Hoar frost vs De-Ice fluid...
 

Can someone shed light on the following!
I was recently flying as a pax flight seated over the wing area of an A330...
We had a small amount of hoar frost on the upper wing surfaces, the aircraft was de-iced.
OK. Good!
I observe that, lets just say the hoar frost is about 1+mm thick...
Having removed this... I then watch the same 1 + mm thickness?? of type 2 de-ice fluid on the upper surface of an A330 wing during the T/O roll. It did not 'shear' off at rotation. Rather it flowed off at boundary layer velocity continuously from T/O till for at least another 5 - 10 mins...
So. What is the difference aerodynamically between 1+mm of frost vs 1+mm of thickened de ice fluid in affecting CLmax???
?????

deicing fluid is generally 'smooth' which helps a lot

the OEM has likely demonstrated that the fluid had no practical effect on aerodynamics; I doubt they could do the same for rough ice.