King Muppet:
You are absolutely right, and it seems many pilots actually missed that point.
Type I-fluids (de-iceing) are designed to leave the surfaces as soon as any force is applied to them, like accelleration, wind, etc.
Type II and IV-fluids (anti-iceing) are pretty much the same as Type I-fluids, except that they have added thickening-agents and other various substances to the fluid, to make it more resistant to precipitation, and to make it stick better to the surfaces, and thereby give a longer lasting protection.
Basicly, as the aircraft approaches 80 kts, the anti-iceing fluids will start to come off the surfaces, and by 100 kts, the fluids will have left the surfaces, leaving only traces behind. The remaining fludis on the surfaces will give no protection what so ever.
The reason for designing the fluid to separate is because the fluid will cause unwanted changes to the aerodynamics of the wings. As the airspeed increases, the surface-tension of the fluid will keep the fluid from beeing blown off, but it will however be moved towards the trailing edge of the wing and horisontal stabilizer, altering the shape of said surfaces at the same time. This is until the airspeed of 80-100 kts is reached, and the surface-tension finally gives in and the fluids come off.
For this reason, anti-iceing treatments is only applied to aircrafts with Vr higher than a minimum of 80 kts. Some airlines use 100 kts for this limit.
Many pilots are not aware of this, and i have refused to give anti-iceing treatments to aircrafts where the commander insists on Type II-fluid, and the aircraft have been a slow-moving turboprop or piston-powered model.
Sure, it's his call to make, but as long as he shows no sign of understanding the aerodynamics involved in his decision, he's not going anywhere.
Blackmail:
You too hit the nail straight on the head! It's sometimes scary seeing commanders making their decision on wether or not to de-ice.
"Ohh.. The plane next to us didn't de-ice, so neither will we..."
The plane next to you may have been hangered all night, while yours have been outside accumulating ice on the wings and horizontal stab....
I've seen it happen, and as luck would have it, they were ok... The high-wing turbprop took off with 1-2 mm's of ice on the entire wing and tail. The de-iceing personell had left a warning for the crew, but they never got the message...
Some pilots do have a severe lack of knowledge when it comes to operating in winter-conditions, and would rather rely on gut-feeling and previous luck, than following SOP for contaminated wings...
It's scary out there boys and girls, but as luck will have it, they usually make it....