5-2Wheels and Tyres

AMS 5 Part 2

AMS 5.2

Describe the construction of aircraft tyres, identify them by their markings and state their application.

AMS 5.3

Describe the precautions to be observed during inflation of aircraft tyres.

AMS 5.4

Identify faults and damage that render tyres unserviceable.

AMS 5.5

Describe the types of wheels used on aircraft and state their applications.

AMS 5 - 2Wheels and Tyres

Provide a cushion of air that helps absorb the shocks and roughness of landings and takeoffs.

Support the weight of the aircraft while on the ground

Provide the necessary traction for braking and stopping aircraft on landing.

Aircraft tyres must be carefully maintained

to meet the rigorous demands of their basic job;

to accept a variety of static and dynamic stresses dependably in a wide range of operating conditions.

Tyres

The basic parts of a tyre consist of the:

Bead,

Carcass,

Tread and

Sidewall.

Tyre Construction

Tyre Construction

Plain tread All-weather tread

Tyre Treads

Rib tread

Deflector

Manufactured in a variety of sizes and strengths,

Correct types are specified by the manufacturers,

according to the size and landing speed of the aircraft

involved. Construction is similar to motor vehicle

and truck tyres. The number of fabric plies in the tyres

varies from 2 to 16 or more.

Classification of Aircraft Tyres

The majority of tyres in use today on light aircraft

are of the tube-type, make use of inner tubes to

hold the air charge most transport aircraft tyres are of the

tubeless type. Balance marks are placed on tyres in

the form of a red dot on the side of the tyre at the lightest point.


Classified by type numbers according to performanceTyre Type Design and Rating

I Smooth contour

II High pressure

III Low pressure

IV Extra low pressure

V Not applicable

VI Low profile

VII Extra high pressure, low speedExtra high pressure, high speed

VIII Extra high pressure, low profile, low speedExtra high pressure, low profile, high speed


Classified by type numbers according to performance

Tyre Type Design and Rating

V Not applicable



Tyres classified as Types I, II, IV, and VI are phasing out because these classifications are inactive for new designs.

Smooth contourI

High pressureII

Extra low pressure

Low profileVI

IIILow pressure

IV


Classified by type numbers according to performanceClassification of Aircraft Tyres

Design and RatingTyre Type

III Low pressure

V Not applicable



Tyres classified as Types III, VII, and VIII are manufactured under the provisions of FAR 37.167 and are approved under Technical Standard Order (TSO) No. C62b.

Such tyres are required to be permanently marked with: the brand name or name of the manufacturer

responsible for compliance and the country of manufacture if manufactured outside

the United States; the size, ply rating, and serial number; the qualification test speed and skid depth when the

test speed is greater than 160 mph (257.6 km/h), the word reinforced if applicable; and the applicable TSO number. Type III tyres and those specified as low-speed tyres are

approved for ground speeds of less than 160 mph (237.6 km/h).

In all cases of tyre replacement, the aircraft technician must determine that the type of tyre specified for the aircraft is installed.


Type I Smooth Contour

This tyre is in use today but is considered obsolete and is not used on new design aircraft.

Typical size: 14.50" (outside diameter).

Tyre Types

Type II High Pressure

Type II tyres were brought out with the introduction of the retractable gear as a more compact replacement for Type I. Type II have been replaced largely by Type VII tyres which have higher load capacities.

Typical size: 26 x 6 = (outside diameter) x (section width).

Tyre Types

Tyre III Low Pressure

The Type III tyre is used on most piston driven aircraft today.

The section width is relatively wider in relation to the bead diameter.

This provides lower pressures for improved cushioning and flotation. Goodyear makes many sizes of Type III tyres (in both tubeless and tube type) for tail, nose and main wheels.

Typical size: 9.50‑16 = (section width) ‑ (rim diameter).

Tyre Types

Type IV Extra Low Pressure

This type of tyre came in with the need for more flotation and cushioning than was provided by Type III tyres.

They have a very large section width in relation to the bead diameter.

Made in limited quantities, Type IV tyres are almost obsolete.

Sizes made are all tube type construction for tail and main wheels.

Typical size: 35 x 15-6 =

(outside diameter) x (section width) ‑ (rim diameter).

