FAA 4

What are the 4 ways of classifying A/C tyres?

by type, ply rating, whether they are tube-type or tubeless, and whether they are bias ply tires or radials.

What is the other method used to identify a tyre?

By its dimensions

How many types of A/C tyres are still in production?

There are 4. (Type I, III, VII, VIII)

How are type III tyres designated?

It is designated by two number system. The first number is the nominal section width of the tire, and the second number is the diameter of the rim the tire is designed to mount upon

What is another name for Type VIII tyres?

three-part nomenclature tires.

How is a radial tyre shown in the nomenclature on the tyre?

It replaces the "-" with the letter R.

What does a B mean in the nomenclature of a tyre designation?

it means that the tire has a wheel rim to section width ratio of 60 to 70 percent with a bead taper of 15 degrees.

What does an H mean in the nomenclature of a tyre designation?

It means that the tire has a 60 to 70 percent wheel rim to section width ratio but a bead taper of only 5 degrees.

Is the ply rating of a tyre directly related to the number of plies in a tyre?

No, the number of plies used was directly related to the load the tire could carry.

How is a tubeless type tyre shown on the tyre wall?

 It have the word "Tubless" on it.

Can you put a tube in a tubeless type tyre?

Only if you consult the aircraft manufacturer’s maintenance information for any allowable tire damage and the use of a tube in a tubeless tire.

What is the difference between a bias play and radial ply tyre?

The difference is that the bias ply tire plies angles between 30 degrees and 60 degrees in relation to the direction of the tire while the radial ply tire pliers laid at a 90 degrees angle

What are reinforcing plies?

The single or multiple layers of nylon and rubbers on bias tires.

What is the main function of protector plies?

Help resist puncture and cutting while protecting the carcass body of the tire

The tread area of a tyre is made from a compound which is formulated to resist what 4 things?

To resist wear, abrasion, cutting, and cracking.

What are the two reasons for the grooves on a modern tyre tread?

To provide cooling and help channel water from under the tire in wet conditions to increase adhesion to the ground surface.

How would you identify if a tyre was within its wear limits (where would you find the data)?

in the manufacturers data.

Can an A/C tyre be re-treaded?

If approved by the manufacturer.

What is the main function of the tyre's sidewall?

To protect/protection.

What is the purpose of the green or white dots on the sidewall of a tyre?

This is to mark where the vent hole is.

Why is it not desirable for this gas to remain within the tyre?

Gas trapped in the plies could expand with temperature changes and cause separation of the plies, thus weakening the tire leading to tire failure.

What is the purpose of a Chine on an A/C tyre?

The chine diverts runway water to the side and away from the intake of the engines.

When should the tyre pressure be checked?

Tire condition is inspected while mounted on the aircraft on a regular basis.

Where would you find the correct tyre pressure for an A/C tyre?

 In the aircraft manufacturer’s maintenance data.

What is the result to a tyre if it is under inflated on landing?

An underinflated tire may flex beyond design limits of the tire. This causes excessive heat build-up that weakens the carcass construction.

How often would you check an A/C's tyre pressure?

Tire pressure must be checked and maintained within the proper range on a daily basis or before each flight if the aircraft is only flown periodically.

What temperature should the tyre be when carrying out a pressure check?  Why?

Tire pressure should be measured at ambient temperature because a sudden change in ambient temperature greatly affects tire pressure and complicates maintenance of pressure within the allowable range for safe operation.

Apart from overheating, what are 4 other reasons to ensure a tyre is always correctly inflated?

 It leads to premature tire replacement. They may also creep or slip on the wheel rim when under stress or when the brakes are applied.  It can pinch the sidewall between the rim and the runway causing sidewall and rim damage. Damage to the bead and lower sidewall area are also likely.

f a tyre has been properly maintained, where should it reach its wear limits first?

At the centerline of the tire.

Where would you expect to find the proper wear limits for a particular tyre

 In the manufacturer instructions specific to the aircraft

Is it a requirement to change a tyre which is showing signs of uneven wear?

Yes, it should be investigated and corrected.

What other faults, apart from wear, should you be looking for during a tyre inspection?

Cuts, bruises, bulges, imbedded foreign objects, chipping, and other damage.

What could be the result of a tyre having a "flat spot" that exposes the reinforcing plies?

It is the result of the tire skidding on the runway surface while not rotating

What should you do when you find a bulge in a tyre?

Immediately remove it and replace it

What is the remedial action when a tyre comes into contact with fuel, oil, hydraulic fluid or other solvents?

You wash the tire or area of the tire with denatured alcohol followed by soap and water. Removed from service

Why should you always mark the tyre with chalk in the area of damage prior to removal of the tyre from the wheel?

As it could easily become undetectable without air in the tire.

On a suspected damaged tyre that has been overheated, what are the safety precautions for approaching the tyre?

 Never approach a tire while its temperature is still elevated above ambient temperature/ overheated.

Approach a damage tire and wheel assembly from an oblique angle advancing toward the shoulder of the tire.

What is the first procedure to be carried out prior to wheel assembly removal from an A/C?

Deflate all unserviceable and damaged tires before removal from the aircraft

Where would you find the proper technique for removing the tyre bead from the rim?

The wheel manufacturer’s maintenance information is the primary source for dismounting guidelines.

Should all tyres be sent for re-treading?

No

What are 5 of the safety precautions with storing and handling A/C tyres?

1.  tire should always be stored vertically so that it is resting on its treaded surface.

2. If horizontal stacking of tires is necessary, it should only be done for a short time.

3. Tires should be stored away from strong air currents that continually present a supply of one or both of these gases (Ozone and Oxygen)

4. storage should be at cool temperatures to minimize degradation.

