Spinning wheels

[uplander]

Here's something I've always thought about but never took the time to sit down and design, patent, sell, and make a million bucks on. Probably because it won't work, so please prove me right. (Apologies if this has been discussed before.)

You know all that rubber that coats the two ends of the runways at the touchdown points, where the tires make that beautiful puff of smoke. How much life does each landing take out of those tires? To avoid that, wouldn't it be logical to have the wheels rotating at approximately ground speed just before touch down? Then the rubber burn would just be due to the difference in wheel speed to ground speed.

I never see any wheels rotating just before landing, so I figure the brakes must be on. But why? One way to get them to rotate would be to build simple fan blades into the rims of the wheels, if there's room. The blade angle would have to be calculated to make the air spin the outer edge of the wheels at the air speed. I'm not sure if it can even get that fast, but even close enough to the air speed would be good.

OK, so why wouldn't this work?

[Ari707]

I have thought of that also never knew why either...

[Jonesbeach]

I think Anet had a discussion about this some time ago. The main response was that the cost of carrying around the fans is not worth the saving in rubber. Also, some one said that the most wear and tear on the tires is from turning while taxiing. I'm not sure if all this info is correct, but that's what I remember.

Steve

[Mateo]

The wheels aren't rotating on landing because no force has been applied to make them spin. The brakes are NOT on. If the brakes were on at touchdown, the tire would blow instantly from the force of being scraped across asphalt at 150kts without any way to dissapate the energy (like rolling). SOP on most small retractables is to tap the brakes just after rotation so that you don't have spinning wheels in the wells. I believe some transport-class aircraft do this automatically.

[nwafan20]

Well, airports would like that, at DTW, they have to "De-Rubber" the runway every 3-6 months or so, they do this by spraying it with a acid mix, and after they do this they need to repaint the part they de-rubberized, it would save them a lot of money.