Tyre Types

Type VI Low Profile

Made especially for nose wheels,

Type VI tyres are noted for their low sectional height (low profile).

This minimises wheel drop in the event of a flat tyre.

Typical size: 15 x 6.00‑6 =

(outside diameter) x (section width) ‑ (rim diameter).

Tyre Types

Used almost universally on today's jet aircraft.

Type VII tyres are characterised by their conventional shape and very high load capacities.

Goodyear currently produces many sizes of Type VII tyres with ply ratings ranging from 4 to 38, used on nose and main wheels.

Type VII Extra High Pressure

Typical size: 39 x 13 = (outside diameter) x (section width).

Tyre Types

Type VIII Extra High Pressure Low Profile, High Speed

Type VIII tyres are used for high performance jet aircraft with their extremely high takeoff speeds.

They use extra high inflation pressure and have a low profile.

Their size designation includes the outside diameter, section width, and rim diameter.

An example of a tyre designation for a Type VIII tyre would be 30 x11.50‑14.5

Tyre Types

Heat is generated within the tyre as it rolls over the ground, or from external sources such as the brakes or hot runway surfaces.

Internally generated heat causes damage. Sidewalls flex and cause internal heat,

Designed to withstand the heat generated by this normal flexing for a reasonable amount of time.

Air in the tyre supports the weight of the aircraft,

Inflation pressure is critical.

Should be checked daily and before each flight.

Tyre Inspection on the Aircraft

Over-inflation causes accelerated centreline wear on the tread while leaving rubber on the shoulder.

Much less resistance to skidding than it has when its tread wears uniformly.

While over-inflation is bad, under-inflation is even worse,

Causes excess heat to be generated within the tyre.

If a tyre is allowed to deflect as much as 45%, about three times as much heat will build up in the tyre as it is designed to withstand.

This over-deflection can cause internal carcass damage, which may not be visible and could easily result in premature failure of the tyre.


Tyres that have been operated with low inflation pressure will have their tread worn away on the shoulders more than in the centre,

Any tyre showing this pattern of wear should be carefully examined for evidence of hidden damage.

Maintaining the proper inflation pressure in a tyre makes pressure checks one of the most important parts of routine preventive maintenance.

The proper inflation pressure is that specified by the airframe manufacturer in their service manuals,

For the same tyre, varies from one aircraft design to another.

This pressure should be used, rather than that listed in the tyre manufacturer's product manuals.


The pressure specified in the airframe manufacturer's manual is for a loaded tyre;

for the tyre supporting the weight of the aircraft.

When the tyre is subjected to this load, it will be deflected the designed amount, and

The volume of its air chamber will be decreased enough to raise the pressure by about four percent.

If the service manual specifies a pressure of 187 psi, the proper inflation pressure when the tyre is not supporting the aircraft is 180 psi.


Inaccurate pressure gauges are one of the major causes for chronic inflation problems.

To be sure that the gauge is accurate, have it periodically calibrated so it can be relied on.

The best gauges for this purpose are dial-type indicators, since they are less subject to careless handling and are easier to read in the small increments needed to accurately determine the tyre pressure.


Inflation pressure should always be measured when the tyre is cold

Allow two to three hours to elapse after a flight before you measure the pressure.

Inflation pressure of a tyre varies with the ambient temperature by about one percent for every five degrees Fahrenheit.

Example, if a tyre is inflated and allowed to stabilise with a pressure of 180 psi in a shop where the temperature is 70F, and the aircraft is rolled outside where it remains overnight with a temperature of zero degrees F.

The pressure will drop by 14% to about 155 psi.

It will be under-inflated and should be re-inflated.


If an aircraft is to fly into an area where the temperature is much lower than that of the departing point, theoretically, the pressure should be adjusted before the aircraft leaves.

If, the temperature is 100 F and the aircraft is to land where the temperature is 40 F, the pressure should be increased before takeoff.

If the tyre requires 187 psi, the 60 degree temperature drop will require the pressure to 12% greater, or 210 psi.

The airframe manufacturer's manual should be consulted before the pressure is changed to see if the maximum allowable safe inflation pressure has not been exceeded.

Nylon tyres will stretch when they are first inflated and will increase their volume enough to cause a pressure drop of about five to ten percent of the initial pressure in the first 24 hours.

