The convergence problem

[Hitman]

I have opened this thread as a continuation of the discussion initiated in the "How do you shoot your convoys", as I did not want to hijack it

I thought the convergence problem would be of interest for anyone doing manual targeting, so here goes a brief explanation:

When you calculate your firing solutions, you do it from either scope or UZO, but those instruments are not above the torpedo but instead some 35 metres behind, in the conning tower. Thus, if you fail in determining the distance to the target, you could have problems with angled shots, the more noticeable when the Gyro angles are high. In the following image you can see and understand where the problem is: Ship A and sihp B have exactly the same bearing from the periscope/uzo, however ship A is closer than ship B. Thus, if you miscalculated the distance target, the convergence between the bearing line (green) and the torpedo trajectory will produce itself in the wrong place. In ship A distance is correct, and the torpedo run intercepts the bearing to target (Line of sight) exactly where the target is. That's an impact! However, in case B a large error in distance coupled with a large Gyro Angle will cause the torpedo to miss the target astern, even if AOB and speed were correctly calculated.



Thus, keep this in mind:

-The larger the distance to target, the more likely a convergence error
-The worse the distance to target estimating, the bigger the convergence error
-The larger the Gyro Angle, the more likely a convergence error will have big effects
-The TDC applies the proper convergence correction (Try this: Go to F6 screen and with stationary submarine, set manually your target as 90º left or right of you, speed zero. The green line will converge with the line of sight from your scope at the distance to target you did input. Play a bit with the distance dial and you will see what I mean)

Hope it helps

EDIT:

You can check this in your TDC (F6) screen:

Set the TDC to manual input. Move the bearing to target dial to 90º left , leave AOB and speed at zero. That would represent a target being stationary left of your submarine, periscope/uzo bearing 270º (90º red side). Note that the green line for the torpedo is curved, making the torpedo run match the 270º bearing from your boat exactly at the distance you told the TDC that the target is. Play a bit with the distance dial and you will understand what I mean.