A320 spoiler panel frost
 

Does anyone know why the spoiler panels alone are prone to developing hoar frost on the A320? The only idea I can come up with is that the thinner panels cool more quickly through radiative cooling, but equally the wing surface was well below freezing too and perfectly clean.

Hi Fursty Ferret,

Just a guess, but I imagine the surface of the spoiler panels dropped to a lower temperature than the wing skin (which is above the mass of warmer fuel and hence takes longer to cool). When the spoiler skin temperature was below the dew point, then frost formed, but the wing skin never cooled far enough.

The fact that those panels are composites (CFRPs) might be a -if not the- factor as well.