well i did heard about the trophy. Does China have anything like this kind of active defence??
Nothing I know of. Perhaps you ask that question in the type 98 thread in the land warfare forum, since I think it's quiet related to that topic.
on another question, i was wondering about the external fuel tanks on jet fighters. Does it consume all of the external tank first first and drop it one by one or wait all of them to be empty and drop it
Probably depends on the situation. If there's no need to drop, they will bring them back home. If you drop them anyway, it just makes sense to drop them as early as possible. Since every single tank is a source of additional drag and weight.
If you have i.e. one tank under each wing, I think the jet consumes the fuel from both of them simoultaniously to avoid assymetric weight dispersal. Hence both could be droped at the same time.
Due to the weight, those tanks limit the max G-limit of a jet. If you come into a situation where high maneuverability is needed (A-A fight, avoid missiles) your going to drop all tanks at once (no matter how much fuel is left) and also heavy bombs, if you have those, to safe the jet.
What I understand is, passive sonar has longer range but less accuracy, so you have to measure sevral times to get an accurate location of enemy. While active sonar is more accurate but has less range. Moreover, it's possible that the enemy vessel is out of the range of your active sonar but within his range of passive sonar. So when you open your active sonar you will find nothing but the enemy will know your existance.
Basicly, you're right. There are a lot of factors to consider wich make the actual task in combat much more difficult of course. But I'm no expert on that.
Regarding range of passive sonar. It's difficult to actually speak of a range here.
I.e. lets say there is a sub 5000ft (random figure) away from your own. It may be that quiet that you cannot "hear" it with your passive sonar. If you'd use your active sonar and would point into the right direction, you might be able to hear the return signal. That would alert your opponent as well. But you have not only bearing, but also the range. (Such a hit would be pure luck)
However, no sane submariner will ever sweep the ocaen with active sonar in the hope to find another sub.
Besides, I think subs can be covered with some kind of rubber material on the outside to (partly) absorb active soner signals.