Tyre Use - Wheels & Tyres - Airframes & Aircraft Systems #21

Summary

This lesson delves into tire-related aviation issues, focusing on aquaplaning, a phenomenon where water builds up under the tire, causing loss of contact with the ground. It teaches how to calculate aquaplaning speed based on tire pressure and emphasizes the importance of monitoring tread depth to prevent it. The lesson also addresses tire wear, damage assessment, and the significance of tire creep, which is the movement of a tire on its rim. It introduces methods to detect creep and the process of tire retreading, highlighting the economic and safety benefits of repairing and retreading tires over replacing them.

Takeaways

• 💧 Aquaplaning occurs when a wedge of water builds up under the tire, causing a loss of contact with the ground.
• 📏 The aquaplaning speed can be calculated using the formula: aquaplaning speed = 9 * √P (psi) or 34 * √P (bar or kgf/cm²).
• 📉 The risk of aquaplaning increases as tire tread depth decreases, emphasizing the importance of tread assessment.
• 🔥 Applying brakes during aquaplaning can generate enough heat to potentially melt the tire tread.
• ⚠️ Pre-flight tire inspections should include checks for cuts, bulges, embedded foreign objects, wear, creep, and local sponginess.
• 🚫 Tires with cuts penetrating to the cords are unserviceable and must be replaced if the fabric is fractured.
• 🛑 Flat spots on tire treads, especially from skidding or aquaplaning, should be carefully examined for fabric weakening.
• 🔄 Tire creep is the movement of a tire on the rim after fitting, which can be monitored using painted marks on the wheel and tire.
• 🔧 Damaged aircraft tires can often be repaired or retreaded, saving costs compared to purchasing new tires.
• 🏗️ Retreading and repairing aircraft tires must be done at certified stations by qualified technicians to ensure safety regulations are met.

Q & A

What is aquaplaning or hydroplaning?

Aquaplaning or hydroplaning is a phenomenon where a wedge of water builds up under the tread of the tire, causing it to lose contact with the ground.

How is the aquaplaning speed calculated?

The aquaplaning speed can be calculated using the formula: aquaplaning speed equals nine times the square root of P (in psi) or 34 times the square root of P (in kgf/cm² or bar), where P is the tire pressure.

What factors increase the possibility of aquaplaning?

The possibility of aquaplaning increases as the depth of the tread is reduced, so it's important to accurately assess the amount of tread remaining.

What happens when a tire aquaplanes?

When a tire aquaplanes, the coefficient of dynamic friction between the tire and the ground reduces to very low values, typically near zero, making nosewheel steering and braking ineffective.

What can the heat generated during aquaplaning do to a tire?

The heat generated between the tire and the water, especially if the brakes are applied during aquaplaning, may be sufficient to melt the tread of the tire.

What should be checked during a pre-flight tire inspection?

During a pre-flight tire inspection, one must examine tires for cuts, bulges, embedded stones, metal or glass, signs of wear, creep, and local sponginess.

What is considered normal tire wear?

Normal tire wear includes the presence of wear bars or red markers worn to the base of the marker grooves or to the casing cords, indicating it's time for replacement.

What is tire creep and why is it a problem?

Tire creep is the movement of a tire slightly around the rim after it's first fitted to a wheel. Excessive creep can lead to damage, such as tearing out the inflation valve and causing a tire burst.

How is tire creep monitored?

Tire creep is monitored by painting white lines, known as creep marks, one on the wheel and a matching one on the tire. Misalignment of these marks indicates creep.

Can damaged aircraft tires be repaired or retreaded?

Yes, many aircraft tires that become damaged in service can be successfully repaired, and those with worn-out treads but an intact carcass can be retreaded.

What is the benefit of retreading aircraft tires?

Retreading aircraft tires can save aircraft operators considerable sums of money as it is much cheaper than replacing with new tires and is a common practice.

Outlines

00:00

🚗 Tire Safety and Aquaplaning

This paragraph discusses the issues related to tire wear, damage, and the phenomenon of aquaplaning or hydroplaning. It explains how aquaplaning occurs when a wedge of water builds up under the tire, causing a loss of contact with the ground. The aquaplaning speed can be calculated using a specific formula based on tire pressure. The paragraph also highlights the importance of accurately assessing tire tread depth and the risks associated with reduced tread, such as increased likelihood of aquaplaning and reduced effectiveness of steering and braking. It also addresses the need for pre-flight inspections to check for tire damage and the criteria for determining if a tire can be repaired or must be replaced.

