Welcome! Michelin Aircraft Tire Reliability, Safety & Performance

AGENDA  Proof of the need……  INFLATION PRESSURE! –initial inflation –pressure monitoring –pressure effects  Controls for Tire Damage: FOD

Proof of the need: Learjet 60 Crash – CAE?

Proof of the need: Concord?

Learjet CAE: Tire Related? Tire pieces begin at 2300 feet after takeoff roll. Rim scar marks began at 5200 feet thru end of runway. All four tires destroyed. Only tire beads remained on wheel remnants

Tire Related? Causes/Responses: –Preventative? –Reactive? Let us focus on prevention. Success here prevents a “Reactive” response by the pilots.

Tire Related? Most common causes for tire failure events: – Over-deflection (under-inflated) – Foreign Object Damage (FOD) – Fuze plug release (dragging brake heat) – Stripped ribs due to high lateral forces (high speed turn-out)

Tire Related? Most common causes for tire failure events: – Over-deflection (under-inflated) – Foreign Object Damage (FOD) – Fuze plug release (dragging brake heat) – Stripped ribs due to high lateral forces (high speed turn-out)

Tire Related? The single most important thing to prevent tire related incidents is – Inflation Pressure!

Maintaining Proper Inflation Why is it important?

Under-Inflation May Cause: Vibration (bias type) Wheel Slippage Tire/Wheel damage Irregular shoulder wear Faster wear rate Thrown tread/Tire failure

Over-Inflation May Cause: More susceptibility to FOD damage Increased wear rate (less contact patch) Irregular wear in the center ribs

Deflection Definition: The difference between the unloaded and loaded tire section heights Typical Deflection Trucks: 12% Cars: 18% Aircraft: 32%

Bias/Radial Comparison Bias Tire The tread flexes with the tire: –Contact patch deforms –Contact patch moves –Casing plies tend to scissor in relation to each other creating heat. Radial Tire Sidewalls and tread function separately; tread is not affected by sidewall flexing: –Contact patch doesn’t deform –Less movement in the contact patch –No movement between nylon plies

Why is inflation pressure Important? Normal Footprint Notice the squirm

Severely over-loaded/under inflated

Pressure Effects: Loss vs Temp. Rule: Pressure change 1% per each 5 Example Calculation: Temperature Rise F Operating Pressure Temperature Drop F

Tire Related? Most common causes for tire failure events: – Over-deflection (under-inflated) – Foreign Object Damage (FOD) – Fuze plug release (dragging brake heat) – Stripped ribs due to high lateral forces (high speed turn-out)

In Service Removal Criteria Cuts/FOD damage to tread area: –Injury severs or extends across a rib –Undercutting at base of any cut –Round objects >3/8” dia. –Reaches carcass/belt plies

In Service Removal Criteria Sidewall Cuts Tire must be changed whenever cords are visible.

In Service Removal Criteria Weather/Ozone Cracking Looks bad but only change if cord can be seen under the cracks

Summary  Proof of the need……  INFLATION PRESSURE! –initial inflation –pressure monitoring –pressure effects  Controls for Tire Damage: FOD

Safety First When working on or around aircraft tires, following established safety procedures is critical Aircraft tire and wheel assemblies operate under high pressures in order to carry the loads imposed on them – treat them with the same respect that any other high pressure vessel would be given

For More Information Michelin ® Aircraft Tire Care & Service Manual and Engineering Data Book –Available on CD or in print Certified Tire Expert Programs Levels I & II –Available on CD or in print Call us!

Questions?