Constant Bearing Method, with TDC

[Rocks'n'Shoals]

Hello fellow captains,

I have newly subscribed, but have been eavesdropping as stowaway for a while now. I am actually an old hand in playing Silent Hunter. I have enjoyed them all: SH1, SH2, SH3 and SH4... Stock game in SH4, no mods yet.

I want to share the most accurate method for shooting torpedoes in SH4, American submarine, which I have come across so far. It is a constant bearing method which employs the TDC. Whenever I use it, and do everything right, I get sure hits, even with long-distance shots up to 4000 meters. I have also found it to work well for convoy surprise attacks. Last time I encountered a convoy, I got all 3 front row ships with my 6 bow torpedoes, they all sank...

Ok, here we go... I have included screenshots for clarification.

First thing to do when acquiring a new ship contact: Determining course and speed. I won't go into details here on how to do it, there are many well-documented methods plus it's easy when map contact updates are set to "on", but it has to be done with a high degree of accuracy for the constant bearing method to work out well.
Draw the enemy course line on the navigation map.

Second step: Choose your firing spot, somewhere near the target course line, wherever you like best. Go there, and stop the sub completely. We will stay here until after firing.

Third step: Choose the line of bearing for your attack. This is the constant bearing line which we will aim along later. Draw the constant bearing line on the nav map using the ruler. You get the distance from your sub to the target when it will be at the aiming point. This is not a critical measurement.



3000m - is he kidding....? (I am playing with metric units here.)

Fourth step: Use the protractor tool to get the exact AoB.



64 degrees starboard.

Fifth step: Now we need the angle between our heading and the constant bearing line for setting the periscope. Easy when you have a 360° Bearing Plotter, just read the scale on the constant bearing line. In the stock game, I don't have it, so I measure the absolute angle of the constant bearing line with the protractor tool.



113 degrees, add 180 for left (western) side -> 293 degrees.

OK, now let's input all the data into the TDC. The Position Keeper remains off, we set up for a static solution. Don't forget to confirm each step by pressing the red "Send to TDC" button with the white triangle on it:

Target speed...



Angle on Bow... (not easy to input exactly!)



Target range... Read it on the PK



OK, now set the periscope to the preselected constant bearing. I repeatedly press the "set heading to view" button for that. We won't turn because we don't move, but the chief executive will read you the absolute bearing you are looking at currently. I repeatedly try until it matches the absolute value of my constant bearing line - 293° in my case. Press the red triangle button on the TDC again to confirm it.



(Note that the PK will now display the data you did enter - for example the AoB.)

Don't touch the periscope after you have done this! Its vertical line is now our well-aimed firing reticle. We will wait until the juiciest parts of the enemy ship cross it, and fire exactly then!

For now, let's wait submerged at periscope depth, periscope lowered, well hidden and silent until the enemy is where we want him - no need to expose the periscope until just before firing... We are playing now a big, silent hole in the water, but a hole with a well-aimed high-precision gun...

Now is a good time to open the torpedo tubes, go to silent running (without moving), and ring the bell for battle stations.

The nav map with its sound bearing lines is a good indicator when to raise the scope for the firing procedure.



Up scope! Let the target steam into the firing reticle. Fire at will. I usually shoot two torpedoes, one into the foreship, one aft. Three torpedoes will do nicely for larger targets.



Oh, a small Engine-Aft - I didn't look earlier, set it all up using radar data only...



Both running straight and true. I love those Mk23's...



Really? At 3000 meters...?

Additional comment: For a convoy attack, I use the same procedure, and set up for an average distance. Using an AoB between 60° and 80° (depending on target speed), I can fire at two or three ships which are aligned in a row, furthest first, nearest last, to time the torpedo impacts near-simultaneous. Let them run into the firing reticle, one ship after another, they are all traveling at the same course and speed - unless previously alerted, which is when they go into wild zigs...

Happy shooting!