Their pressure should be, adjusted 12 to 24 hours after installation.


The basic strength of the tyre is in its carcass.

Tyre loses none of its strength as long as the tread does not wear down into the body plies of the carcass.

When the tread is worn away, the traction characteristics of the tyre are seriously affected.

A tyre that has been properly maintained and operated with the correct inflation pressure will wear the tread uniformly,

Should be removed for retreading while there is still at least 1/32‑inch of tread left at its most shallow point.

When the tyre is removed at this point, there is still enough tread left to provide traction and handling during wet runway operation

Normal Inflation

Tread Condition

Over inflated Tread wear

Over-inflated

Centre ribs are worn away while the shoulder ribs still have an appreciable depth,

The tyre has been operated in an over inflated condition,

Highly susceptible to cuts and bruises.

Should be carefully checked for this type of damage.

Tread Condition

Under-inflation

Under-inflation

will cause the shoulder ribs to wear more than those in the centre.

Any tyre showing this wear pattern should be carefully inspected for signs of bulges, which could indicate ply separation.

Tread Condition

Poor maintenance

Tread that has been worn until the body plies are visible indicates poor maintenance.

If it is worn only to the point that the tread reinforcement is showing, it is possible that retreading can salvage the tyre.

If it is worn into the body plies, it has gone too far to be saved.

Tread Condition

Tread Condition

Tread cut more than halfway across a rib, or any of the carcass plies are exposed, the tyre should be removed.

Bits of glass, rock, or metal embedded in the tread, they should be carefully pried out with a blunt awl or a small screwdriver.

Cuts in Tread

Tread Condition

When a wheel locks up on a water covered runway and rides on the surface of the water, a tremendous amount of heat builds up at the point of contact and actually burns the rubber.

Tyres showing heat/burn damage should be removed from service.

AquaplaneDamage

Tread Condition

Operating on grooved runways can cause chevron-shaped cuts across the ribs of a tyre

If cuts extend across more than one-half of the rib, the tyre should be removed from service.

Mark any damage or suspect area of the tyre with a light coloured crayon before deflating the tyre, because when the air is out, these areas will be almost impossible to locate.

Grooved RunwayDamage

Tread Condition

Jack the aircraft according IAW the aircraft service manual,

When the weight is off of the tyre, deflate it using a deflator cap.

The high pressure in some aircraft tyres can eject the valve core with enough velocity to injure anyone it might hit,

After all of the air is out, the core may be safely removed.

Remove the wheel, following the aircraft manufacturer’s instructions in detail.

Ensure that the bearings are protected from damage and are stored in a safe place until they can be cleaned, inspected, and repacked with proper grease.

Tyre Removal

Place the wheel on a flat surface and break the bead away from the wheel, using a straight push as near the rim as possible.

Never use any kind of tyre tool to pry the bead from the wheel,

The soft metal of which the wheel is made can be easily nicked or scratched,

This type of damage will cause stress concentrations that will lead to wheel failure.

When the bead has been broken from both sides of the wheel,

Remove the wheel bolts and lift the wheel half from the tyre and remove the tyre.

If the tyre is tubeless, be careful that the O-ring seal between the wheel halves is not damaged.

Tyre Removal

Any tyre that has been involved in an aborted takeoff or severe braking should be replaced

Any tyre that has been exposed to enough heat that the fusible plug in the wheel has blown and deflated the tyre, should be replaced.

This excessive heat has caused damage to the tyre that has weakened the tyre enough that it will likely fail in service.

If one tyre in a dual installation fails, there have been enough extra stresses put into the other tyre that it should be discarded too.

Tyre Inspection Off The Aircraft


Carefully spread the beads apart so the inner liner can be inspected.

Don't concentrate the force used to spread the beads, and don't spread them more than the section width of the tyre.

The use of improper procedure when breading the bead or when spreading it can kink the wire bundles so the bead cannot seat against the wheel when it is reinstalled,

A tyre with a kinked bead should be scrapped.


Carefully examine the inner liner of tubeless tyres for any bulges or blisters, and have any suspect areas evaluated by a retreading agency.

Probe all of the suspected areas that were marked when the tyre was inflated.

