innerliner e As with external areas any tire with loose frayed or broken cords inside should be discarded e Liner blisters especially in tubeless tires should be left undisturbed Do not pierce puncture or cut them To do so will destroy the air retaining ability of a tubeless tire e Generally confirm the good condition of the innerliner e g no wrinkles Tube Inspection When inspecting tubes do not inflate them with more pressure than is required to simply round out the inner circumference of the tube never more than 1 psi Carefully inspect the inflated tube for leaks First visually and then by submersion in water MICHELIN AIRCRAFT e Examine the valve stem for leaks signs of valve pad separation and bent or damaged valve stems e Inspect the tube for severe wrinkles or creases Remove from service if any are found Wrinkles are evidence of improper fitt
32. as 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 area of the tire in contact with the ground Most Michelin tires are designed with circumferential grooves molded into the tread area These provide a mechanism to channel water from between the tire and runway surface which helps to improve ground adhesion The tread compound is formulated to resist wear abrasion cutting cracking and heat buildup It prolongs the life of the casing by protecting the underlying carcass plies The undertread is a layer of specially formulated rubber designed to enhance the bonding between the tread reinforcement protector plies and the carcass body For those tires designed to be retreaded this rubber layer will be of sufficient thickness to act as the interface for buffing the old tread assembly as well as the liaison with the new retread products A carcass ply consists of fabric cords sandwiched between two layers of rubber Today the most common fabric cord is nylon The carcass body itself is made from multiple layers of carcass plies each one adding to the strength and load bearing capability of the tire The carcass plies are anchored by wrapping them around bead wires
33. at 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 manujacturers 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 e Rolling tires on the floor and using mechanical lifting equipment to avoid possible back injuries e Inspecting tires and wheels in advance for possible shipping damage Inflating e When inflating tires be sure to use a Suitable inflation cage Recommended Angle of Approach e Keep pressure hose and fittings used for inflation in good condi tion e Allow the tire to remain in the inflation cage for several minutes after reaching full inflation pressure e Respect inflation pressures and all other safety instructions Tires in service e Careful attention should be shown to tire wheel assemblies being handled or in storage e Never approach a tire wheel assembly mounted on an aircraft that has an obvious damage until that tire has cooled to ambient temperatures allow at least 3 hours e Always approach a tire wheel assembly from an oblique angle in the direction of the tire s shoulder e Deflate tires before removing them from the aircraft unless the tire wheel assembly is to
34. be immediately remounted on the aircraft such as with brake MICHELIN AIRCRAFT TIRE inspections Deflate tires before attempting to dismount the tire from 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 the valve stem e The transportation of a service able aircraft tire wheel assembly should be in accordance with the applicable regulatory body for the airline Transportation of a serviceable inflated aircraft tire is covered by the U S Department of Transportation Code of Federal Regulations the International Air Transport Association IATA and other regulatory bodies e While serviceable tires may be shipped fully pressurized in the cargo area of an aircraft Michelin s preference is to reduce pressure to 25 of operating pressure or 3 bars 40 psi whichever is the lesser e Remove from service tire wheel assemblies found with one or more tie bolt nuts missing Storage Tire can be lifted through center Tires are designed to be tough durable 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 0 C 32 F are not objectionable room temp
35. ber continue in service e If sidewall cords are exposed or damaged remove the tire from service Bulge Blister Separation Remove the tire from service Tire Cut Typical Ozone cracking Weather Ozone Cracking Remove from service only if weather or ozone checking or cracking extends to the cords Important Weather checking or cracks that do not reach the carcass cords are not detrimental to tire performance and do not constitute cause for removal Tires showing only surface cracking can be left in service Serviceability Criteria Operational Conditions e Hard Landing After a particularly hard landing tires wheels brakes and landing gear systems should be visually inspected for damage Inspect the tires for any obvious signs damage such as cuts splits in the rubber flat spotting tread chunking bulges etc For damages follow the guidelines given under Serviceability Criteria Limits For Tire Damages If no damages are noted the tire s should be left in service It is recommended that an entry of the landing be made in the aircraft log as a future reference Some tire damages such as bottoming the tire may not become apparent until several landings later e Rejected Take off Aircraft experience various levels of rejected takeoffs Not all rejected takeoffs are severe enough to warrant automatic tire removal The following guidelines are recommended e Where airc
36. bient temperature After the 2nd confirmed reading gt 5 readjust tire pressure to maximum of normal operating range Normal Operating Pressure Range Do not adjust tire pressure Do not exceed tire s maximum rated pressure value loaded nor the wheel s TSO qualification pressure value Ioaded Acceptable Daily Pressure loss e Checking Hot Tires Knowing if the pressure of a hot tire is correct is nearly an impossible task The air in a hot tire expands causing a temporary higher pressure reading The exact temperature is not known and thus the relative pressure is also unknown As the tire cools its pressure is also changing and will continue to do so until ambient temperature is reached A hot tire is one that has dynamically rolled under load on the aircraft and has not been allowed to reach ambient temperature not been allowed to cool for at least three hours Tires at elevated temperatures will develop inflation pressures higher than the specified cold inflation pressure Readjust tire pressure to maximum of normal operating pressure range 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 e flight schedules make it impossible to make a routine pressure check a cool tire tire is continually exposed to direct sunlight While no precise procedure can be gi
37. can be determined for the tire wheel assembly by applying a soap and water solution to the entire assembly or by immersing the tire wheel assembly in water For a Dismounted Assembly check wheel for X XK XK X XXXXXX E Ld E erviceability e ire serviceability criteria serviceability criteria i Casing Outer Ply Wear Removal Criteria for Retreadable Bias Tire A simple easy to perform series of inspection procedures can prevent minor incidents from developing into major problems and help to optimize tire performance Regular inspection is a small price to pay to protect your valuable tires and the safety of your aircraft and the people it carries Note If an aircraft has made an emergency or particularly rough landing the tire tube and wheel should always be checked On aircraft inspection with tire mounted Removal Criteria Wear The tread area of the tire should be visually inspected for any damage and the state of tread wear Removal at the right time will optimize tire wear while still protecting the life and investment of the carcass In the absence of specific instructions from the Airframer Operations Manual Service Bulletins etc a tire should Protector Ply be removed from service for wear using the following criteria Based on the fastest wearing location remove tires e When the wear level reaches the bottom of any groove along more than
38. commended prior to take off An aircraft that is to remain idle for a period longer than three days should either be moved every 72 hours or blocked up so that no weight is on the tires Aircraft in storage out of service for more than 14 days should be blocked up so that there is no weight on the tires Chevron Cutting Cross cutting runways is common at many major airports around the world It improves drainage reduces the danger of standing water and thus decreases the risk of hydroplaning However the sharp edged ridges of concrete that result can cause chevron type cutting of the tire tread ribs particularly on the high pressure tires used on jet aircraft Chevron cutting occurs during aircraft touchdown at spin up As the tire begins to accept aircraft loads deforms slightly in these cross grooves At the same time rapid acceleration is occurring The forces reguired to accelerate the tire to ground speed cause a tearing action which forms the chevron These cuts are at right angles to the ribs and rarely penetrate to the fabric tread reinforcement ply or protector ply Refer to the section on Tire Serviceability Criteria for handling this condition Hydroplaning This condition results when on a wet runway the tire s tread is progressively lifted off the runway surface A wave of water builds up in front of a rolling tire allowing the tire to ride on the water and lose contact wit
