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At the point of touchdown, an enormous cloud of smoke is created as the non-rotating undercarriage tyres hit the runway at a relative speed of, say, 200mph, and skid as they get up to speed. I know this results in rapid tyre wear, and I'm guessing it makes the landing less stable than it would be if
the tyres were spinning, and deposits rubber on the runway to the detriment of future landings.
Suppose the undercarriage wheels had radial vanes, and that the top half of the wheel was protected in front by a streamlined cowl. The air striking the lower vanes would spin the wheel up to a certain rpm as soon as the undercarriage was lowered, the rpm being proportional to airspeed. By using the correct size of vane, it should be possible to arrange for the relative speeds of the tyre surface and the runway to be relatively small (theoretically zero), assuming zero windspeed. (Clearly a headwind will increase the rpm and leave ground speed unaffected, so a difference will arise, but much less than with the current 'stationary wheel' arrangement).
I can't see the vanes causing problems on take-off: again for zero headwind there would be zero drag, and in a headwind situation I can't see them adding significantly to the total drag of the aeroplane. Once off the ground the wheels would be spinning pretty fast, and it may be that their bearings need uprating for higher rpm, but probably (max airspeed with gear down) with no weight on the wheels is easier on the bearings than the landing process.
Once the gear is raised, the wheels can either be left to spin down or braked.
Aeroplane Wheel Turbines
http://www.halfbake..._20Wheel_20Turbines
Great idea, but redundant and so [marked-for-deletion] [hippo, Oct 11 2002]
Baked in the late 40's early 50's
http://www.sensorsm.../0300/14/main.shtml
The special tires made the aircraft very hard to turn [IVnick8or, Oct 12 2002]
[link]
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And I thought this would be about an exiting new jam ... |
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We did do this before, at some length with a lot of high quality technical input. But the thread seems to have been deleted. |
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The conclusion was that while the technology existed, and indeed had been used, it was not useful/economic. |
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And would make those cutaway movie sequences of 'planes touching down with smoke billowing behind from the tyres much less fun. |
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Would have been funnier if it were a call for preservation of English English.
"Preserve Aeroplane Tyres -
Don't Buy Airplane Tires!" |
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I sent this in to my airline employer as a suggestion about ten years ago (thumbs down), though without a cowling: the vanes were angled so only the lower vanes catch the wind. This idea seems to pop up here every few months |
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[UnaBubba] 50lb Fiat X1/9. |
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In a cross-wind, wouldn't all the tires on one side be spinning at a different rate than the ones on the other? Wind gusts could spin up (or slow) certain tires, too. Might be a problem in a storm, or icy conditions. The way they do it now, at least the spin rate is identical on touchdown. |
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I didn't realize that this was a problem requiring so much attention.. |
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Tried, and hated, by airline pilots from the late 40's and early 50's. Seems the tires act like gyroscopes and make the aircraft hard to turn. [link] |
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Wow, great find, that link, [IVnick8or]. |
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Thanks [bris] pays to be a pilot, huh? |
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4n8: I posted that link on another newsgroup and it got some interesting feedback. Some pilots think that the stationary tires contribute a 5 to 10kt. reduction in air
speed on rollout and like that fact, and another point would be to hold the brakes, locking the wheels, until short final. |
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