[snakedocpl]

Hi Gentlemen,

Originally Posted by Sniper297

I've used both systems, I currently have a German ATO career and a US Pacific career active in SH4, and even though I don't use the PK much I still find the TDC easier to use simply because the "own ship" and "target" dials one above the other makes it easier to visualize the situational awareness "picture" for the approach. I have used the "angle off" method where you estimate the intercept angle, set the fish for a zero gyro angle, then offset the scope 10 to 15 degrees and fire when the target hits the crosshairs, but that's usually reserved for the S-class which wasn't supposed to have a TDC in real life.

If you are sharing with us your experience based only on feeling from SH (and not on a base of real documentation), your opinion is quite irrelevant. Until now, there is no submarine sim with correctly implemented torpedo fire control computer (neither TDC nor TVRe).

Originally Posted by Sniper297

The TDC had the same capability of shooting multiple targets and/or spreading by shifting crosshairs, there was a button on both periscopes and the TBT to send a new bearing to the TDC - if the speed and course of the target(s) didn't change all you needed was a new bearing.

No, TDC had no capability of shooting multiple targets and/or spreading by shifting crosshairs (if we are talking about real TDC Mark 3). The reason: there was no connection between target bearing transmitters (at periscopes or TBT) and TDC (or more strictly with Position Keeper).

Source document: https://maritime.org/doc/fleetsub/elect/chap14.htm#14C

At TDC were only target bearing receivers, which were observed by TDC operator and their value was compared with the target bearing value generated by Position Keeper. If these values matched, the target data (course, range and speed) entered to the Position Keeper were correct, if not - the target data has to be adjusted.

Here you have the functional diagrams of Position Keeper and Angle Solver and there are not electrical inputs for target bearings.
https://maritime.org/doc/tdc/pg068a.htm
https://maritime.org/doc/tdc/pg086a.htm

BTW, the only values electrically inputted to TDC were own speed and own course.

So you could train the scope and TBT and it does not influence the solution at all.

Similarly, the TDC did not calculated the spread angle. The spread angle had to be calculated by human and entered manually to the Angle Solver as so called Offset Angle. The Offset Angle modified the gyro angle entered to the torpedoes, so the Offset Angle handle had to be trained after launching each torpedo in salvo.

Originally Posted by Sniper297

And the TDC had enough sense to fire at where the target would be rather than where it is at the moment the button was clicked, that's lead angle. I agree that the actual lead angle is nice to know if for no other reason than a double check on the accuracy of the TDC solution, but I'm sure there was someone on the plotting team responsible for checking that. Many skippers had someone on the attack team standing by with a "banjo" and Is/Was just in case, especially early in the war when the TDC reliability was still unknown.

As I explained above, there was no button. TDC philosophy was to have ability to fire without periscope. I mean, if you entered the correct values to the Position Keeper, it continually calculated the correct relative position of the sub and target. Based on the output from Position Keeper, Angle Solver calculated continually the correct gyro angle, so you can shoot any time, without seeing the target.
The periscope target observation were done to check the accuracy of the Position Keeper solution. The TBT/Periscope operator shout "Bearing Mark!" or pushed the button, and the TDC operator compared observed target bearing with target bearing generated by Position Keeper. If target was at position calculated by Position Keeper, everything was ok, if not, target data has to be adjusted. It was iterative process.

Originally Posted by Sniper297

I don't know how you figure the TDC didn't have lead angle capability, target speed, relative bearing, and AOB equals lead angle - which was automatically updated in the torpedo gyrocompass. Put the crosshairs on the target, hit the button to send the latest bearing to the TDC, which sets the gyro angle for the correct lead angle, and shoot. Don't even need to know the lead angle, TDC sets that automatically.

Most of misleading information were corrected above. One more: torpedoes were not fitted with gyrocompass (which is devices based on fast-spinning disc and the rotation of the Earth, using the effect of gyroscopic precession, used for finding true north), but with gyroscope (device based on fast-spinning disc, used for determining fixed direction in space).

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Regards
Maciek