39. commended that Tire dismounting removal information accompany Deflate any non serviceable damaged the tire to the repair station or Proper dismounting procedures tire wheel assembly before dismounting retreader The simplest approach is simplify the job of servicing aircraft from the aircraft Worn serviceable to use a tag or label attached to the tires while increasing safety and units may be left inflated tire with a self sticking adhesive reducing the chances of damaging applied to lower sidewall or by use tires or wheels The task of Reason for removal Tracking of heavy or nylon string dismounting tires should not be undertaken without proper In order to properly track reasons for Caution Do not use staples eguipment instructions and trained tire removal and to take appropriate or other metal devices for affixing personnel action it is very important to have tags or labels to tires or inner tubes accurate information regarding tire Keep adhesive labels above the bead Careful attention must be given to removal This information helps the area of the tire disassembling and handling wheel retreader repair station to make components to avoid damage to decisions concerning inspections and A sample label is shown above critical surfaces To assist in this the future use of the tire process wheel manufacturers publish specific instructions in their maintenance and overhaul manuals Follow their recommendations and procedures to ass
40. craft Tyre U 23 place des Carmes D chaux 63040 Clermont Ferrand Cedex 9 France lt Tel 33 0 4 73 32 76 36 Fax 33 0 4 73 32 76 44 www michelin com aviation E A East ant Oceania A d Michelin Aircraft Asia _O_ Tower 12th Floor 252 Phaholyothin Road Samsaen Nai Payathai Bangkok 10400 Thailand LE Tel 66 2 619 3530 Fax 66 2 619 3069 MICHELIN d M 7 d d
41. delivered to a line maintenance station as an airworthy replacement unit may be stored at full operational pressure for up to 12 months see comments in the section on tire mounting found later in this manual The following storage handling conditions are strongly recommended to minimize the damaging effects of ozone MICHELIN AIRCRAFT TIRE e Inside a warehouse away from direct sunlight or precipitation Wet or moist conditions can carry other chemicals which can have a further damaging effect on tires Storage Area Environment e Temperatures should remain between 0 C 32 F and 40 C 104 E Use reasonably low intensity lighting sodium vapor lamps are preferred e Environment should be free of strong air currents and excessive dirt Ozone Sources Store away from fluorescent lighting mercury vapor lamps electric motors battery chargers electric welding equipment and electric generators Tire Storage e Stand the tire such that it rests on its tread whether on the floor or in a rack e This orientation should be used for any tire which will be held in storage for more than 1 months time Storage racks should provide an adequate amount of surface area to support the tire to prevent a distortion or set from occurring in the tread area e If high ozone concentrations can be reduced or eliminated each tire should be protected by appro
42. e added resistance to the cutting and tearing action associated with chevron cutting Radial Tire Construction Products unigue to the radial tire The protector ply is typically found in retreadable tires and placed in the crown area just below the tread rubber It provides cut resistance protection to the underlying belts and carcass plies Belt plies are laid between the tread area and top carcass ply They restrain the outer diameter of the tire providing a tread surface with greater resistance to squirm and wear as well as providing a more uniform pressure distribution in the footprint for improved landings performance Hu u AAA Chine tires The chine tire is a nose wheel tire designed to deflect water and slush to the side and away from intakes on aft fuselage mounted jet engines It consists of a flared upper sidewall protrusion which deflects the spray pattern of water or slush displaced by the tire s contact with the runway A tire can have a single chine one sidewall flared for dual nose wheel tire configurations or double chines both sidewalls flared for single nose wheel tire configurations MICHELIN AIRCRAFT TIRE Dual Chine Tire mr The chine tire is now in use as standard eguipment on many commercial jets It is fully retreadable and may be used on any aircraft provided adeguate clearance is available TRADEMARK PART NO TUBELESS
43. ed closer to the window Fluorescent or mercury vapor lights should not be used because they generate ozone Low intensity sodium vapor lights are recommended See the section on Ozone for more information Stores tires vertically Whenever possible tires should be stored in regular tire racks which hold them up vertically The surface of the tire rack on which the weight of 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 tires is not recommended If tires are stacked horizontally they may become distorted resulting in mounting problems This is particularly 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 with the wheel during initial inflation Tires which are stacked on top of each other sidewall to sidewall have increased stresses in the tread grooves If tires are stored for an extended period of time or in an environment with high ozone concentration ozone cracking is most likely to form in the tread grooves If tires must be stacked they should not be stacked for more than 6 months maximum The maximum stacking height e tires high if tire diameter is greater than 40 inches 1 meter e 4 tires high if tire diameter is less than 40 inches inches 1 me
44. ed paint dot Simply apply a soap solution to these vent markings The appearance of small bubbles will indicate diffusion This bubbling is normal and may be seen at any time while the tire is inflated Maximum allowable diffusion is 5 for any 24 hour period Pressure losses in excess of 5 may indicate leakage from other sources In that case the tire and wheel assembly should be carefully tested for leaks preferably by total immersion before placing it into service If no assembly leaks are found dismount and have the tire inspected by the manufacturer or a qualified repair shop MICHELIN AIRCRAFT TIRE Note Do not identify a tire as a leaker solely on the rate of bubbles from these vent holes A high rate of bubble venting is not always an indicator of tire leakage It is best to judge excessive leakage of a tire wheel assem bly based on pressure loss as measured with a calibrated gauge preferably the same gauge used to initially inflate the tire Not all aircraft tires are vented Improvements in materials tire design and fabrication make the need for lower sidewall venting unnecessary for all aircraft tires This is particularly true for the physically smaller tires such as General Aviation and High Performance Military tires Knowing which tires have been vented is important Tires requiring lower sidewall vents will have either a green or white paint dot applied to the area of each vent hole Tires
45. eel or wheels the tire is scrubbed with great force against the pavement A small rock or debris that would ordinarily cause no damage can virtually be screwed into the tire This scuffing and grinding action takes off tread rubber and places a very severe strain on the sidewalls and bead areas of the tire at the same time Making wide radius turns will reduce tread rubber removal and sidewall stresses Condition of Airport Field Regardless of preventive maintenance and the care taken by pilot and ground crew tire damage is almost certain to result if runways taxi strips ramps and other paved field areas are in bad condition strewn with debris or poorly maintained i e Chuckholes pavement cracks or step offs in the pavement can all cause tire damage In cold climates especially during winter all pavement breaks should be repaired immediately Accumulated debris on paved areas including hangar floors is especially hazardous Stones and other foreign material should be kept swept off all paved areas Special attention should be paid to make sure that tools bolts screws rivets and other repair materials are not left lying on an aircraft so that when it is moved they fall to the floor If a tire rolls over such material it can result in punctures cuts or complete failure of the tire and tube Avoid Chemical Contamination Chemicals and hydrocarbons such as jet fuel hydraulic fluids grease cleaning age
