I know what sublimation is Fred, and I allso know how great the difference has to be to get it to work in practical therms. It's true that in certain met conditions you can get sublimation from rwy or twy surfaces, but that's in the conditions when you don't need it. (That's the B...... part)
The time you need runway the most, is in conditons with percipitation, and you don't get sublimation that counts in those conditions. I you don't belive me, fine, but I work ATC at a arctic training base, and have ambient air and runway temp sensors in my console. Runway core temp allways "lag" after the air temp, and it's not uncommon that the runway is up to 10 degreees warmer then the surroundings for several hours. Let's say we have about -5 in the core, and -18 in the air. The only thing that happens in dry air conditions, is that rime form on the surface. (Should not happen, should it? In theory, but it does. ) During percipitation you get reduced friction whatever you have in the core, sublimation is not the issue, the rate of perciptiation is.
It might work in theory, but its a non starter in the timespan and met condtions where snowclearence is an issue. No runway is hard to keep open BA
wise in good condtions, it's the days with heavy snow that is.
Today, when we really need the snow removed, we have the sun below horizon, and snow is falling in heavy showers. Raising the temp in the runway would only dictate a change from sand to urea in the gritter. Still going to need hundres of man-hours working the sweeepers.
Now, high power warming, raising the temp to +10C with -35C in the air........ Now we're talking.
[Edited 2004-12-12 13:26:47]