05:01

🛫 Tire Wear, Creep, and Retreading

The second paragraph focuses on the increased tire wear due to larger taxi distances at airports and recommends maintaining a speed limit to minimize wear. It defines 'creep' as the movement of a tire on the rim after fitting, which is normal initially but can lead to problems if it persists. The paragraph explains how to monitor creep using painted lines and the consequences of misalignment. It also touches on the possibility of repairing and retreading aircraft tires, which can save money for operators. The importance of certified technicians for retreading and repairing tires is emphasized, and the paragraph concludes with a reminder of the importance of understanding tire wear limits and the monitoring of creep.

Keywords

💡Aquaplaning

Aquaplaning, also known as hydroplaning, is a phenomenon where a layer of water builds up under the tire, causing it to lose contact with the ground. This is particularly dangerous as it can lead to a loss of steering and braking control. In the script, aquaplaning is discussed as a significant safety concern for aircraft tires, with a formula provided to calculate the aquaplaning speed based on tire pressure. The importance of maintaining proper tire tread depth to prevent aquaplaning is also emphasized.

💡Tire Wear and Damage

Tire wear and damage refer to the gradual deterioration and potential structural issues that can occur in tires over time or due to specific incidents. The script discusses the importance of inspecting tires for cuts, bulges, embedded foreign objects, and signs of wear or damage. It also mentions that certain types of damage, such as cuts penetrating to the tire's cords, render the tire unusable and require replacement.

💡Tire Creep

Tire creep is the movement of a tire on its rim after it has been fitted, which can be normal initially but can become a problem if it continues over time. The script explains that excessive creep can lead to issues such as tearing out the inflation valve and causing a tire burst. It also notes that creep is less of an issue with tubeless tires if the tire bead is undamaged and the pressure is correctly maintained.

💡Tire Pressure

Tire pressure is a critical factor in tire performance and safety. The script mentions that tire pressure affects the risk of aquaplaning, with a formula provided to calculate the aquaplaning speed based on this pressure. It also suggests that maintaining correct tire pressure can help prevent issues like tire creep and excessive wear.

💡Tread Depth

Tread depth is the measurement of the tire's tread, which provides grip and contact with the ground. The script highlights that reduced tread depth increases the likelihood of aquaplaning and that it is important to accurately assess the remaining tread to ensure tire safety. It also discusses wear indicators and the importance of not using tires where the tread is worn down to the casing cords.

💡Dynamic Friction

Dynamic friction is the force that opposes the motion of an object when it is in contact with another surface. In the context of the script, the coefficient of dynamic friction between the tire and the ground is mentioned as reducing to very low values during aquaplaning, which can result in a near-zero friction coefficient, making steering and braking ineffective.

💡Retreading Tires

Retreading is the process of applying a new tread surface to a worn tire, allowing it to be reused. The script explains that many aircraft tires can be successfully retreaded, which can save operators significant costs compared to purchasing new tires. It also notes that retreading and repairing must be done in certified facilities by qualified technicians.

💡Pre-Flight Inspection

A pre-flight inspection is a critical safety procedure that includes examining various components of an aircraft, including its tires. The script outlines the need to inspect tires for various forms of damage and wear during this process to ensure flight safety.

💡Tire Bead

The tire bead is the part of the tire that seats against the rim of the wheel. The script mentions that the condition of the tire bead is important in preventing issues like creep, especially in tubeless tires. A damaged bead can lead to problems such as tire burst due to excessive movement of the tire on the rim.

💡Tire Cord

Tire cords are the reinforcing fibers embedded in the rubber of the tire that provide strength and structure. The script describes how cuts in the tire that penetrate to the cords render the tire unusable, as these cords are essential for the tire's integrity.

Highlights

Discussing the problems of creep and aquaplaning or hydroplaning.

Aquaplaning is caused by a wedge of water building up under the tire tread.

Aquaplaning speed can be calculated using a specific formula.

The possibility of aquaplaning increases as tire tread depth reduces.

Tire tread depth must be accurately assessed to prevent aquaplaning.

Aquaplaning results in a very low coefficient of dynamic friction.

Nosewheel steering and braking are ineffective during aquaplaning.

Heat generated during aquaplaning can potentially melt the tire tread.

Tires must be examined for various damages during pre-flight inspection.

Cuts in the tire that penetrate to the cords render the tire unserviceable.

Bulges in tires may indicate a partial failure of the casing.

Flat spots on tire tread caused by skidding or aquaplaning must be carefully examined.

Foreign bodies embedded in tires must be removed and assessed for damage.

Tire wear limits are indicated by marker grooves or cords.

Tires with visible fabric layers in the tread can continue in service.

Tire wear is increased by the larger taxi distances at modern airports.

Tire creep is a normal phenomenon when a tire is first fitted to a wheel.

Excessive creep can lead to tire damage and the need for replacement.

Creep marks are used to detect and monitor tire creep.

Aircraft tires can be successfully repaired or retreaded if the carcass is intact.