46. eratures above 40 C 104 are detrimental and should be avoided Handling aircraft tires Care should be shown when hand ling aircraft tires While tough and durable tires can be damaged or cut by sharp objects or if excessive force is used Avoid lifting tires with conventional two prong forks of material handling trucks Damage to bead mounting areas or the innerliner can occur A wide flat pincher type fork assembly of the type that lifts the horizontal tire by squeezing against the tread surface is recommended An alternate recommended method would be to use a rounded bar to lift the tire through the center Avoid the use of forks or other objects which have corners that could damage the bead surfaces When possible handle tires by lifting or rolling Avoid moisture and ozone Ozone What is it Ozone is a gas a form of oxygen In the earth s atmosphere where it occurs naturally in small amounts ozone plays a crucial geophysical role because of its intense absorption of solar ultraviolet radiation Additional ozone created when industrial exhaust mixes with ultraviolet rays can be harmful Ozone degrades organic matter such as rubber Impact of ozone on tires Most of the natural and synthetic elastomers used in aircraft tires are susceptible to ozone attack Ozone in the air readily reacts with the double bonds unsaturation in the rubber molecules The result of this reaction is the breaking o
47. etrate between the tire and wheel Note Do not use hydrocarbon based lubricants These can be harm ful to the rubber components of the tire e Reapply a reduced hydraulic pressure to the tire e Repeat several times if neces sary If the tire still remains fast Remove the tire wheel assem bly from the machine Reinflate the tire in a cage until the bead moves back to its correct position Deflate the tire Recommence the dismounting MICHELIN AIRCRAFT TIRE 4 100 TRAVEL 0 4 10 RADIAL CLEARANCE ADAPTOR RING Ring type bead breaker procedure following the same procedure Note Cases of bead roll over should be reported to the retreader who will examine the tire for damage A tire found to have been damaged should be scrapped e Remove tie bolts and slide out both parts of the wheel from the tire e For tube type tires remove the tube e Tire is now dismounted 75 Tire Dismounting Equipment The primary component for dismounting an aircraft tire from its wheel is the bead breaking equipment used to loosen the tire from the wheel bead seats Two types of bead breaking equipment can be identified here e The ring type bead breaker Bead breaking is performed by pushing a movable adapter ring against the lower sidewall of one side of the tire The opposite side consists of a stationary adapter ring that also contacts the lower
48. f MICHELIN AIRCRAFT TIRE Typical ozone cracking molecular bonds and a degradation of the rubber which lead to crack initiation Continued stress and especially cyclic stress causes the crack to grow until it is visible as the characteristic surface crack perpendicular to the direction of the applied stress Designing for ozone To aid in the control of ozone attack on rubber the tire materials specialist adds waxes and protective chemicals Some of these ingredients address ozone attack when the tire is ina static state at room temperature other ingredients are activated by heat and protect the tire once it is in service Further the tire designer is mindful of the impact of shapes and contours on stress concentrations Still steps need to be taken in storage to delay the effects of ozone attack Wet or moist conditions have a deteriorating effect on tires and tubes and can be even more damaging when the moisture contains foreign elements that are further harmful to rubber and cord fabric Storing aircraft tires E i E 8 E ES P i i 5 L i Strong air currents should be avoided since they increase the supply of oxygen and quite often carry ozone both of which cause rapid aging of rubber Particular care should be taken to store tires and tubes away from fluorescent lights electric motors battery chargers electric welding equipment electric generators and similar elec
49. g exposes the protector ply radial tire or reinforcing ply bias tire f flat spotting does not extend to the protector ply or reinfor cing ply the tire can be left in service If the localized loss of rubber results in aircraft vibrations even though no fabric has been exposed the tire must be removed from service MICHELIN AIRCRAFT TIRE lt Outer Ply NS Worn Beyond Limits Radial Tire Belt Plies Casing Outer Ply Asymmetrical Wear Radial Tire Tire Flat Spot Bias Tire e Asymmetrical Wear The tire has been operated under prolonged yaw and or camber This camber angle can be induced through landing gear or undercarriage deformation or manufacturer s settings tolerances Taxiing with one engine or high speed cornering can also cause asymmetrical wear In some cases low inflation pressure will contribute to this condition Tires that do not expose any fabric can be dismounted turned around and remounted to even up wear As long as standard wear criteria is met the tire should remain in service serviceability criteria Suggested approach 1 Tread 2 Sidewalls 3 Bead areas 4 Innerliner e Serviceability Criteria Limits e Tread wear For Tire Damages Check for typical wear patterns When assessing tire damages it is Follow removal guidelines given best to make inspections with the under the section Removal tire inflated Many damages t
50. ge In all cases all tires should be at least egual to or greater than the specified operating pressure Note If one tire has an abnormally high pressure gt 5 as compared to the other tires on that gear look for possible causes such as faulty brakes or incorrect pressure adjustment at previous check Checking and monitoring inflation pressure is usually performed on loaded tires Be sure to know whether the operating inflation pressure is for loaded or unloaded tire conditions Loaded inflation pressure is 1 04 x Unloaded inflation pressure Use an accurate calibrated gauge preferably with a dial type indicator Watch for changes in ambient temperature A 3 5 temperature change will result in a 196 tire pressure change Inflation oressure maintenance e When making tire pressure entries in the aircraft log book it is best to record the ambient temperature along with the pressure readings e recommended tracking system for daily pressure checks is to write tire pressure ambient temperature and date on the sidewall of each tire during pressure monitoring This method allows easy guick follow up on tire pressure conditions from line station to line station e Make sure tires have sufficient time to cool A cool tire is one at ambient temperature e Allow 3 hours after landing if not exposed to direct sun light for tires to properly cool By carefully using the palm of the h
51. ge for inflation with nitrogen It is recommended that the cage be placed against an outside wall that is strong enough to withstand the effects of an explosion of 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 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 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 require the use of nitrogen when inflating tires for aircraft above a specified Maximum Take Off Weight MTOW Michelin recommends the use of a dry commercial grade nitrogen of at least 97 purity when inflating all aircraft tires Nitrogen provides a stable inert inflation gas while eliminating the introduction of moisture into the tire cavity Aircraft operating proced
52. h the runway surface Loss of traction steering ability and braking action MICHELIN AIRCRAFT TIRE occurs This action is usually referred to as dynamic hydroplaning Its occurrence is a function of water depth and aircraft speeds The same phenomenon can result when a thin film of water on the runway mixes with the contaminants present or if the surface texture of the runway is smooth This is called viscous hydroplaning Generally the irregular condition of the runway surface is sufficient to break up this film Today most airport runways are designed to minimize water buildup Cross grooving is one example In addition tires have circumferential grooves which help to dissipate water An aircraft tire experiencing hydroplaning usually viscous hydroplaning may form an area of reverted rubber or skid burn in the tread This area will be oval in shape similar to a flat spot If the reinforcing ply or protector ply is not exposed the tire can remain in service Operating and handling tips for better tire service m e Note A similar reverted rubber tread condition can occur if the tire slides on ice for any distance Tire removal criteria should be based on operational and tire condition factors Factors to be considered are runway cross grooving tire footprint area number and remaining depth of grooves and level of runway flooding When operational and tire condition f
53. hat Criteria Wear are readily visible on an inflated tire can no longer be seen when that tire is uninflated Be sure to mark all damages with a chalk stick before dismounting a the tire Tires removed should be tagged with a Reason For Removal A Systematic Approach to Tire Inspection assures that all parts of the tire are properly inspected A recommended sequence of inspection is given above Casing Outer Ply Protector Belt Plies Casing Outer Ply Tread Cuts Foreign Objects Tread cut removal limits are at times given in specific documentation such as aircraft maintenance manuals 4 1 3 technical documentation airline operation manuals tire sidewall markings etc Follow specific guidelines when given In the absence of specific cut removal documentation tires should be removed when e Cuts embedded objects or other injuries expose or pene trate the casing cord body bias or tread belt layers radial e If a cut or injury severs or extends across a tread rib the tire should be removed from Service e Under cutting at the base of any tread rib cut is cause for removal Round foreign object openings are acceptable up to 9 5 mm 0 375 in diameter 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 Radial
