(ask) problem with enemy's course and precisely fire torpedo with sonar

[MKalafatas]

I nearly always use sonar without periscope or range info, once I've ID'd the target. Range is irrelevant if you fire from the beam (limited only by torpedo arming distance and max torpedo range). Ergo, I use only passive sonar. You need only know the target speed, course, and correct firing angle. (e.g., 7 knots translates to an 11-degree firing angle if you're perfectly on the beam, and use a 36-knot Mark X; 9 knots = 14-degree firing angle). When the sonar man calls out the bearing of the approaching target, and it reaches the firing angle, I shoot. Actually I generally shoot about 1 or 2 degrees in advance, depending on how large the target is and how many torpedo hits will destroy it.

If you wait the 8 seconds or so for the "torpedo in the water" call, that generally translates into about 2.5 or 3 degrees of target bearing, moving across your bow.

Using the stadimeter, my torpedo accuracy was around 50 percent. Using sonar only, it exceeds 75 percent.

One caveat: zig-zagging targets are very difficult to hit this way.

Edit: so it was YOU who sunk the Essex?????

[TorpX]

Originally Posted by MKalafatas

I nearly always use sonar without periscope or range info, once I've ID'd the target. Range is irrelevant if you fire from the beam (limited only by torpedo arming distance and max torpedo range). Ergo, I use only passive sonar. You need only know the target speed, course, and correct firing angle. ....

At the risk of coming off as onery, I feel I have to point out a few things here.

The "range is irrelevant" is often repeated, but is really misunderstood. It is true that you can compute the lead angle for a firing solution, knowing the speed, track angle and bearing, without knowing the range, but that does not mean the range is irrelevant. (Also, it has nothing to do with the sub being on the "beam". The range dropping out of the equation for the lead angle holds only for a zero-gyro angle solution, whatever the positions of target and sub.) The firing solution for a 4,000 yd. shot may have the same angles and speeds, as a solution for a 2,000 yd. shot, but they are not the same. A small error in the data that would get you hits at 2,000 yds., would likely produce misses at 4,000 yds.

The thing often glossed over is the question of how would you obtain the speed or course without knowing the range? Speed might be estimated by observing the bow wave or by 'seaman's eye', but this would require visual observation anyway. Timing by wire also requires visual observation. The only other way I can think of that would not require any range info, is to use propeller counts. I think in practice RL captains relied mainly on calculations of distance/time (i.e. plotting). Another thing is that it would be almost impossible to determine the target's course without either knowing the range at several points, or accurately observing the AoB. This brings you back to visual (or radar) observations again.

Only a very few "sonar-only" attacks were made by US submarines. As far as I know, none were successful.

[Daniel Prates]

Originally Posted by TorpX

At the risk of coming off as onery, I feel I have to point out a few things here.

The "range is irrelevant" is often repeated, but is really misunderstood. It is true that you can compute the lead angle for a firing solution, knowing the speed, track angle and bearing, without knowing the range, but that does not mean the range is irrelevant. (Also, it has nothing to do with the sub being on the "beam". The range dropping out of the equation for the lead angle holds only for a zero-gyro angle solution, whatever the positions of target and sub.) The firing solution for a 4,000 yd. shot may have the same angles and speeds, as a solution for a 2,000 yd. shot, but they are not the same. A small error in the data that would get you hits at 2,000 yds., would likely produce misses at 4,000 yds.

The thing often glossed over is the question of how would you obtain the speed or course without knowing the range? Speed might be estimated by observing the bow wave or by 'seaman's eye', but this would require visual observation anyway. Timing by wire also requires visual observation. The only other way I can think of that would not require any range info, is to use propeller counts. I think in practice RL captains relied mainly on calculations of distance/time (i.e. plotting). Another thing is that it would be almost impossible to determine the target's course without either knowing the range at several points, or accurately observing the AoB. This brings you back to visual (or radar) observations again.

Only a very few "sonar-only" attacks were made by US submarines. As far as I know, none were successful.

Ha! My point exactely.

Another key issue to consider is that you should always try to fire from as close as possible. All margins of error decrese as you near in (except for your personal safety margins, but that is another issue). If we are talking about a lonely merchant, it is fairly easy to lurk ahead of him and wait till he is less then 2000, maybr 1500 meters away. And in that situation, a couple of statimeter readings are all you need for a "good-enough" range (and speed!) estimate.

[MKalafatas]

Originally Posted by TorpX

At the risk of coming off as onery, I feel I have to point out a few things here.

The "range is irrelevant" is often repeated, but is really misunderstood. It is true that you can compute the lead angle for a firing solution, knowing the speed, track angle and bearing, without knowing the range, but that does not mean the range is irrelevant. (Also, it has nothing to do with the sub being on the "beam". The range dropping out of the equation for the lead angle holds only for a zero-gyro angle solution, whatever the positions of target and sub.) The firing solution for a 4,000 yd. shot may have the same angles and speeds, as a solution for a 2,000 yd. shot, but they are not the same. A small error in the data that would get you hits at 2,000 yds., would likely produce misses at 4,000 yds.

The thing often glossed over is the question of how would you obtain the speed or course without knowing the range? Speed might be estimated by observing the bow wave or by 'seaman's eye', but this would require visual observation anyway. Timing by wire also requires visual observation. The only other way I can think of that would not require any range info, is to use propeller counts. I think in practice RL captains relied mainly on calculations of distance/time (i.e. plotting). Another thing is that it would be almost impossible to determine the target's course without either knowing the range at several points, or accurately observing the AoB. This brings you back to visual (or radar) observations again.

Only a very few "sonar-only" attacks were made by US submarines. As far as I know, none were successful.

Good post. Thank you.

[Rockin Robbins]

The width of the sonar detection in the game is always the same. You can find the outside on both sides and figure out the perfect bearing every time as the detection range is exactly 10º wide.

In real life that detection range is wider and variable. That means that where our in-game sonar bearing is accurate to plus or minus 1º, you're talking three or five degrees in real life. That makes all the difference in targeting accuracy.

It's also interesting that even though the pre-war official attack method was sonar only, I've never seen a description of their procedure. I'd love to see how their procedures differed from WernerSobe's or my techniques. It would be fun to use their exact method.

[TorpX]

It's also interesting that even though the pre-war official attack method was sonar only, I've never seen a description of their procedure. I'd love to see how their procedures differed from WernerSobe's or my techniques. It would be fun to use their exact method.

I haven't seen one either.

I find it interesting that eventhough it was "accepted doctrine", very few sonar-only attacks were made. Apparently, most skippers ditched the idea right away. But like you say, it would be interesting to try and do that way.

[Rockin Robbins]

That's what is most interesting. We're to believe that sonar only was "accepted doctrine" based on what? If everyone was expected to do it, the instructions should be easy to find. After all the Submarine Torpedo Fire Control Manual tells intricate details about every other known attack method, allowing us to perform them with great fidelity to the original submarines.

But there is not one word of information about attacking with sonar only. If it were a valid attack method that did not work, they would likely have included it for future reference and possible refinement into a technique that DID work. But instead we have not one word of reference to this "standard accepted doctrine" in a book whose purpose was to train sub officers in "standard accepted doctrine."

It seems VERY unlikely to me that a universal doctrine would escape all notice in the standard reference on submarine tactics. They would at least have mentioned and outlined the technique while explaining that visual firing methods have proved much superior.

So something doesn't add up here. There is a disconnect from what we have been told to the actual training materials of the time. It's probably useless after 60 years to speculate why this is the case.

[Daniel Prates]

Pure-sonar methods seem to be taking a hell of a beating...