Retreading and repairing aircraft tires can save significant costs compared to new tires.

Retreading and repairing must be performed by certified technicians.

Transcripts

in this lesson we will discuss the

problems of creep

and if aquaplaning or hydroplaning we

will look at tire wear and damage we

will examine the problem of tire creep

and see how it is monitored

to end the lesson we will take a quick

look at the process of retreading tires

aquaplaning or hydroplaning is a

phenomenon caused by a wedge of water

building up under the tread of the tire

and breaking its contact with the ground

aquaplaning speed measured in nautical

miles per hour or knots is the speed at

which the tire loses contact with the

ground it can be found by applying the

formula

aquaplaning speed equals nine times the

square root of P where P is the tire

pressure in pounds per square inch

or aquaplaning speed equals 34 times the

square root of P where P is the tire

pressure in kilograms per square

centimeter or bar

the possibility of aquaplaning increases

as the depth of the tread is reduced it

is therefore important that the amount

of tread remaining is accurately assess

the coefficient of dynamic friction

between the tire and the ground will

reduce the very low values typically 0

when aquaplaning

neither nosewheel steering nor braking

will be effective when the wheels

aquaplaning

the heat generated between the tire and

the water if the brakes are applied

during aquaplaning may be sufficient to

melt the tread of the tire

here you may try an aqua planing

calculation enter a tire pressure

between 50 and 300 psi calculate the

aquaplaning speed and enter it in the

box

press go to check your calculation

you

during your pre-flight inspection tires

must be examined for cuts bulges

embedded stones metal or glass signs of

wear creep and local sponginess

cuts in the tire penetrating to the

chords render the tire and serviceable

the cords will be recognizable as pieces

of white fibrous material embedded in

the rubber of the tire

whether the tie can be repaired or must

be renewed is governed by the depth of

the cut

bulges may indicate a partial failure of

the casing if the casing has failed that

is to say the fabric is fractured and

the tire must be replaced any flat spots

on the tire tread especially those

caused by skidding or aquaplaning must

be examined with great care to determine

if the fabric of the tire has been

weakened unduly

foreign bodies such as pieces of metal

or glass or stones embedded in the tire

must be removed and the cuts probed with

a blunt tool by a technician to

ascertain their dabs

or renewal of the tire is governed by

the extent of the damage

if you are in any doubt about the

serviceability of a tire have it checked

before flight by a suitably qualified

technician

the amount of wear that a tire can be

subject to there is with different tire

types

some tires have market Aybar's in the

center groove on others the center

groove or the two grooves either side of

Center are used as wear indicators

generally patent red covers worn to the

base of the marker grooves or to the

marker tie bars for 25% of the tire

circumference or plain tread covers worn

to the casing cords must not be used

the special high-speed applications some

tires have a layer of fabric woven into

the tread these tires will have

reinforced red printed on the sidewall

this fabric may become visible during

normal wear this is perfectly normal and

the tire can continue in service with

this layer visible

with the increased size of modern

airports taxi distances have also

increased thus increasing the amount of

tire wear and risk of damage

to minimize tire wear it is recommended

that a speed of no more than 25 miles or

40 km/h should be reached during the

taxi run

when a tire is first fitted to a wheel

it tends to move slightly around the rim

this phenomenon is called creep and at

this stage it is considered normal

to the tire settles down however this

movement should cease

in service the timeI tend to continue to

creep around the wheel if this creep is

excessive on a tire fitted with an inner

tube it would tear out the inflation

valve and cause the tire to burst

creep is less of a problem with tubeless

tires as long as the tire bead is

undamaged and any pressure drop is

within limits creep is less likely to

occur if the tire gas pressure is

correctly maintained

in order to detect creep to white lines

known as creep marks are painted one on

the wheel and a matching one on the tire

if the lines become misaligned then the

tire is suffering from creep provided

the marks overlap each other the tire

can remain in service if however the

marks become completely misaligned then

the tire must be changed

many aircraft tires that become damaged

in service can be successfully repaired

tires of which the treads are worn out

flat spotted or otherwise damaged but of

which the core body or carcass is intact

can be retreaded

repairing aircraft tires has been a

common practice for many years and can

save aircraft operators considerable

sums of money

tires can be retreaded or repaired for

continued service at a cost much lower

than that of a new tire

Yaser 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 and

certified technicians

you should now have a good understanding

of how much tire wear and damage is

acceptable

the aquaplaning formula is quite

important but probably more important is

the fact that if the tire is aquaplaning

then its coefficient of friction is at

or near zero

you should understand the problems

associated with creep and how it can be

monitored

finally remember that an aircraft tire

whose tread is worn beyond limits could

normally be repaired or retreaded many

times

you