54. he sidewall or shoulder areas of the tire particularly under landing stress or in the event the tire strikes an obstruction It can cause potential wheel damage Under the severe strain of an extra load the wheel may fail even before the tire does is important to use inflation pressures recommended by the airframe manufacturer for each tire Be sure to determine if loaded or unloaded inflation pressure is specified Loaded inflation pressure will be 4 greater than unloaded inflation pressure If tires are run at unequal pressures the tire with the higher inflation pressure will carry a greater share of the load even though both tires will be of the same deflection This higher shared load can reduce the safety factor and service life of the tire Tire pressures should be checked daily with an accurate gauge when the aircraft is engaged in more than one flight a day Otherwise pressures should be checked before each flight FT TIRE 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 bottle or canister The high pressure side should never be used The safety practices for mounting and dismounting aircraft tires detailed in this Manual must be followed
55. heels Improperly Torqued Wheel Tie Bolts Wheel Gouges and Scratches Corrosion or Wear on Bead Ledge Area Knurls Damaged Sealing Surfaces Wheel Assembly Holes Wheel Cracks e tube type wheel converted to tubeless application should have the knurls removed Leakage will show at the tire wheel contact area e Leakage through the well area of the wheel tubeless tires can occur from porosity or fatigue cracks particularly if fatigue life is exceeded Proper painting of the wheel should seal leakage from minor porosity e Damaged Wheel Sealing Surfaces or improperly machined sealing surfaces may cause slow leakage Correct irregularities before assembling the wheel Foreign material or heavy paint can impair the sealing surface e Damage to the tire innerliner tubeless tires e Small cracks or splits in the inner tube For a Mounted For a Dismounted Tire Wheel Assembly Assembly check tire check for and tube for In all cases be sure to account for x x x Troubleshooting Have You Considered The above pressure loss troubleshoo ting chart for tirelwheel 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 e Tire inflation pressure must be at operating or rated pressure when testing for points of pres sure loss e The point of leakage
56. hey equally share the weight carried by that landing gear assembly As airports grow in size and taxi runs become longer chances for tire damage and wear increase Internal tire heat buildup also can be of concern Speed length of rolling and stops are all important in MICHELIN AIRCRAFT TIRE influencing heat buildup A taxi speed of 40 mph for 35 000 feet is demonstrated during the TSO certification of a tire For either speeds or taxi distances greater than these limits a 5 10 minute pause is recommended before takeoff For less foreign object damage in taxiing all personnel should make sure that ramps parking areas taxi strips runways and other paved surfaces are regularly cleaned and cleared of all objects that might cause tire damage Pivoting By Using Brakes Increased airport traffic and longer taxi runs are subjecting tires to more abrasion from turning and pivoting while braking Severe use of brakes under pivoting conditions can wear flat spots on tires and cause them to become out of balance making premature retreading or replacement necessary Pivoting on surfaces with heavy texture or a step condition can Operating and handling tips Tor better tire service locally tear the tread from the casing This tear may not show as a separation until later in the tire s service life Careful pivoting of an aircraft also helps prolong tire tread life When an aircraft is turned by locking one wh
57. ing Procedure the Tire Wheel Assembly Alternate Pressure Loaded versus Unloaded Tires Retention Check 32 Properly Inflating Tube Type Tires Procedure Effect of ambient temperature Sidewall Venting 33 on gauge pressure 42 Not all aircraft tires 2 Inflation Standard are vented 33 for Maintaining Pressure Level Storage of an Inflated Tire Aircraft experiencing large ambient and Wheel Assembly 34 temperature differences between airports Mounting Tire W heel Schedule and action 44 Assembly When to Check On The Aircraft 36 Frequency Checking Hot Tires Visually Inspect Compare tire pressures on the Tire Wheel Assembly 37 same given landing gear Readjust Tire Pressure 37 Single and Multiple tire gear Two Tire Gear Inflation Pressure Three or more tire gear Maintenance 38 Monitoring Inflation Pressure What To Do Proper Inflation Getting 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 Serviceability Criteria
58. ing year example 9 for 1999 3 numbers indicating the manufacturing day in Julian calendar example the tire was manufactured the 211th day of the year Code letter related to the facility and the decade see table below Unique production identification number Bias Serial Number Definition 9 2 1 1 P 0 0 0 2 5 N A N Last number of the manufacturing example 9 for 1999 3 numbers indicating the manufacturing day in Julian calendar example the tire was manufactured the 211th day the year Code letter related to the facility and the decade see table below Unigue production identification number Letter signification The letter code in the tire serial number is used to identify both the manufacturing facility and the decade manufacture It follows the rules below ARA Through From Jan 01 1996 to from Jan 01 2000 to Manufacturin Aa Mail Dec 31 1995 Dec 31 1999 Dec 31 2009 acilit included included included Bourges Clermont Ferrand Greenville Nong Khae Norwood T de LUm E In the event of conflict between recommended procedures be sure to contact your Michelin representative before undertaking the procedure in guestion Aircraft 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 th
59. ing of the tube within the tire Where wrinkles exist chafing takes place and that can result in loss of air or a blowout e Inspect tubes for evidence of chafing by the toes the tire beads If chafing exists remove the tube from service and scrap e Examine for thinning Where the heat is greatest the tube has a tendency to be stretched over the rounded edge of the bead seat of the wheel This is one of the reasons why when mounting tubes should always be inflated until the tire beads are in position then completely deflated and reinflated to the final pressure The stretch on the tube is then egualized throughout its inner and outer periphery Also check tubes for possible thinning out due to brake drum heat in the area where they contact the wheel bead toes The set or shape of the tube will help to determine when it should be removed from service because of thinning in the bead areas Feeling the tube with the fingers will also reveal thinned areas On wheels with only one brake drum this heat set condition will normally show up only on one side of the tube In those cases where the brake drum is a considerable distance from the rim it is unlikely that this condition will ever be experienced Inspect For Wheel Damage e Wheels should be inspected following the wheel manufacturer s recommendations e In seneral make a visual inspection of the entire wheel Wheels that are cracked o
60. ive cage Use a bead breaker to loosen tire beads from both wheel half flanges e Always use proper bead breaking equipment designed for separa ting tires from wheel bead seats Do not use pry bars tire irons or any other sharp tools to loosen tire beads Damage to the tire and wheel may occur Do not loosen wheel tie bolts prior to breaking the beads loose Damage to the mating surfaces of the wheel halves can occur Ensure that the adaptor rings of the ring type bead breaker have passed over the wheel flanges and do not interfere with any wheel components rings Or press pads in contact with the tire are free of nicks burrs or sharp edges which could damage the tire surfaces e Apply bead breaker ram pressure Or arm pressure slowly or in a series of seguences or jogs to allow time for the tire s beads to slide on the wheel Because of the flexible side walls of a radial use of incor rect tooling or applying pres sure too rapidly can cause sidewall distortion Heavy dis tortion of the sidewall is not only harmful to the internal tire components but it may also begin to roll the beads making dismounting more dif ficult FIXED ADAPTOR RING e What To Do If The Tire Becomes Fixed To The Wheel If a tire bead rolls such that it will no longer slide on the wheel e Release ram pressure Apply a soap solution to the tire wheel interface Allow several minutes for the solution to pen
61. le aircraft or a fleet the principles and procedures contained in this manual will be of benefit If further information is needed please contact your Michelin Representative See back cover for regional contacts Tire Aircraft tire construction An 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 impact 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 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 bi