When checking any cuts, open them up enough that you can see into their depth, but be sure you don't puncture the tyre.

Punctures that do not exceed a quarter inch on the outside of the tyre and one-eighth inch on the inside and injuries that do not, penetrate more than 40% of the actual body plies can be repaired when the tyre is retreaded.

Tyre Inspection Off The Aircraft If any bulges were marked when the tyre was

inflated, carefully check them to determine whether they are ply separations or separations between the tread and the carcass.

If it is a ply separation, the tyre must be scrapped, but tread separation may possibly be repaired by retreading

Carefully examine the sidewall for condition.

If any of the cords have been damaged or exposed, the tyre cannot be repaired.

It is reasonable to suspect that the exposed cords have been weakened by exposure to the elements.

Tyre Inspection Off The Aircraft The most important part of a tyre is the bead area

where all of the forces of the tyre are carried into the wheel and where an air-tight seal must be maintained with tubeless tyres.

Carefully examine all of the bead and the adjacent area for indication of damage from tyre tools or from chafing against the rim.

Any severe damage here would require the tyre to be scrapped, but if the damage is only through the chafer, it can be repaired when the tyre is retreaded.

Tyre Inspection Off The Aircraft Damage from excessive heat will usually show up on

the bead area. Heat can build up here faster than it can be

dissipated. If any of the bead area is damaged or has an unusual

appearance or texture. The tyre cannot be repaired.

The bead surface from the wheel flange to the toe of the bead is the sealing surface for a tubeless tyre, and

if it has been damaged by tyre tools or by slipping on the wheel, it will not seal.

Bare chafer cords, however, if they are not broken, will not normally cause a tyre to leak.

they are not necessarily a cause for removing the tyre from service.

Aircraft tyres are highly stressed, and no repair should be attempted by anyone not adequately equipped for or experienced in this work.

General guidelines for repairable tyres are given in the FAA Advisory Circular 43,13‑1A in the USA.

Actual repair should only be made by a repair station equipped and approved for this work.

Time and money can be saved if we know what definitely constitutes a non-repairable tyre, so that it can be discarded without first being sent to the repair station.

Tyre Repair And Retreading


Repair is not recommended for any tyre that has:

Any evidence of breaks caused by flexing.

This type of damage is only too often associated with other damage that may not be visible.

Bead injuries to more than the chafers.

Any injury that would prevent the bead of a tubeless tyre sealing to the wheel.

Any evidence of separation between the plies of around the bead wire.

Any injury that would require a reinforcement.


Kinked or broken beads.

Weather or radial cracks in the sidewall that extend into the cord body.

Blister or other evidence of heat damage.

Cracked, deteriorated, or damaged inner liners or tubeless tyres.

These are only general criteria.

Before rejecting a tyre that is questionable, always seek expert advice.

Abrasion wears the tread away long before the carcass is worn out

It is standard practice for commercial aircraft tyres to be retreaded.

Tyre is thoroughly inspected by retreader.

The tread, sidewalls, and beads are checked for;

cuts,

bruises,

other damage, or

wear,

air is injected into the sidewall to check for any ply separation.


Checked for;

Fabric fatigue and

Indication of contamination by

oil,

grease, or

hydraulic fluid.

Old tread rubber removed by contour buffing

produces a smooth shoulder to shoulder surface.

New tread rubber and reinforcement are then applied to the buffed carcass,

Tyre is placed in a heated mould and cured.


After it is taken from the mould, balance patches are bonded to the inside of the tyre to achieve the proper static balance.

Tyre is then given a final inspection.

The tyre is identified as a retreaded tyre and a record made of the number of times it has been retreaded.

There is no specific limit to the number of times tyres can be retreaded.

Determined by the condition of the carcass.


All new and retreaded tyres should be stored in a; cool, dry area, out of direct sunlight and away from any electrical machinery. Fluorescent lights, electric motors, generators,

and battery chargers all convert oxygen into ozone, which is very harmful to rubber.

Tyre Storage

The storage room should not have extremes of temperature, but should be maintained between 32 and 80 F (0 and 27 C).

Special care should be taken to assure that no; grease, oil, hydraulic fluid,or any other hydrocarbon compound

comes in contact with the stored tyre, as all of these compounds will attack the rubber to some degree.

