4 Bearing method, useless in combat?

[barker262]

Dear Subsim,

My first ever post on your forum , which I might add has taught me so much in a short space of time; I thank you for that. But to the four bearing method, with a little playing background first...

I love sims, flight mainly, but anything that gives me an atmosphere, a sense of 'being there'. I have owned silent hunter 3 for years, but never played it, fear of failure perhaps, but I've loved the genre since Aces of the deep which I played to death.

I finally got the urge to get into the sim, started firing topedos about the place and not hitting a thing. I read about ranging and setting TDC, mastered that (well proficient anyway). I read with interest the articles about hydrophone only attacks, the 4 bearing method, got my first hydrophone only torpedo hit last night and got that warm glow of accomplishment .

Then 1939 was over and the convoys appeared, now time to use the skills gained. I found a convoy in the never ending rain off the coast of england, but never saw a single ship, so I would have thought that this was the perfect opportunity to use the method. What the hell?! Can't track a ship, hydrophone wont stay focused on one target. Can't move submerged as the escorts detect your noise immediately. I even threw every thing learned out the window and charged into the convoy.. but I'll leave that for my next post.

So Kaleun, what do you think?

P.S. Playing the game with GWX mod on 87% realism, (external camera and events).

[Shkval]

Heh heh , hydrophone is useless in convoy attacks, except if you are firing large salvo at long range, (shotgun approach) and if you hit something - you hit it... you can try to calculate the bearing to the center of a convoy yourself... but it's imprecise... bottom line, transfer the four bearing method to scope... choose one ship and take his bearings with scope every 5 minutes or so...until you get the course... don't try to get fourth (predicted) bearing, and fifth (triangulation one for getting the speed and range)... the course is all you need... place yourself to "T" course... to get the speed use cross-hair and length of the ship + time on stopwatch formula... IF they all keep their course and speed... you aimed at one - you aimed them all. Fire at the furthest one first...

[Mittelwaechter]

'Hydrophone Only' is not for your 'combat' situation, but for single contacts (unidentified) in heavy fog or with destroyed periscopes. You may even successfully attack a submarine at periscope depth...

[BigWalleye]

This Four-Bearing Method is useful for detection and approach, not for engagement. It is used to determine range, course, and speed with precision adequate to position the sub for a visual firing setup.

USN doctrine in the 1930's did suggest hydrophone-only engagement of capital ships in task force strength. USN believed that ASW defense might prevent the sub from reaching a firing position using periscope observation. Once the US entered the war, this was quickly proved wrong on two counts: First, IJN ASW defense was not that strong. And second, submerged firing based on hydrophone contact alone was so inaccurate as to be a waste of torpedoes. IIRC, there was never a EDIT: only one successful hydrophone-only attack made by any submarine of any nation during the war.

Fnally, while this was the pre-war doctrine of the USN, it was never shared AFAIK by the KM. The KM's most favored tactic was a night surface engagement, and hydrophone-only attack was never encouraged. I don't know that it was ever even tried by a German sub.

Use the Four-Bearing Method to set up your approach. The hydrophone is effective at 30+ km, generally farther than visual range in the ATO. Derive your firing solution from visual contacts at closer range. That is how it was done historically.

[maillemaker]

The imprecision of the hydrophone combined with the slowness of moving about the stations trying to set up a hydrophone shot would seem to me to be a very risky torpedo shot. You would probably miss.

I have taken to playing 100% realism with every single option on maximum difficulty. This means no map updates. Everything has to be done by the player sensing the tactical situation.

I find that I have adopted a much more "run and gun" approach to fighting, and I believe that it is probably somewhat realistic to the way it was probably actually done. Historically they may have had a somewhat easier time in estimations due to multiple people working the solution problem and also they had a much better sense of depth perception and a sense of bearing and distance than we can get from a computer screen.

But I find that nearly everything about setting up an attack approach is an estimate. And in that regard, it's probably fairly realistic.

About the only thing I can know with any real precision is the bearing to target based on visual observation. I then eyeball the target to get an estimate to the Angle on the Bow, and then I can figure out in my head what the target's heading is relative to my own heading.

I drive my boat to a 90 degree intercept. I only very rarely attempt non-90 degree attacks. It's just too hard to estimate a good AoB.

Likewise I have taken to estimating target speed. Unless I have been given a radio contact with an exact convoy speed, I usually guess 7 knots for target speed. This is what most merchants sail at. Sometimes they are a little faster, sometimes a little slower. I close to within 1000-500 meters and fire close to the center of the ship. Usually this results in a hit. However, sometimes I incorrectly estimate the target speed and miss.

The days of aiming torpedoes for specific areas of a target are over on 100% realism.

Steve

[flag4]

Originally Posted by maillemaker

The imprecision of the hydrophone combined with the slowness of moving about the stations trying to set up a hydrophone shot would seem to me to be a very risky torpedo shot. You would probably miss.