62. leak in the tire wheel assembly To avoid false readings tire pressure should be checked on cool tires air in a hot tire will expand causing a temporary higher pressure reading Wait at least 3 hours after landing or until the tire has reached ambient temperature as noted by carefully feeling with the palm the hand before making pressure checks If it is absolutely necessary to check pressures when tires are hot compare the relative pressures between tires on the same landing gear positions main or nose Never bleed pressure from a hot tire See Checking Hot Tires later in this section for details MICHELIN AIRCRAFT TIRE Effects of Underinflation Too little pressure can be harmful to your tires and dangerous to your aircraft and those in it Underinflated tires can creep or slip on the wheel under stress or when brakes are applied Valve stems can be damaged or sheared off and the tire tube or complete wheel assembly can be damaged or destroyed Excessive shoulder wear may also be seen Underinflation can allow the sidewalls of the tire to be crushed by the wheel s rim flanges under landing impact or upon striking the edge of the runway while maneuvering Tires may flex over the wheel flange with the possibility of damage to the bead and lower sidewall areas The result can be a bruise break or rupture of the cord body In any case where the bead or cord body of the tire is damaged the
63. liable service and avoids costly returns for repairs This basic pressure retention check reguires approximately 15 hours to determine if an assembly can be accepted for service Additional checks are performed on tire wheel assemblies not meeting the minimum acceptance criteria for pressure loss To follow this procedure reguires a pressure gauge 0 25 accuracy or better and capability to indicate 2 psi 15 bar pressure change Procedure Inflate the newly mounted tire wheel assembly to operating pressure for the aircraft application as specified in shop instruction manuals MICHELIN AIRCRAFT TIRE For safety use a suitable metal inflation cage when inflating tires Store the inflated tire wheel assembly for 3 hours El Check inflation pressure Be sure that the ambient temperature of the tire wheel assembly has not changed by more than 3 C 5 E Options f inflation pressure is equal to or greater than 2 9096 of the specified operating pressure proceed to Step 4 If inflation pressure is less than 90 of the specified opera ting pressure inspect the assembly for leakage Use a soap solution on tire beads and other susceptible wheel com ponents valves fuse plugs over pressurization plugs wheel half parting line etc If soap bubbles or leaks are found make appropriate repairs Return to Step 1 El Re inflate the tire to the speci fied operating pressure
64. nce mark heavy spot on the tube e Check for air trapped between the tire and tube e Use a soapy solution to check for leakage at the base of the tube valve stem where it exits the wheel Rolling the tire by taxiing will MICHELIN AIRCRAFT TIRE Certain aircraft have nose landing gears which are sensitive to vibration For these cases assemblies should be checked for balance and wheel weights added when required generally work any trapped air out from between the tube and tire els the tube wrinkled because of improper inflation procedures els the wheel out of balance because of improper assembly e Follow the wheel manufactu rer s instructions for properly aligning wheel halves e The balance mark on the tire should be aligned with the valve mounted on the wheel unless otherwise specified by the wheel manufacturer e Check the condition of the wheel to see if it has been bent e Check for a loose wheel bearing caused by an improperly torqued axle nut e Check for poor gear alignment as evidenced by uneven wear e Check for worn or loose landing gear components Ismounting MICHELIN AIRCRAFT TIRE AIRCRAFT TIRE EARLY REMOVAL TAG Data FIFE EARLY Cun FOD Belor Defonmed Low Pressure Cracking Vihirarinn Filet Tire nn Fuse Flug Male 1o Fliu LIT HER Tr Fai f HEET 2 Removal from landing gear It is further re
65. nd under the beads Within a few days as the tube expands to fill the void left by the trapped air the tire may become severely underinflated To compensate for this effect check tire pressure before each flight for several days after installation adjusting as necessary until the tire maintains proper pressure Inflation oressure maintenance Metric Units Temperature Rise 1 4 13 5 14 5 13 0 14 0 Temperature Drop 12 5 13 4 12 1 12 9 11 6 12 4 Units in C and Bars Effect of ambient temperature The above charts are a helpful gauge pressure example of the change in inflation pressure readings as a result of a change in ambient temperature For convenience it is given in metric units and in customary units Effect of Temperature Watch for severe changes in ambient temperature Changes in temperature affect gauge pressure readings as follows 1 change increase in inflation pressure reading for every 3 C 5 F change increase in temperature Customary Units Temperature Rise Temperature Drop F Proper Inflation Standard for Maintaining Pressure Level A cold tire is defined as a tire which has come to eguilibrium with its operating environment ambient temperature While the actual ambient temperature of the cold tire will vary from location to location and from season to season the operational inflation pressure PN as specified by
66. nge type Both designs facilitate the mounting and dismounting of the tire Show careful attention in handling assem bling and disassembling wheel com to avoid damage to critical surfaces 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 manujacturers 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 MICHELIN AIRCRAFT TIRE 27 Wheel half and O Ring Direct particular attention to the following e Ensure that the bead seating area of the wheel is clean and uncontaminated e Mating surfaces of the wheel halves should be free of nicks burrs small dents or other damage that could prevent the surfaces from properly mating or sealing Painted or coated surfaces should be in good condition not badly chafed chipped etc e Be sure fuse plugs inflation valves and wheel plugs are in good condition properly sealed against loss of pressure and correctly torqued per the manufacturers instructions e O Ring grooves in the wheel halves should be checked for damage or other debris that would prevent the 0 Ring
67. not needing lower sidewall vents will have no color dot in this zone General mounting instructions for aircraft tires Storage of an inflated tire and wheel assembly Once a tire has been properly mounted and the assembly verified for pressure retention only minimal precautions need be taken e Do not expose the tire to excessively high temperatures greater than 40 104 e Do not expose the tire to direct sunlight or to high ozone concentrations e Avoid contact with contaminants oil grease etc Mounted tire wheel assembly properly prepared and delivered to a line mainte nance station as an airworthy replacement unit should meet the following storage conditions e The pressure level should be set at operational pressure for the tire application Do not exceed operational pressure Note It is acceptable to STORE the mounted assembly pressurized in this range for up to 12 months After 12 months any inflated assembly which has not been introduced into service should be returned to the wheel mounting shop The following inspections and actions should be taken with the assembly before returning it to service This storage and re inspection interval can be repeated multiple times so long as the tire meets all criteria However to maximize tire life it is recommended to rotate replacement stock The conditions of storage and the tire s response to those conditions will determine
68. nts etc can damage aircraft tires by softening or deteriorating the rubber surface During aircraft maintenance tires should be covered to protect them from accidental spills Keep runway surfaces clean so that tires are not parked in surface puddles Immediately upon contact with a hydrocarbon substance wash the contaminated area first with denatured alcohol then with a soap and water solution If the rubber feels soft or spongy when probed remove the tire from service Nylon Flat Spotting Nylon aircraft tires will develop flat spots under static load The degree of this flat spotting will vary according to e the temperature of the tire when the aircraft is first parked e the pressure in the tire the load being applied to the tire while the aircraft is parked e the ambient temperature e the length of time the tire is subject to a combination of the above conditions the type of construction under similar conditions a radial tire will develop less flat spotting than will a bias tire On a practical level aircraft maintenance personnel cannot influence all of these variables minimize the condition inflation pressures should be kept at their specified operating levels and loads held to a minimum during the static load period Under normal conditions a flat spot will disappear by the end of the taxi run In the unusual case where deep flat spotting has occurred additional taxiing is re