5. Never stack aircraft tires horizontally for more than 6 months.

What are 4 of the precaution for storage and handling of tyre tubes?

1. An aircraft tire tube should be kept in the original carton until put into service to avoid deterioration through exposure to environmental elements.

2. Regardless of storage method, always store aircraft tubes in a cool, dry, dark place away from ozone producing equipment and moving air.

3. When handling and storing aircraft tire tubes, creases are to be avoided.

4. Never hang a tube over a nail or peg for storage.

What should be used to lubricate the tube to tyre interface?

Non-hydrocarbon lubricant specified. Talc.

What does a red dot indicate on a tyre?

The heavy spot

What is the main safety precaution when first inflating a tyre after assembly?

The tire must be placed in a tire inflation safety cage and treated as though it may explode due to wheel or tire failure.

What are the two types of hydroplaning?

1.  Dynamic Hydroplaning - Water building up in front of the tire provides a surface for the tire to run on and contact with the runway surface is lost.

2. Viscous hydroplaning - occurs on runways with a thin film of water that mixes with contaminants to cause an extremely slick condition.

What effect on tyre wear does a cross-cut runway have?

Crosscut runway surfaces drain water rapidly but increase tire wear.

What are the safety precautions when cleaning wheel bearings?

The bearings should be removed from the wheel to be cleaned with the recommended solvent, such as varsol, naptha, or Stoddard® solvent.

-Never rotate the bearing while drying with compressed air.

-Always avoid steam cleaning of bearings.

What is the generally recommended way of lubricating a wheel bearing?

Use of a pressure bearing packing tool or adapter is also recommended as the best method to remove any contaminants from inside the bearing that may have remained after cleaning.

What material is an A/C wheel made from?

Aluminum or Magnesium alloy.

What type of construction is a modern A/C wheel?

Two piece construction

What part of an A/C rim is the most critical area?

The bead seat area

What does the inner wheel half have as part of its construction that the outer does not?

The inboard wheel half must have a means for accepting and driving the rotor(s) of the aircraft brakes that are mounted on both main wheels.

On a high performance or heavy A/C, what other item is installed into the wheel hub?

Thermal Plugs

If the thermal (fusible) plug has melted, what must happen to the wheel assembly?

It Deflates the tire. The tire must be removed from service, and the wheel must be inspected in accordance with the wheel manufacturer’s instructions before return to service if a thermal plug melts.

Why is axle nut torque loading so important?

If the nut is too loose, the bearing and wheel assembly may have excessive movement.

-An over-torqued axle nut prevents the bearing from properly accepting the weight load of the aircraft.

What is the first thing you should do be removing an A/C wheel assembly from an A/C?

Deflating the tire.

What is the safety precaution when deflating an A/C tyre?

Do not stand in the path of the released air and valve core trajectory when removing air from the tire as it could seriously injure the technician should it release from the valve stem.

What is the correct method for releasing the bead of a tyre from a wheel hub (fig. 13-63)?

A mechanical removal tool designed for breaking the bead can be used. Examples are the Hydraulic press and Arbor press

What precautions need to be exercised when cleaning wheel parts? Why?

Avoid abrasive techniques, materials, and tools, such as scrapers, capable of removing the finish off of the wheel because Corrosion can quickly form and weaken the wheel if the finish is missing in an area.

why should you never steam clean a bearing?

The surface finish of the metals will be compromised leading to early failure.

What are the 7 faults commonly found with bearings when being inspected?

1. Galling

2. Spalling

3. Overheating

4. Brinelling

5. Bruising

6. Staining and surface marks

7. Etching and corrosion

What is the usual method of finding cracks when carrying out wheel half bead seat inspection?

The Eddy current inspection

What inspection technique can be used to find cracks in the brake disc drive key areas?

Dye penetrant test

What is the limit of movement between a brake drive key and the wheel half?

There should be no movement.

What is the purpose of a fusible plug?

It deflates the tire. To release air from the tire should the temperature rise to a dangerous level.

What are the 3 purposes of A/C brakes?

1. For safe operation of the aircraft on the ground.

2. The brakes slow the aircraft and stop it in a reasonable amount of time.

3. They hold the aircraft stationary during engine run-up and, in many cases, steer the aircraft during taxi.

What wheels normally have brakes fitted?

The main wheels

What is the most common form of brakes on modern A/C?

 Disc Brakes

How is a brake disc able to move on a floating type brake assy?

the brake disc is keyed to the wheel. It is free to move laterally in the key slots.

What prevents brakes from dragging?

When the brakes are applied, the pistons move out from the outboard cylinders and their pucks contact the disc. The disc slides slightly in the key slots until the inboard stationary pucks also contact the disc.

 What stops the brake piston from retracting all the way back in the housing as the brake pad wears?

When it gets contact to the adjusting pin.

What is a secondary function for the adjusting pin?

t serves as a wear indicator.

What are the two main differences between the floating and fixed disc type brake assy's?

1. The fixed disc type brake must have an even pressure on both sides of the disc brake to generate the required friction while the floating disc brake only put pressure on one side of the disc to generate friction.

2. In a floating disc brake, the brake disc is keyed to the wheel where it is free to move laterally while the fixed type doesn’t.

What are the regular maintenance requirements for a typical brake unit?

-Regular inspection for any damage and for wear on the linings and discs.

-Replacement of parts worn

-The braking action for each main wheel should be equal with equal application of pedal pressure.

What method is normally used on a multiple disc brake to compensate for wear of the rotors and stators?

 The adjuster traps a predetermined amount of fluid in the brakes that is just sufficient to provide the correct clearances between the rotors and stators.

What is the main advantage of a segmented disc brake over a solid disc brake?

 Segmented Disc brake does much better in dissipating the heat generated from slowing down the rotation of the wheels on large and high performance aircraft.