Quote:
Originally Posted by gmetzo
Hi , I know this is a post from like a decade ago , but could you possibly elaborate on how you are utilizing this card? Or if someone can point me to documents about it? I am not sure I understand how it functions.
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The chart is set up for firing a zero gyro angle shot (torpedo running straight ahead, to hit as the target crosses your bow).
This one is specifically for a torpedo running at 44 knots, and you'd need different charts for different speed torpedoes.
Across the top is the torpedo track angle (the angle between the target's course and the torpedo's course). Because the torpedo is running straight ahead, this is also the angle on the bow when the target is directly ahead of you, since the line of sight at this time would be the same as the torpedo track.
Down the side is the speed of the target in knots.
Each cell in the chart is the lead angle at firing time.
So, to fire a torpedo at a ship doing 1 knot on a course that is directly perpendicular to your course, you would aim your scope at 1.3 degrees (port or starboard, in the direction the ship is coming from), and when the ship crosses the center wire, you fire.
For a ship traveling 12 knots on a course that is 70 degrees off of yours (it is coming towards you slightly), the lead angle would be 13.2 degrees.
A 20 knot target crossing you at 140 degrees (headed away from you somewhat), the lead angle is 24.1 degrees.
In the situations described, G=0, so Ta and TTa would be the same. Because of the way the math works out, range is completely irrelevant.
For a little light reading:
https://maritime.org/doc/attack/index.php