Firing blind

[voss]

I'm in the process of finishing my first patrol. A couple of times now, I have been in the position of sinking, or trying to sink, a ship in the pitch black of a stormy Nordsee night. I'm still hoping that the one ship that I sunk was a valid target because I couldn't make out the flag even in the flames of the sinking wreck. In both cases, these ships were "radio contacts" that popped up on my navigation map (I'm playing at near full realism, minus only the automatic map notifications). I am assuming that the reason these come in as radio contacts is because they are British ships and ready for sinking. Of course, I could be assuming my way out of a brilliant naval career. What is the scoop on the radion contacts? Ar they always valid targets? Thanks, in advance, for any advice.