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.