Why? I'm just curious what the relative advantages and disadvantages are. It seems TKS would have the advantage of the fluid running back and helping to clear "non-protected" surfaces, but the major disadvantage of having to refill the fluid and the potential for running out of fluid.
I don't know much of anything about bleed air.
I've flown aircraft with the three different anti-icing/deicing systems so I'll try to give you some advantages and disadvantages. Keep in mind that my experience has not been with deicing systems in very small airplanes, although they are not huge airplanes either. Below is the order in which I was exposed to these systems. I'm not sure whether or not having seen one system before the other one creates a preference for the more familiar one.
Boots (King Air): Since it's a deicing system you need to wait until ice actually builds up on the boots before cycling them. Some residual ice is usually left adhering to the boots. This can be reduced by treating the boots with certain products. It's also important that they are well maintained since rubber tends to deteriorate and get holes, etc. I'm not an aeronautical engineer but I'm not sure how well boots would work on airplanes with critical airfoil and leading edge designs because they don't join to the wing as smoothly as with other systems.
Bleed Air (Lear 35): Bleed air is an anti-icing system which uses hot air from the engines to heat the wings, stab and nacelle inlets. The airplane has to have enough excess thrust to use this method because siphoning off bleed air for anti-icing robs it from the engine causing a decrease in performance. Bleed air is very reliable and you don't need to refill it. Even though it's designed as an anti-icing system it will remove ice already on the wing if you don't turn it on in time. This is not the ideal situation, however, because as it melts off it could get ingested by the engines.
TKS (Hawker 800): TKS is also an anti-icing system, which means that you need to get it turned on at least a couple minutes before you enter icing conditions so that the leading edges of the wings are coated. Sometimes this is difficult to predict. This is very important because if ice starts to cover the holes you are pretty much out of luck. The fluid, at least in this airplane, is not heated so it won't melt ice. You also have to prime the system on the ground before every flight and also at other specified times if you think ice will be encountered. It's a messy system and requires a lot of attention by maintenance to keep it working properly. The leading edges need to be kept clean but sometimes just wiping them down aggravates the condition by pushing debris into the little holes. Unlike bleed air and boots (which are actually also run off bleed air), you can run out of TKS if you have not been careful about refilling it. As Kent mentioned, I guess one advantage of TKS is that if it is on long enough it can run back a little ways past the leading edges and protect those areas. However I don't think it will remove ice that is already there, nor will it come even close to covering the whole wing area.
These are just my own observations off the top of my head. I'm sure people can think of other plusses and minuses.
I think it depends on the type of fluid -- Type I is a low viscosity, highly effective deicing fluid, but it would blow off in the breeze, but can be pumped out to deice the wing.
Type II, III, and IV anti-icing fluids, which have a higher viscosity, do not deice, they just prevent ice from forming in the first place, so they would be useless in a TKS system.
TKS may be similar but it's not the same as the Type I, II, III and IV fluids used for ground deicing/anti-icing. It only comes in one viscosity.
