Francisco De Almeida wrote:
The German manufacturers would rather have their customers release the =
tail ballast at +2=BAC. I suspect solar radiation is the reason why =
people can keep their water at lower air temperatures without =
immediately being awarded a split tailplane.
So if you have both outside temperatures below 2=BAC and no sunlight ... =
beware!

I've been assuming that solar heating is the reason that the tail
ballast doesn't end up freezing during these summer flights. At a few
degrees below 0C in shadow, it should still take something more than an
hour for a few liters of water to freeze to the extent that it would
cause structural damage. Lack of lift and cold toes would cause me to
seek warmer environs long before that point...