I have taken to playing 100% realism with every single option on maximum difficulty. This means no map updates. Everything has to be done by the player sensing the tactical situation.

I find that I have adopted a much more "run and gun" approach to fighting, and I believe that it is probably somewhat realistic to the way it was probably actually done. Historically they may have had a somewhat easier time in estimations due to multiple people working the solution problem and also they had a much better sense of depth perception and a sense of bearing and distance than we can get from a computer screen.

But I find that nearly everything about setting up an attack approach is an estimate. And in that regard, it's probably fairly realistic.

About the only thing I can know with any real precision is the bearing to target based on visual observation. I then eyeball the target to get an estimate to the Angle on the Bow, and then I can figure out in my head what the target's heading is relative to my own heading.

I drive my boat to a 90 degree intercept. I only very rarely attempt non-90 degree attacks. It's just too hard to estimate a good AoB.

Likewise I have taken to estimating target speed. Unless I have been given a radio contact with an exact convoy speed, I usually guess 7 knots for target speed. This is what most merchants sail at. Sometimes they are a little faster, sometimes a little slower. I close to within 1000-500 meters and fire close to the center of the ship. Usually this results in a hit. However, sometimes I incorrectly estimate the target speed and miss.

The days of aiming torpedoes for specific areas of a target are over on 100% realism.

Steve

that's really cool
...what we need now is your tutorial

are you submerged or surfaced - even at that distance you can be spotted - how do you carry on in bad weather?

[maillemaker]

In bad weather I have made pursuits by hydrophone - dive to periscope depth and use hydrophone to get a bearing, then surface and drive hard for 10-20 minutes and then dive and listen, repeat until you get a visual. Usually you can stalk around them at extreme visual distance without getting caught. This is risky once they start carrying guns because at 1000 meters they will tear you up.

My attack approaches are relatively simple. I believe there was a historical uboat captain who did similar 90 degree attacks almost exclusively.

The first thing is to make visual contact with the target(s). Your Watch Officer will be able to provide you with an exact range and bearing, unless you have installed a mod to reduce the range accuracy. Plot this point on your navigation map.

Next you will have to eyeball the target to estimate the Angle on the Bow, and thus the target heading. Draw a line on your map from the point of the target along its estimated heading.

Now you have to drive your boat to an intercept position such that you will be 90 degrees to the target when it passes in front of you. If you are at extreme range (10,000 meters or more) and there are no escorts with radar you can drive your intercept on the surface. You may have to drive away from the contact and do an "end around" maneuver to get ahead of them.

Once you are ahead of your target and are driving your boat on a course perpendicular (90 degrees) to the target, drive until you regain visual contact. Dive before you are spotted or the target will start zig-zagging making your job more difficult.

Proceed submerged until you are within 1000 meters of the target course. You will need to make periscope observations frequently to make sure you are on the correct course and that you are closing with the target fast enough to make the shot. Ideally you want to be within 1000 meters when you fire - I prefer 700-500 meters ideally especially for lone targets.

While you are waiting for the target to cross your bow, go to your TDC screen (F6) and turn on the TDC. You'll set up for a 90 degree shot. It's easy.

Set the Angle on the Bow to 90 degrees starboard or port. Remember, this is from the target's perspective. If you are on the starboard (right) side of the target, then you want to set the AoB to 90 degrees starboard.

Next dial up the target speed. You can infer the target speed by watching it carefully and by noting the size of the bow wake. Like I said, I usually guess 7 knots. It is possible to do a "fixed wire" method of timing how long it takes the ship to travel from stem to stern across your non-moving periscope vertical reticule, but to do this you need a positive ID of the ship from the ID book to determine the ship's length. With GWX gold there are so many ships by the time you thumbed through the whole book and found it the war would be over. However, if you know the ship's length, and you can time how long it takes it to travel past your reticule, you can get a fairly accurate speed using this formula:

speed in knots = length in meters / time in seconds * 1.94

In order to get an accurate time either your sub needs to be stopped or you need to be driving directly at it making your speed irrelevant.

With map contacts on it is trivial to place a mark on the target on the map, wait 3:15 seconds, then make another mark and draw a line beween the marks. That gives you the speed in knots.

Like I said, I find it easier to estimate speed now.

So, input the speed into the TDC.

Center your scope on 0 degrees, and toggle the TDC. Now move your scope towards the target. At about 5-10 degrees from zero (depending on the speed of your torpedo setting) the gyroangle will hit zero. This is where you need to aim your periscope regardless of distance to target. That is the nice thing about the 90 degree shot - distance to target is irrelevant. There is no need to set the distance in the TDC unless you want semi-accurate stopwatch time-to-target estimations. Since I usually shoot at 500-1000 meters I leave it at the default 500 meters. If something doesn't go boom shortly after the stopwatch passes the red line it's time to consider what you are going to do next.

Now you just wait for the ship to cross your reticule. When it does, fire your eels. Make sure you have opened your outer doors prior to firing or your firing will be delayed, which is bad. Assuming you estimated the speed properly, your torpedoes will hit.

