Ah, the gold standard for terminology when talking about submarine attack targeting. If you wonder where the words we use come from, look no further than there. When we talk about a constant bearing attack, don't assume what it is, look it up there. That is why I refer to the Dick O'Kane attack method having a longitudinal spread. Authentic language ensures communication is taking place. This site is a must see!

As no one has come back with anything that needs changing, the PDF can now be downloaded from:

http://files.filefront.com/TSAC+v21p.../fileinfo.html

Get your torpedo run time from the attack map (it's at the end of the greeny black torpedo run line). I've no idea where people are getting the target lengths from. All other instructions are included in the PDF, with three examples, showing how to use it.

Edit: V2.1 added instead of V2, as there was a slight error.

I hope I will have this weekend the in-game version done, and will send it to Nisgeis for approvement :up:

Thank you both. This is a large void in our abilities that you have cured, plus the chart is useful for other things too, as we found out while formulating the John P Cromwell technique. I think I'll use it more than I do the nomograph and I know I'll do a lot more conventional targeting now that I can do divergent spreads with confidence.

Nisgeis, Hitman, great job!

Ops... sorry i wanted to reply to another thread! too many open windows!

No you don't! You really want to download this thing and put it to use. It is really great!

I am coming in a little late
 

I just studied the Torpedo Spread Angle Calculator thread. Nisgeis, congratulations on a masterpiece. My son has not seen it yet and will be beside himself when he reads it.

Has it been put into a mod? Can it be pasted on the attack map? If so, are there easy to following structions?

Many of the posts in the thread are from individuals on the cutting edge of this game's technology, and it is one of the most interesting running commentaries I have come accross. I am wondering how the calculator will work when I used manual targeting. RFB has a mission called the Dick O'Kane, where it is a perfect place to practice it. I can save the mission right before I set the torpedo spread angle, so I can replay it quickly and efficiently to test it.

I have one question about the pdf. What is the torpedo track angle? Is it the angle that the arrow points to on the image representing my boat on the TBT? I think it is, but I am not sure.

part of answer to my post
 

The torpedo track angle is found by pointing the cursor at the arrow on the target on the TBT, not the by pointing the cursor at the arrow at your own boat.

If the torpedo spread angle calculator has been modded into the game please advise by leaving a reply.

it's already in rfb i think

Hitman was working on that and it appears to have been dropped. He was going to put it on the attack map and we must bug him about that because I'd love to see it in operation.

Nope. The torpedo track angle is the angle the torpedo makes with the target, with zero at the bow and 180 at the stern of the target. It's called the track angle because it is the angle the torpedo track makes with the target track. Here's an illustration from the Submarine Torpedo Fire Control Manual:

http://hnsa.org/doc/attack/img/pg01-12a.jpg

I guess that's about all the information I can supply based on the diagram, except that if you draw a line from the periscope to the target impact point, notice that it will be a different angle than the gyro angle. That is the parallax we've been talking about, due to the length of the sub and the torpedo reach before it begins its turn toward the target. Also notice the Angle on the Bow. The torpedo track angle is just the angle on the bow of the torpedo itself at the moment of impact!

How do you you compensate for inhernet TDC errors?
 

RR, thanks for the information about the track angle. Here is a follow-up to our conversation yesterday.

How do you compensate for inherent TDC problems?

If the target's speed input into the stadimeter is 7.5 kts., the TDC interprets its speed as either 7 kts or 8 kts, as it rounds the target speed to the nearest knot. This results in a speed differential of 1/2 kt. Assume range, aspect ratio and AoB are correct. Because of the 1/2 kt. speed differential, the gyro angle for the torpedoes estblished by the TDC is incorrect.

