C172 contrails

[Kolibear]

A couple of weeks back, flying on a damp day, I was convinced that I could see a small, thin trail of vapour coming off of the outboard corner of the flaps. The flaps are permanently drooped to 6degrees so there is a sharp point to propogate avortex. It was only visible on the down-sun side of the aircraft, the other side being too bright to see if there was a trail coming off of the other flap.

I can only assume that as Genghis said earlier, the corect conditions had been met for small vortices to apear.