69. ounted 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 causes of pressure loss in a tire growth during the first 12 hours after mounting and inflation to the specified operating pressure This is entirely normal e To avoid a possible underinflation condition it is important that a tire not be placed in service until it has undergone the complete growth cycle and has been reinflated to the specified operating pressure An apparent pressure loss can be caused by drop in ambient temperature Was the tire inflated in a heated room and stored in an unheated one Was the tire relocated from a warm climate to a cold climate For more details on the effects of ambient temperature see page 42 Use only an approved calibrated gauge preferably of a dial or digital type It is best to use the same gauge when monitoring a slow pressure loss in a tire wheel assembly eForeign object damage that penetrates the cord body and liner Inspect the tire carefully for any FODS e Check for improperly seated beads This condition can be identified by comparing the position of the tires lower sidewall annular rings mold lines or branding Look to see if they are uniform from side to side or that they are ab
70. ove 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 e Leaks at the valve stem or valve core Put a small amount of water on the end of the valve stem and watch for bubbles If bubbles appear replace the core and repeat the check Valve caps finger tightened should be used to prevent dirt from entering and holding open the valve stem e 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 wheel manufacturer must be used e Wheel half parting line O ring seal tubeless tires leaks in service e Twisting or failure to lubricate the O ring before installation may cause leakage at the wheel mating surfaces Use of the wrong O Ring com pound as specified by the wheel manufacturer suitable for the intended aircraft service in particular low temperature service may also cause leakage at the wheel mating surfaces e This type of leakage is very dif ficult to diagnose since the in service conditions causing the leakage are not reproducible in a shop e Leakage through the fuse plug tubeless tires Use sealing gaskets specified by the wheel manufac
71. priate wrapping such as dark polyethylene paper Mounted Tire Mounted tires not immediately placed in service should be covered wrapped until they are to be installed on an aircraft 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 L mounting EZ e T 1 1 ERE a E i m c m m A eo l 1 L 1 LT 9 L 2 ON Li NN al mounting instructions for aircraft tires E EI 7 M Gene r 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 eguipment 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 fla
72. pting Tires For Retreading 78 Repairing Aircraft Tires 78 Non Repairable Aircraft Tires 79 Repairable Aircraft Tires 79 Operating and Handling Tips for Better Tire Service 80 Taxiing 81 Pivoting By Using Brakes 81 Condition of Airport Field 82 Avoid Chemical Contamination 82 Nylon Flat Spotting 82 Chevron Cutting 83 Hydroplaning 83 Landings Per Tread 84 For aircraft tires to deliver maximum performance reliability durability and safety they must be properly cared for and serviced This manual is designed as a guide to the procedures to be used for all aspects of aircraft tire care and operation It provides detailed information about how to operate aircraft tires to achieve optimum service It also covers installation removal and servicing techniques It should be used in conjunction with the operating procedures given by the aircraft and wheel manufacturers The procedures given in this manual apply to all Michelin manufactured 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 same service and care techniques should be used for both Bias and Radial tires In some specific cases due to the nature of bias and radial tire constructions differences in service techniques may exist Where applicable these differences have been noted Whether you operate a sing
73. r damaged should be immediately taken out of service for further checking repair or replacement e If used check the condition of the thermal fuse plug or overinflation plug Melted pushed out or leaking plugs should be replaced Be sure that sealing gaskets are the ones specified by the wheel manufacturer for the service conditions of the aircraft Gaskets should be free from distortion and damage If a fuse plug blows while the tire is rolling the tire and its axlemate should be scrapped because both tire will have been subjected to overload conditions Matching Mieability Matching and d mixabi ity of dual tires i Matching Tires In applications involving dual wheels or dual wheels on a multi wheel landing gear configuration tires should be matched in diameter or static loaded radius within the appropriate association s T amp RA ETRTO MIL T 5041 AIR 8505A etc inflated dimensions for both new and grown tires It is important to ensure equal distribution of aircraft load on all tires and to avoid over loading a tire beyond its limits Matching Criteria Matching tires assures that the sizing of the tires is such that both tires will carry within industry standards equal loads e Bias tires e Same Size e Same Type e Within the Overall Diameter limits as recommended by the governing association for the particular application civil military
74. raft speed remains below normal landing speeds and normal braking energies are experienced tires may be left in service A visual inspec tion should be made on each tire to assure all tires meet the serviceability criteria Pay par ticular attention to any tire flat spotting that may have occur red as a result of braking A minimum 30 minute tire brake cooling period is requi red prior to the continuation of the aircraft s flight schedule MICHELIN AIRCRAFT TIRE e Where aircraft speeds exceed normal landing speeds and high braking energies are experienced tires should be removed from service labeled as an RTO tire and returned to the retreader for inspection and disposition Off Aircraft Inspection With Tire Dismounted A Systematic Approach to Tire Inspection A systematic approach to tire inspection is recommended to insure that all areas are properly inspected The following system is recommended Inspect the Tread Area Follow the procedures given for On Aircraft Inspections After the tread area Inspect Both Sidewall Areas Follow the procedures given for On Aircraft Inspections Inspect the Bead Areas e Check the entire bead area from just above the heel of the bead to innerliner for chafing from the wheel flange or damage from tire tools Tire serviceability criteria e For Bias Tires e An exposed chafer strip on the bead face will normally cause no trouble
75. ring tire growth is considered normal More than that may indicate a lea kage problem Be sure that the tire assembly has remained at a cons tant ambient temperature 3 C 5 F A drop of 3 C 5 F will reduce inflation pressure 196 Check for Leakage After growth period reinflate the tire to the specified operating pressure Recheck the pressure after 24 hour period A pressure loss of 5 or less is considered normal Be sure that the ambient temperature of the tire has not changed by more than 3 C 5 E If a greater than 5 pressure loss occurs investigate the tire wheel assembly for leaks Do not put the tire into service until the leak source is identified and corrected If the pressure loss is within the acceptable 5 limit the assem bly is now ready to be installed on the aircraft Note that once in service the tire wheel assembly maximum daily 24 hours pressure loss is 5 Typical rates are 0 2 2 0 per 24 hour period Sidewall venting Aircraft tires have traditionally been designed to permit any air or nitrogen trapped in the cord body or that diffuses through the liner or tube to Sidewall vent holes escape through special sidewall vents Tires reguiring vent holes have them placed in the lower sidewall This venting prevents pressure build up within the carcass body which might cause tread sidewall or ply separations The location of each vent hole on the new tire is indicated by a color
76. s Manual must be followed Checking Duals for Egual Operating Pressure Tires mounted as duals or on the same bogey whether main or nose whether bias or radial should be maintained at egual operating pressure If pressures are not egual the tire with the highest pressure will be carrying an unegual proportion of the load even though there may be no perceptible difference between tire deflections The graph on page 41 demonstrates this concept If it is determined that dual mounted tires are operating at unequal pressures more than 5 is cause for special attention inflate both tires to their proper pressure Make a logbook entry indicating the original pressure differential the date and time corrected and the ambient temperature At each subsequent pressure check the logbook should be consulted Effects of Unegual Tire Pressure on Loads If the same tire continues to evidence a pressure loss it should be checked for leakage FOD valve core etc If no obvious cause is found the tire should be removed and given a thorough inspection until the reason for the pressure loss can be determined For mixability of bias and radial tires see the section on Matching Dual Tires in this manual Proper Inflation Setting the Pressure Level Inflating and Reinflating the Tire Wheel Assembly Whether for tubeless or tubetype tire operating pressures should be set following the instructions given b