If the TDC interprets the target's speed as 8 kts., it will set the gyro angle for torpedoes based on the target proceeding at that speed. But the target is not proceeding at that speed! Its actual speed is 7.5 kts., 1/2 kt. slower than the TDC's calculated speed. For example, if a target is proceeding from left to right, the torpedoes will run ahead of its bow (i.e. to the right), because the TDC assumes and calculates the torpedoes' gyro angle (and target's position at the point of contact) based upon a target's assumed speed of 8 kts. The TDC sets the gyro angle of the torpedoes to intercept the target based upon that speed. The torpedoes run ahead of the target's bow because the target is running at 7.5 kts, which is 1/2 kt. slower than the TDC's calculated speed of 8 kts. In reality (if that description is proper for a game played on a computer) the target's actual positon at projected point of torpedo intercept is behind the position calculated by the TDC because it is moving at a slower speed than the TDC data utilizes. This is not caused by an error on the part of the captain, who input the correct speed of 7.5 kts. into the stadimeter. It is the result of the TDC rounding the input speed of 7.5 kts to 8 kts. In my two tests, a total of eight torpedoes that were fired in salvos in two separate attacks in RFB ran ahead of the target's bow, missing their targets by a short distance.

Conversely, if the TDC interprets the target's speed of 7.5 kts. as 7 kts., just the opposite occurs. The TDC sets the gyro angle based upon a speed of 7 kts. But the target is actually going 1/2 kt. faster (7.5 kts) than the TDC's calculated speed (7 kts.). For example, if a target is proceeding from left to right, the torpedoes will run behind its stern (i.e. to the left), because the TDC assumes and calculates the torpedoes' gyro angle based upon a target speed of 7 kts. (1/2 kt. slower than its actual speed) and sets the gyro angle of the torpedoes to intercept the target based upon that speed. The torpedoes run to the left because the target's speed is 7.5 kts., which is faster than the TDC calculated speed of 7 kts. In contrast to the example in the preceding paragraph, the target's actual positon at point of impact is ahead of where where the TDC calculates its position because it is moving at a faster speed than the TDC data assumes. This is exactly what occurred with four torpedoes that were fired in a salvo in a campaign mission. One of the four torpedoes made contact near the target's stern for reasons explained below.

How to adjust or compensate for the TDC data error?

It seems to me the solution lies with setting the spread angle on the torpedoes, or by leading the target when firing. As to the former solution, presumably setting the spread angle for the torpedoes is a technique that can be used to adjust for the speed differential caused by data input errors inherent in the TDC. However, the onboard ship manual does not list the lengths of ships, which is an element of the torpedo tracking angle calculation used for setting torpedo spread angles. Also, even if the torpedo tracking angle is accurately set to ensure a proper spread angle for the torpedoes, the torpedo tracking angle calculation does not assist in overcoming the distance differential resulting from the discrepancy between a target's actual speed and the speed recorded in the TDC, which, as noted, can be up to 1/2 kt since the TDC rounds speed to the nearet knot. If the speed differential results in the torpedoes running ahead or behind the middle of the target or the area of the target where the TDC projects impact, it can (and in my examples, did) result in shots missing the targets.

If you try decrease or increase the lead angle when firing, I am not sure how to do it, and secondly, whether it is possible with manual targeting.

In each of the three attacks described above, I tried adjusting the torpedo spread angle. Since each target was heading from left to right, I set the torpedo spread angle to the right to increase the odds of hitting the target. Here is what happened.

1. The first two attacks occurred when the targets' speeds were 7.5 kts. and the TDC calculated their speeds at 8 kts. The targets' speeds were each 1/2 kt. slower than the TDC calculated. The torpedo spread angle should have been set to the left to compensate for the slower speed of of the target. Setting the spread angle to the right was a mistake and increased the liklihood the shots would miss to the right, which they did.

2. The third attack occurred where the target's speed was 7.5 kts. and the TDC calculated target speed at 7.0 kts. The target's speed was 1/2 kt. faster than the speed used in the TDC calculation. The torpedo spread angle was to the right. One torpedo made contact near the target's stern, and the other three missed to the left. The torpedo spread angle was insufficient to overcome the 1/2 kt. discrepancy between the actual and calculated speed for three of the four torpedoes, but I was guessing at the spread angle.

Is there any solution to this TDC generated problem short of guessing at the appropriate spread angle for the torpedoes?

If this post is hard to understand, note that I had a hell of a time writing it. (Note: The problem generated by the TDC was pointed out to me by Rockin Robbins.)