Originally Posted by
pitchtrim
Last time I checked if you take wings off the fuselage, it doesn't create lift and falls like a rock. Nor is the fuselage heated to prevent ice buildup, yet airplanes are flying around just fine in ice. How many years has the mighty 200 been flying without full type 4? Suddenly we need to create heavy work load in horrible weather conditions, destroy a bunch of apu's after they injest fluid, and pop everyone's ear drums in the process.
Your right in the case of most airliners, the fuselage does not provide lift. But with rear mounted engines, it does provide a great surface to accumulate ice that can then be injested into the engines.
I deiced last year, and if I remember correctly, but I may have it switched with the 700/900, every operator that flew into pit with 200's required type IV on the top of the fuselage as well as on the wings tail if they were getting IV at all. I do remember that it was different between the 200 vs 700/900, which I found odd, and then even airline to airline.
But this whole argument is sort of pointless. You don't get Type IV every single time, only if you need a holdover time longer than what type I can provide.
Originally Posted by
ClickClickBoom
Type 4 is designed to shear off the surfaces at aprox 100 kts, Type 1 just drips off. Type 4 is just Type 1 + cornstarch. Not much magic involved.
That is 100% false, about type IV...
Type four is thick compared to type I as it is straight Glycol where as type I is always a Glycol/water mix and the water content is based off of that day's temperature. We would watch the ratio for type one very closely, testing it every crew swap or as conditions changed. If it got out of spec, we would add glycol. If your worried about it getting into an intake, you should be more worried about type I.
And while type IV provides a holdover time, with the right conditions, it won't even make it to the shear point as certain precip will begin breaking it down.
Remember people, Glycol itself has no anti-deicing properties. Glycol is used because it is very very good at carrying and transferring heat. Type IV on the other hand forms a barrier between the snow/ice and surface and then slides off taking the containment with it.