77. s with injuries or damages can be repaired at the time of retreading and put back into useful safe service Injuries must be within the manufacturers repairable limits Tires with sidewall cuts snags scuffs and cracking from ozone can remain in service if the carcass ply is not exposed Damages that expose carcass textile can be repaired by an approved repair station if the cords are not cut or damaged Note Repairable limits generally exceed service ability limits used to remove tires from ser vice Detailed safe inspections suitable for determining the gravity of an injury cannot be made on inflated mounted tires Service removal limits are further set to ensure safe operation and retreadability of the casing Non repairable aircraft tires The following list outlines some of the conditions which can disqualify a tire from being retreaded e Any injuries to the beads or in the bead area except injuries limited to the bead cover or finishing strip e Weather checking or ozone cracking of tread orsidewall that results in exposed body cords e Protruding bead wire or kinked bead e Ply separation e Internal damage or broken cords e Flat spots and skid burns that have penetrated to the top carcass ply Wearing the tire beyond the protector ply or reinforcing plies can leave insufficient interface rubber to allow retreading Punctures that penetrate the innerliner Excessive brake heat damage such
78. sed to reinforce the carcass in the tread area of the tire ORIONTM technology ORIONTM technology is a development unigue to Michelin Bias construction It consists of a CROWN REINFORCEMENT placed on the inside of the tire This CROWN REINFORCEMENT strengthens and provides a more uniform pressure distribution in the footprint SLOWING THE RATE OF WEAR improving landings performance in a lighter tire design tread sidewall tread reinforcing ply undertread carcass plies i A AO AN liner carcass ply turn ups beads Ichafer strips Bias Tire Construction Fabric tread not shown is a unigue development for application on high speed military aircraft Multiple plies of nylon cord are layered throughout the tread stock reducing rubber distortion under load and high speeds thus reducing heat normally generated by flexing The laminates also control the formation of high speed standing waves Improved resistance to cuts and punctures is also a benefit of this type of construction Spiral Wrap not shown is a technigue used with retreaded tires Individual textile cords are layed within the replacement tread rubber as 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 circumferential orientation the textile cords provid
79. sidewall of the tire It is important that the adaptor rings be designed for the particular tire wheel assembly to be dismounted The optimum condition is an adapter ring internal diameter as close to the wheel flange diameter as possible Pushing too high on the tire sidewall will General dismounting instructions for aircraft tires only distort the sidewall and bead area making dismounting more difficult For practical purposes a radial clearance between the tip of the wheel flange and the internal diameter of the adaptor ring is necessary to avoid interference between the wheel and adaptor ring as it approaches and travels over the wheel flange Michelin recommends a radial clearance of 0 4 inches 10 mm The movement travel of the adaptor ring should be at least four 4 inches 100 mm to ensure complete separation of the tire from the wheel It is desirable that the rings be designed such that the tire can be observed while pressure is being applied to ensure satisfactory ring contact and progress PRESS ARMS Pincher type bead breaker e Localized pincher type bead breaker This equipment consists of two press arms which can be operated in a pincher movement At the end of each arm is a press pad in the form of a sector An adjustable cylinder is used to position the tire so that the sectors can be matched to the size of the tire The tire wheel assembly is positioned s
80. t action for obtaining optimum tire performance is a program of regular tire inflation maintenance user pilot actions and the condition of the airport surfaces are also important The following information is to help bring an awareness of these important factors which can further your tire investment Taxiing Unnecessary tire damage and excessive wear can be prevented by proper handling of the aircraft during taxiing Most of the gross weight of any aircraft is borne by the main landing gear which may consist of two four eight or more tires The tires are designed and inflated to absorb the shock of landing and will normally deflect about three times more than a passenger car truck tire The greater deflection allows tire to carry the heavy loads It also causes more working of the tread produces a scuffing action along the outer edges of the tread and results in more rapid wear If an aircraft tire strikes a chuckhole stone or some foreign object lying on the runway taxi strip or ramp there is more possibility of it being cut snagged or bruised because of the high operational deflection If one of the main landing gear wheels when making a turn drops off the edge of the paved surface this may result in severe sidewall or shoulder damage The same type of damage may also occur when the tire rolls back up over the edge of the pavement With dual main landing gear wheels it is important that t
81. ter Store tubes properly Michelin tubes should always be stored in their original cartons so they are protected from light and air currents If stored without their cartons they should be wrapped in several 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 size tire This of course should only be done as a temporary measure Before mounting a tire and tube stored in such a manner always remove the tube from the tire and inspect the inside of the tire for foreign material which if not cleaned out could cause irreparable damage to both tube and tire Under no circumstances should tubes ever be hung over nails or pegs or over any other object which might form a crease in the tube Such a crease will eventually produce a crack in the rubber and cause tube failure Tire or tube age limit Michelin aircraft tires or tubes have no age limit and may be placed in service regardless of their age provided all inspection criteria for service storage mounting and individual customer imposed restrictions are met MICHELIN AIRCRAFT TIRE Note Certain regulatory agencies recommend further restricting the age of rubber products used in the aircraft industry The decision to adopt these recommendations must be made by the individual user Storage of inflated tire and wheel assemblies Mounted tire wheel assembly properly prepared and
82. tor s Manual for the particular aircraft MICHELIN AIRCRAFT TIRE Important Check pressure with aircraft load on tire Use loaded operating inflation pressure Operational pressure values are for loaded tires e Loaded inflation pressure 104 unloaded inflation pressure pressure Inflation 0 pressure maintenance Proper inflation getting the most out of your tires The most important service you can perform on your aircraft s 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 It is the Key to Optimum Service If you make one or more flights a day tire pressure should be checked daily with an accurate calibrated gauge preferably with a dial digital indicator appropriate for the pressure range of your tires When installed the TPIS Tire Pressure Indicator System can be used to make the daily inflation pressure check provided the TPIS indicators are verified against a calibrated pressure gauge at each aircraft check If you fly less than one time per day you should check tire pressure before each flight Be particularly alert to severe temperature drops which will also reduce tire pressure Repeated pressure losses beyond the daily 5 under constant temperature conditions may signal a slow
83. trical devices since they all create ozone Store away from fuel and solvents Make sure that tires do not come into contact with oil gasoline jet fuel hydraulic fluids or other hydrocarbon solvents since all of these are natural enemies of rubber and cause it to disintegrate rapidly Be especially careful not to stand or lay tires on floors that are covered with oil or grease When working on engines or landing gears tires should be covered so that oil does not drip on them pe s tubes 1 Protect tires from contaminants If tires accidentally become contaminated wash them off with denatured alcohol and then with a soap and water solution After cleaning be sure to remove any water that may have accumulated in the interior of an unmounted tire If after cleaning the surface of the tire appears soft spongy or bulges are present the tire is not suitable for service Should you have any doubt about the serviceability of such a tire please contact your Michelin Representative or authorized repair station Store in the dark The storage room should be dark or at least free from direct sunlight Windows should be darkened with a coat of blue paint or covered with black plastic Either of these will provide some diffused lighting during the daytime Black plastic is preferred since it will lower the temperature in the room during the warm months and permit tires to be stor
