Originally Posted by
stendec
Wondering why the frost or ice is only on the spoiler panels.
It
may be that the thermal mass of the spoiler panels is less than that of the other wing components - the flaps are physically larger, and the wing skin is both better attached to the spars and may also be touched by wing fuel.
If so, then the spoilers will cold soak faster than the rest of the airframe, and perhaps reach a frost-forming temp first.
Another possibility is that the energy in the boundary layer has dropped as the flow moves aft, such that there is less kinetic heating of the surface on the after portions of the wing, and this just happens to be where the spoilers are.
Both effects might be present, too.