[Nisgeis]

Right, just had a quick check of the functional diagram for the TDC to check my facts. There is a very subtle, but very important difference between the real TDC and the in game TDC.

The real TDC has the bearing input crank connected via an adder to the target course (relative tagret course is what the TDC refers to it as, but it's the same as AoB). The in game TDC does not. What this means is that when you adjust the bearing, the target course (AoB) also alters to match. We know from the other explanations about how to get the AoB by drawing it on the map, that the AoB is the angle between the target track and the bearing to your sub. If you can imagine the target moving up and down the target track (like its on a rail) then as the bearing changes, so does the AoB by the exact same amount.

For example, if a target is deads ahead of you at a bearing of 000, steaming a course relative to you of 090, then when the target was at a bearing of 315, the AoB was 45 and when the target will be at a bearing of 045, the AoB will be 135. So that's the maths behind it, the relationship between the AoB and the bearing is a simple addition/subtraction.

The target course is also connected to the range counter by an integrator, so changes in the target's range and course, due to its own movement are taken into account.

What does this mean? It means that with a real TDC, when you hold the bearing you are keeping the course the same and this means that the solution you have is always valid for the point where your scope's aiming wire intersects with the target's course (regardless of where the target is. The target's speed is fed into the gyro angle solver, so the torpedoes will be sent on their way to intersect with the target as long as your speed estimate is correct. You are effectively making the TDC simulate a constant bearing reducing range problem for the aiming point. You are basically on a collision course for your aiming point and the target moves accross the aiming point.

This is all quite confusing and is hard to visualise without a diagram, but the basic principle is that the stern has a different relative course than the bow, when seperately viewed. In game, as the TDC does not change the AoB with a change of bearing, then winding the bearing back will not work accurately, as you'll get a different course. This should only generate a small error however. It's easier to try to visualise this if you imagine an infinitely long target.

Sorry if none of this made any sense.