Let's start with that one and then we can move on to airplanes at 15,000 feet and climbing. How does the sub know where the helicopter is so it can shoot the missile at it?
Why does the 'sub' have to know 'where' the helicopter is ? All the sub has to do is launch it. The missile (presumably) contains guidance and homing abilities and can 'find' the target itself. This type of 'missile' has been mentioned and discussed throughout the posts on this thread.