h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I read some where that the tyres on these jumbo jets have a very short life span?
I have a question about this,=
Would it make a difference to the life span of the tyres if the wheels were spinning before the plane touched down?
I mean, they could be driven by a motor connected to the main engines, that meant that the tyres would not have that sudden burst of contact with the rnnway upon landing. The spinning of the wheels would generate heat, thus the tyres would not go from ambient to hot during landing.
This may also cut down slowing down time for the plane after landing, as the plane could be slowed down by the wheels as well as main engines.

Again during take off, the wheels being driven at a speed in line with the plane, would shorten take off time, thus less friction contact with the runway.
Would this be feesable? or do I need to update my medication
Smudger,

Update your medication Smudger!

The amount of energy requires to get the wheels spinning at sufficient speed to make a a difference would not be cost effective. It would need some complex calculations to get the wheels spinning at the appropriate speed.

Assuming that an aircraft touched down at at the same air speed every time, which is doesn't, the ground speed would vary a lot depending on the wind speed.

Oh yes, the wheels are used for braking during touch down. The have hydraulic brakes just the same as your motor vehicle. The energy dissipated bringing the wheels up to speed will have some effect in slowing the aircraft down.

Driving the wheels during take of is not feasible either. It all to do with inertia and the main engines are better at coping with that. If you did drive the wheels the chances are they would just spin and burn more rubber than landing does.

Ah! well Donald, it was just an idea I had
Now I know the reasons why its never been done, I will go and increase my meds
Smudger,

Actually, you wouldn't even need a motor to get the wheels spinning, just attach some kind of wind driven turbine onto the side of the wheel (think miniature waterwheel) and that would get the wheels spinning before the aircraft touched down at no extra cost (oh and theoretically the spinning up the wheels would actually slow the aircraft down in the air ever so slightly - ofsetting the braking advantage of them skidding on the ground.

Quick! Off to the patents office!

You would need to do a cost-benefit analysis involving the cost of the component (pretty big - them wheels ain't small), the extended life of the tyre, and the opportunity cost of the weight of the new component (in terms of additional fuel required to get the plane off the ground, and all the passengers/luggage/freight that you can no longer carry due to the weight of the component).

And you'd find that it ain't worth it. Cos if it was, you'd find them fitted as standard on all planes.

RF

Right, got it now
Its just that I thought that when I see them land, I always see that puff of smoke which must be hard wearing on the tyres.
If you drive a car like that you would be lucky to get a fraction of the milage out of it?
Smudger,