welcome! michelin aircraft tire reliability, safety & performance
TRANSCRIPT
Welcome!
Michelin Aircraft Tire Reliability, Safety &
Performance
AGENDAProof 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 60 @ 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!
MaintainingProper 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 Casing plies tend to
scissor in relation to scissor in relation to each other creating each other creating heat.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:+60 112 134
156
Temperature Rise F +40 108 129 151
+20 104 125 145 Operating Pressure 100 120 140
-20 96 115 135
Temperature Drop F -40 92 111 129
-60 88 106 124
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 CriteriaSidewall Cuts
Tire must be changed whenever cords are
visible.
In Service Removal CriteriaWeather/Ozone Cracking
Looks bad but only
change if cord can be seen under the cracks
SummaryProof 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?