84. turer suitable for the intended aircraft service in particular for low temperature service A faulty fuse plug can allow a seepage of nitrogen and thus a loss of pressure ePressure release plug tubeless tires Some wheel designs have a pressure release plug The potential causes of leakage are the same as for a fuse plug MICHELIN AIRCRAFT TIRE eSeepage between tire bead and wheel flange tubeless tires can occur An inspection should be made with particular attention to the following Look for exposure of cord body in the bead toe area or bead flat area Exposed cords may act as a wick for nitrogen to escape along Foreign material trapped bet ween the bead and wheel sea ling surfaces causing a poor sealing between the tire and wheel Gouges or scratches resulting from handling or improper use of tire irons Damage can also occur along the wheel half mating surfaces and leakage may show in the O ring seal area Corrosion or wear in the bead ledge area usually toe area of the tire bead will leak at the tire wheel contact area Inflation oressure maintenance Initial Stretch Period 24 Hour Tire Growth Changes In Air Temperature Venting of Tubeless Tires Release of Trapped Air in Tube Type Tires Cut or Puncture Damaged Beads Improperly Seated Beads Leaking Valve core Other Valve Problems Improper Installation of O Rings Faulty Thermal Fuse or Installation Porous W
85. uch that the press pads contact the tire s lower sidewall just above the wheel flange Pressure is applied to break the beads After the first sector of the tire begins to move away from the wheel flange stop rotate the tire wheel assembly a short distance and repeat the operation until all sectors of the tire are loose and free from the wheel Note When pressing against the tire hold the pressure for 1 2 seconds to allow the bead time to move Bead breaking is most efficient when the tire wheel assembly is rotated approximately 30 degrees bet ween each pressing operation The press pads used to push the tire are universal and are designed to push on the tire close to the wheel flange No specific tooling is required for the different tire sizes to be handled Repair TE UTE gt aircraft tires Many aircraft tires that become injured in service can be successfully repaired Tires of which the treads are worn out flat spotted or otherwise damaged but of which the cord body is intact can be retreaded Retreading and repairing aircraft tires has been a common practice for many years and can save aircraft operators considerable sums of money Tires that might otherwise have been discarded due to insufficient or damaged tread can be retreaded or repaired for continued service at a cost much lower than that of a new tire Retreading and repairing
86. ure trouble free dismounting Recommended information includes Name of Operator Date of dismounting e Aircraft model tail number Tire part number Tire serial number Reason for removal Number of tire landings General dismounting instructions for aircraft tires Bead roll over Tire Wheel Dismounting e Completely deflate the tire e Ensure the faces of the adaptor Sequence The same methods are essentially used for dismounting tubeless bias tube type bias and radial aircraft tires However radial tires have a smaller bead flat area and have a more flexible sidewall which requires that more attention be placed on the tooling set up Failure to use proper tooling designed for the particular tire size could result in dismounting difficulties Follow the tooling guidelines given in the next section Once tooling has been set up dismounting should occur in a similar manner for both bias and radial tires tubeless and tube type Before beginning any tire dismount be sure to follow the instructions and precautions published in the wheel suppliers maintenance manual Mark damaged or bulge areas before deflating using a contrasting color chalk or tube before dismounting e Use caution when unscrewing valve cores The pressure within the tire or tube can cause a valve core to be ejected at high speed If damage has occurred tire wheel assembly should be deflated in a protect
87. ures for initial inflation and adjustments must comply with applicable instructions as given in FAR 25 or JAR 25 Oxygen concentration should never exceed 5 Basic Pressure Retention Procedure Special Procedure To Properly Seat Tube Type Tires To seat tire beads properly on the wheel e Inflate the tire to the recommen ded pressure for the aircraft on which it is to be mounted Next completely deflate the tire Finally reinflate it to the correct pressure do not fasten the valve to the rim until this has been done Use a valve extension for inflation purposes if necessary This procedure helps remove any wrinkles in the tube and helps prevent pinching the tube under the toe of the bead It eliminates the possibility of one section of the tube stretching more than the rest and thinning out in that area Further it assists in the removal of air that might be trapped between the inner tube and the tire Note With tubeless tires this inflation deflation reinflation procedure is not necessary Tire Wheel Assembly 3 hours If lt 9096 If gt 90 12 hours If lt 97 5 24 hours If gt 97 5 If lt 97 5 Basic pressure retention check Pressure retention checks are designed to verify that tire wheel assemblies meet industry standards for pressure retention prior to releasing them for service on aircraft This important process assures re
88. ven for checking the pressure of a hot tire the following instructions and precautions should be followed Continued from page 44 94 90 Accidental Pressure Loss 89 80 Pressure Loss 79 0 Major Pressure Loss Pressures measured from tires on the same landing gear should be of the same magni tude They should always be at least egual to the specified operating 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 to an authorized repair facility for examination Aircraft flying between airports with a significant temperature drop should be aware of the effects of temperature on inflation pressure See section Effects of Temperature Do Not Reduce The Pressure of a Hot Tire The basic rules to follow for correcting inflation pressure hot tires on the same landing gear Should always be at least egual to and may exceed the specified operating pressure r If one tire is approximately egual in temperature but low in pressure it should be brought up to the pressure level of the other tire In all cases both tires should be at least egual to or greater than the specified operating pressure Check all tires on the gear Any tire that is approximately egual in temperature but low in pressure should have its inflation increased such that all tires are within a 5 pressure ran
89. y body for the airline Transportation of a serviceable inflated aircraft tire is covered by the U S Department of Transportation Code of Federal Regulations the International Air Transport Association IATA and other regulatory bodies While serviceable tires may be shipped fully pressurized in the cargo area of an aircraft Michelin s recommendation is to reduce pressure to 25 of operating pressure or 3 bars 40 psi whichever is the lesser Reinflate to operating pressure before mounting on the aircraft MICHELIN AIRCRAFT TIRE m ing on aircraft 5 Mounting tirejwheel E assembly on the aircraft Visually Inspect Tire Wheel Assembly Visually Inspect Tire Wheel Assembly for damage from handling storage or contaminants Look for deformations bulges swelling blisters or other anomalies that would make the assembly unserviceable e Superficial cuts cracks not reaching the cord body are acceptable for service e Groove cracking that does not reach the protector or reinforcing ply is acceptable for service Follow the guidelines given in this Manual for serviceability Readjust Tire Pressure Readjust Tire Pressure after mounting the tire wheel assembly on the aircraft Operating pressures are set by the airframe manufacturers based on a variety of factors including maximum ramp or taxi weight center of gravity and dynamic loading Reference the Opera
90. y the airframe manufacturer For newly mounted tires follow the instructions given in the section on General Mounting Instructions For Aircraft Tires Dual Tire Axle When required reinflate tires to their specified operating pressure with a dry commercial grade nitrogen of at least 97 purity In some Cases nitrogen may not be available for adjusting tire inflation When this occurs clean dry air may be used as long as the oxygen content does not exceed 5 of the total tire volume If the 5 oxygen limit is exceeded the tire must be deflated and then reinflated with nitrogen 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 MICHELIN AIRCRAFT TIRE Loaded versus Unloaded Tires Be sure that it is clear whether operating inflation pressures are given for loaded or unloaded tire conditions A tire s 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 the tire and the tube at the time of mounting Although initial readings indicate proper pressure the trapped air will seep out around the valve stem hole in the wheel a

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