View Full Version : tyre pressures on landing?
I know that a 747-400 has a main gear tyre pressure of approx 200psi, but what does it rise to on the moment of impact with the runway? Anyone ever looked at EICAS at that moment? I'd be interested to know that's all, anyone know what the absolute pressure limit is for those kind of tyres before they go bang?!
supercarb
10th Feb 2004, 08:09
Qualification test for tyres requires them to withstand 4x the rated pressure for 3 seconds without failure.
The contact patch area times the pressure must equal the force between the tire and the runway.
Look at the deformation of the wheels, and the decrease in volume will give you an idea about the increase in pressure - i e not much.
There's bound to be some interesting shockwaves bouncing around in there though. Anyone know where there is more to read on that subject?
Cheers,
Fred
The vast majority of wheel/tyre heat is generated due to the heat dissipated when braking.
Also due to the latent effects the maximum temperature of the air in the tyre is not achieved until the a/c is parked up on stand (assuming a normal landing of course:} )
The temperature increase on landing would be influenced by the amount of compression, which as has been stated is not that large.
supercarb
11th Feb 2004, 21:31
For most aircraft types the maximum load experienced by the tyre occurs during the takeoff roll rather than on landing. In fact it is the combination of sustained load and high rolling speed that occurs on takeoff that is usually the critical design case for the tyre.
As well as braking, heat is generated within the tyre itself during rolling under load, which can result in significant heat build-up in the carcass during a long taxi roll.
Some useful reading matter can be found here:
Goodyear tyre care & maintenance manual (http://www.goodyearaviation.com/tirecare.html)
(See in particular the section 'Effects of Operating Conditions')