TDC updating newbie question

[Pisces]

Originally Posted by BigWalleye

For a "normal" ( near 90 degrees) attack, the range does not matter. ...

Sorry, a 90 degree set up has nothing to do with range settings becoming meaningless. It is the gyro angle being 0 (or close to it) that makes the range setting become meaning less. If the torpedoes do not have to turn (gyro = 000), then the TDC does not have to account for the parallax angle that develops when the torpedo does need to turn and and sees the target from a different approach angle at the end of the turn.

As an aside: Parallax is the situation where you see a close object at a different direction (different things on the background horizon) than a person standing 10 meters or yards away. And is (part of) the means how your eyes perceive distance at close range. Your eye balls turn towards each other to aim at the object in focus. Your brain does the triangulation.

It might be that in this 90 degree setup you choose, by default, to wait until the target is almost in front of you. And therefore get the gyro-angle to be close to 0. But it isn't the differences in own course and target course that makes the difference in chances of hitting. Try firing at the target when your boat is aligned parallel to the target course and it comes to the bearing of 270 or 90. (which is also what the gyro angle will be close to) As you fire to your port or starboard side, you might get a hit. But it won't be the point on the hull that you aimed for at different distances. You will expect this to happen if the torpedoes move straight ahead out of the tubes. If the torpedoes need to turn, close distance makes it worse.

Ever wondered why torpedoes tend to miss when you fire too late or early? The target is on a bearing far away from dead ahead, and the distance is close. This enhances the correction that the torpedoes need to make for the parallax deviation. If the range is still from an older moment and thus further away, the torpedo is not properly aimed.