Tyre Storage

Whenever possible the tyres should be stored vertically in racks.

Tyre supported on a flat surface which is at least three or four inches wide.

Tyre Storage

If it is necessary to stack them horizontally,don't stack them more than; five tyres high, for tyres with a diameter of up to 40 inches, four tyres high for those between 40 and 49 inches, and three tyres high for tyres larger than 49 inches.

If tubeless tyres are stacked horizontally, the bottom tyres in the stack may be distorted so much that the beads will not

seat on the wheel unless a special bead-seating tool is used.

A great number of aircraft tyres are of the tube type.

Tubes for these tyres are either

unreinforced rubber for normal applications or

a special heavy‑duty reinforced tube

has a layer of nylon fabric melded to its inside circumference to protect it from chafing against the rim and from heat caused by brake application.

Tube construction and selection

Aircraft Tubes

All aircraft tubes are made of a specially compounded natural rubber that holds air with a minimum of leakage.

There are two primary causes for an aircraft tube leaking:

a hole in the tube, or

a defective valve.

It is extremely important that only the tube recommended for a particular tyre be used with it.

If the tube is too small for the tyre, its splices will be overstressed and the tube will be weakened

Aircraft Tubes

Tube construction and selection

If a tube is suspected of leaking,

first check the valve by spreading a drop of water over the end of the valve,

Watch to see if a bubble forms.

If a bubble does form, the valve core should be replaced.

Aircraft TubesTube Inspection

If the leak is not in the valve, the tyre must be deflated and demounted and the tube removed.

Inflate the tube and submerge it in water to find the source of bubbles.

If the tube is too large for the available water container, flow water over the surface of the tube as you look for the leak.

When inflating a tube that is not in a tyre, do not put more air into it than is required to round it out.

Check the tube carefully around the valve stem and the valve pad for any indication of the pad pulling away from the tube.


Examine the inside circumference of the tube for evidence of chafing against the toe of the bead or by corrosion on the wheel.

Any tube that is chafed enough to lose some of its thickness in spots should be replaced.


The brakes on a modern high‑performance aircraft absorb tremendous amounts of energy,

Some wheels have heat shields,

Tyres and tubes cannot be completely protected from the heat.

Examine the inner circumference of the tube for;

any indication that it has been heated enough for the rubber to have lost its smooth contour and taken a set or developed square corners.

Any tube that is deformed in this way should be replaced.

Reinforced tubes should be used on installations where there is enough heat to damage a regular tube.


Tubes should be stored in their original cartons whenever possible,

if their cartons are not available, they should be dusted with tyre talcum and wrapped in heavy paper.

Tubes may also be stored inflated by putting them in the proper size tyre and inflating them just enough to round them out.

The inside of the tyre and the outside of the tube should be dusted with tyre talc to prevent the tube sticking to the tyre.

Aircraft TubesTube Storage

Tubes should never be stored;

by hanging them over nails or pegs, or

supporting them in any way that would cause a sharp fold or crease,

these creases will eventually cause the rubber to crack.

Tubes with creases should not be put into service.

Tubes, like any other rubber product, should be stored in a cool dry, dark area, away from any electrical equipment that would produce rubber-damaging ozone.

Aircraft TubesTube Storage

Most modern aircraft use the split-type wheel,

Makes tyre mounting easier than

the single piece drop-centre wheel, or

wheels having a removable flange held on with a locking ring.

The maintenance manual must be followed in detail when mounting and demounting the tyres.

This information includes such details as

bolt torque,

lubrication requirements, and

wheel balancing details.

Tyre MountingTubeless tyres

Before the tyre is mounted on a wheel, the wheel must be carefully inspected to ensure;

no nicks or scratches in the bead seat area, could cause the air to leak, and

the area on which the O-ring between the wheel halves seals.

Carefully examine the entire wheel for

Corrosion, and

Any evidence of the finish being scratched through worn off,

Ensure that any balance weight installed when the wheel was manufactured is securely in place.

Check the thermal fuse plugs for security and condition, and

Air valve for the condition of its O-ring seal.


Clean the bead seat area and the O-ring seal area with a cloth dampened with isopropyl alcohol, and

Place the inboard wheel half on a clean, flat surface.

Check to be sure that the tyre is approved for the aircraft on which it is being mounted, and

The word TUBELESS is on the sidewall.

Ensure there is no foreign material inside the tyre, and

Wipe the bead area with a rag dampen with isopropyl alcohol.

Lubricate the O-ring with the same grease used for the wheel bearing, and

Carefully place the seal in the groove without stretching or twisting it.


Apply tyre talc to the toe, or inner edge, of the bead to help the bead to seat when the tyre is inflated.

Ensure that no powder gets between the bead and the wheel flange.

Carefully place the tyre over the inboard wheel half with the red dot indicting the tyre's light point adjacent to the wheel valve, (or if some other mark on the wheel identifies its heavy point, adjacent to that mark).

Place the outboard wheel half inside the tyre and line up the bolt holes.

Apply an anti-seize compound to;

the threads of the bolts,

both sides of the washers, and

the bearing surface of the nuts.


Install the bolts and nuts, and draw all of the nuts up in a crisscross fashion to one-half of the required torque.

Go back and bring them all up to the full torque.

Use an accurate hand torque wrench.

Never use an impact wrench on any bolt where the torque is critical,

Torque is applied in a series of blows or jerks, and the actual stresses to which the bolt is subjected are considerably greater than the bolt is designed to take.


Place the wheel and tyre assembly in a safety cage,

adjust the air pressure regulator to the recommended tyre pressure, and,

using a clip‑on chuck, inflate the tyre gradually.

Watch while the tyre is inflating to be sure the beads seat against the wheel flange.

All nylon tyres stretch when they are initially inflated and should be allowed to remain for 12 to 24 hours with no load applied.

This stretch may cause a five to ten percent decrease in pressure.

The pressure should be adjusted after this period.

Continue to monitor the inflation pressure daily.

There will be some pressure loss, but it should not exceed 5% in any 24-hour period.


Be sure before mounting a tube-type tyre on a wheel, that the tyre and tube are both correct for the installation.

Inspect the wheel for any indication of damage or corrosion, and if any corrosion is found, remove all traces of the damage and restore the protective oxide film.

Spray on two coats of zinc chromate primer and restore the finish to match the rest of the wheel.

Before mounting the tyre, clean the bead seat area with a rag dampened with isopropyl alcohol.

Check the inside of the tyre to be sure that it is clean and free of all foreign material and then dust it with an approved tyre talcum powder.

Tyre MountingTube tyres

Fold the inner tube and dust it with talc and slip it inside the tyre with the valve sticking out on the side of the tyre having the serial number.

Inflate the tube just enough to round it out and adjust it inside the tyre so the yellow mark indicating the heavy point of the tube aligns with the red dot on the tyre indicating its light point.

If there is no balance mark on the tube, you can assume that the valve is the heavy point.


Install the tyre and tube on the outboard wheel half so the valve stem sticks out through the hole in the wheel.

Rub tyre talc on the toe of the bead to help it slide over the wheel and seat itself.

Place the inboard half of the wheel in the tyre, but ensure that the tube is not pinched.

Lubricate the bolts with anti-seize compound and tighten the nuts in a crisscross fashion to one-half of the required torque.

Bring all of the nuts up to the recommended value with a good smooth pull on the handle of the torque wrench.


Tyre Mounting

Put the tyre in a safety cage,

Using a clip on chuck, gradually bring the air pressure up to the recommended value to seat the beads and then deflate the tyre.

Re-inflate it to the correct pressure.

This inflation, deflation, and re-inflation procedure allows the tube to straighten itself out inside the tyre and will remove any wrinkles from the tube.

Tube tyres

The air pressure in a tube-type tyre will drop after initial inflation.

the nylon plies stretch in the same way they do in a tubeless tyre, and there may also be air trapped between the tube and the tyre.

Inflation pressure will drop.

When all this trapped air leaks out around the valve, under the beads, and through the sidewall vents.

All of this air should be out within the initial 12- to 24-hour period.

Pressure may then be adjusted and the tyre put in service.


As aircraft takeoff speeds increase, the vibration caused by unbalanced wheels becomes annoying.

And this vibration is especially noticeable on nose wheels, since they extend quite a distance below the airplane on a slender strut, and they usually do not have a brake to help dampen the vibrations.

Tyre Balancing

After the tyre is mounted on the wheel, inflated, and allowed to take its initial stretch, the assembly is mounted on a balancing stand with the cones of the balancing shaft seating firmly against the bearing cups in the wheel.

Place the shaft on the balancing stand and allow the wheel to rotate until its heavy point comes to a rest at the bottom.

Tyre Balancing

Counterbalance the wheel with test weights until the assembly is balanced,

Install the correct amount of weight on the wheel at the location identified by the test weights.

Some balance weights are installed on special brackets that mount under the head of the wheel bolts,

Others fasten to the wheel rim by a cotter pin through holes that have been drilled in the rim for that purpose.

Tyre Balancing

Many of the smaller wheels do not have provisions for mechanically attaching balance weight

Lead strips having an adhesive backing may be used.

Use only the type of weight that is approved for the particular wheel being balancing,

Follow the instructions in the aircraft service manual for the installation of these weights.

Prevention of Creep

When in service, a tyre has a tendency to rotate (creep) around the wheel.

This creep, if excessive, will tear out the inflation valve and cause the conventional tyre to burst, with tubeless tyres it will cause deflation due to the seal being broken at the bead seat.

Creep is less likely to occur if the tyre air pressure is correctly maintained.

Prevention of Creep

Design features incorporated in wheels are:

Knurled Flange

The inner face of the wheel flange is milled so that the side pressure of the tyre locks the beads to the flange;

This method is not used for tubeless tyre wheels.

Prevention of Creep

Tapered Bead Seat.

The wheel rim is tapered so that the flange area is of greater diameter than that at the centre of the rim.

When the tyre is inflated, the side pressure forces the bead outwards to grip the rim.

this method is suitable for tubeless tyre wheels.

Creepmarks consisting of a yellow painted strip running across the edge of the rim and onto the tyre are also used.

Aircraft Landing WheelsAircraft wheels provide the mounting for tyres, which;

absorb shock on landing, support the aircraft on the ground, and assist in ground control during;

taxi, takeoff and landing.

Wheels are usually made from either aluminium or magnesium.

Either of these materials provides a strong, lightweight wheel requiring very little maintenance.

Aircraft Landing WheelsSingle piece, drop centre wheel.

Been replaced by the more popular two-piece wheel.

Tyres are removed and replaced on this type of wheel by prying them over the rim.

Aircraft Landing Wheels

Removable Flange The outer rim is removable and is held in place

when the tyre is inflated, with a snap ring.Care must be exercised when inflating a tyre on a

wheel with removable flange, If the snap ring is not properly seated, the flange can blow off and create a hazard to anyone standing nearby.

Aircraft Landing Wheels

Wheel assembly halves

High strength bolts

Hardened steel bearing races

‘O’ Ring

If too little torque is used on the axle nut, bearing cup to become loose and spin, enlarging its hole, and requiring a rather expensive repair to the

wheel. If the torque is too high,

the bearing can be damaged because the lubricant will be forced out from between the mating surfaces.

The amount of torque required vary with the installation,

Procedure used for installing and securing the axle nut must be that recommended by the airframe manufacturer.

Check for Axle Nut Torque

Before attempting to remove a wheel and tyre assembly from an aircraft using two piece rims, the tyre should first be deflated using a deflation cap before attempting to remove the axle nut.

If due to some extreme force being applied to the wheel rim on landing or take‑off, the bolts that hold the two rim halves together may have sheared then the only thing holding the complete assembly together will be the axle nut.

If the axle nut is untorqued while the rim is in the above state then there is a risk of serious injury and damage to the aircraft resulting from rapid deflation of the tyre.

Removal of Wheel and Tyre Assembly

Wheel Bearings

Tapered roller type

consist of

a bearing cone,

rollers with a retaining cage, and

a bearing cup, or outer race.

Each wheel has the

bearing cup, or race, pressed into place

hub-cap to keep dirt out of the outside bearing.

Suitable retainers are supplied inboard of the inner bearing to prevent grease from reaching the brake lining.

Felt seals are provided to prevent dirt from fouling multiple-disk brakes.

Seals are also supplied on amphibian aircraft to keep out water.

5-2Wheels and Tyres

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Transcript of 5-2Wheels and Tyres