It's important to remember to toggle the TDC and make sure that the gyroangle is tracking your periscope movements. I have screwed up more than one torpedo launch by failing to toggle the TDC inputs off and as a result your torpedo goes sailing off in the wrong direction.

You know you've got it when moving the scope makes a ticking sound. No ticking sound and your TDC is not set properly.

Convoy attack is the same, but the approach is more difficult because of escorts.

Steve

[Aktungbby]

Barker262!

[Kielhauler1961]

Originally Posted by BigWalleye

... And second, submerged firing based on hydrophone contact alone was so inaccurate as to be a waste of torpedoes. IIRC, there was never a successful hydrophone-only attack made by any submarine of any nation during the war....

Although the initial contact was confirmed by periscope, the rest of the attack was plotted by hydrophone bearings and predicted in 3 dimensions in the only recorded action of its kind...

HM Submarine Venturer sinks U-864 while both were submerged:

http://en.wikipedia.org/wiki/Action_of_9_February_1945

How many of us are so paranoid that we zig-zag submerged to avoid detection?

KH

[Jimbuna]

Welcome to SubSim Barker

[BigWalleye]

Originally Posted by Kielhauler1961

Although the initial contact was confirmed by periscope, the rest of the attack was plotted by hydrophone bearings and predicted in 3 dimensions in the only recorded action of its kind...

HM Submarine Venturer sinks U-864 while both were submerged:

http://en.wikipedia.org/wiki/Action_of_9_February_1945

How many of us are so paranoid that we zig-zag submerged to avoid detection?

KH

Thanks, Kielhauler, for expanding my knowledge base. I was unaware of this action and have corrected my earlier post. Three points: First, the action took place very late in the war, with much-refined equipment. Second, U-864 was running submerged on Diesels with a schnorkel, and had a noisy defective engine to boot, making her a much stronger acoustic source. Finally, while a German sub was involved, it was on the receiving end. Still this is the only successful hydrophone-only attack ever officially acknowledged. Very impressive!

[barker262]

Thanks to all for the replies. It's heartening to see that a PC game nearly a decade old can have such an enthusiastic following as you chaps.

I gather from some of the responses that the hydro contact of a convoy at long range can act as 'one contact'. I can see that being the case, but does the hydrophone operator call the contact as such? If he does, I could try and master that 4 bearing moving method to keep up while at a distance, get at least two of the critical factors, course and speed (I think you can get speed in the first 3 bearings can't you?) and then scoot ahead and pick a target as it come in view.

Now if the operator doesn't call the contact and I have to operate it myself, how do you read the heading, that is to say, I hear a contact how do I judge the center point? How accurate can you be?

P.S. I turned the headphones up to have a good listen, only to have the chief engineer yell, "getiefer eins null." Nearly tipped out of my chair, no wonder the escorts can find us.

[Shkval]

If the convoy noise begins at, let's say, 315 degrees and silences at, let's say 353 degrees, first subtract 353 - 315 = 38 then divide the result with 2, 38/2= 19, then add the result with first bearing 315+19= 334, 334 is the middle of a convoy. You will need at least 1/2 of an hour of time between measuring s... No the hydrophone operator cannot call the convoy as a single contact... it's all up to you...

[flag4]

Originally Posted by maillemaker

In bad weather I have made pursuits by hydrophone - dive to periscope depth and use hydrophone to get a bearing, then surface and drive hard for 10-20 minutes and then dive and listen, repeat until you get a visual. Usually you can stalk around them at extreme visual distance without getting caught. This is risky once they start carrying guns because at 1000 meters they will tear you up.

My attack approaches are relatively simple. I believe there was a historical uboat captain who did similar 90 degree attacks almost exclusively.

The first thing is to make visual contact with the target(s). Your Watch Officer will be able to provide you with an exact range and bearing, unless you have installed a mod to reduce the range accuracy. Plot this point on your navigation map.

Next you will have to eyeball the target to estimate the Angle on the Bow, and thus the target heading. Draw a line on your map from the point of the target along its estimated heading.

Now you have to drive your boat to an intercept position such that you will be 90 degrees to the target when it passes in front of you. If you are at extreme range (10,000 meters or more) and there are no escorts with radar you can drive your intercept on the surface. You may have to drive away from the contact and do an "end around" maneuver to get ahead of them.

Once you are ahead of your target and are driving your boat on a course perpendicular (90 degrees) to the target, drive until you regain visual contact. Dive before you are spotted or the target will start zig-zagging making your job more difficult.

Proceed submerged until you are within 1000 meters of the target course. You will need to make periscope observations frequently to make sure you are on the correct course and that you are closing with the target fast enough to make the shot. Ideally you want to be within 1000 meters when you fire - I prefer 700-500 meters ideally especially for lone targets.

While you are waiting for the target to cross your bow, go to your TDC screen (F6) and turn on the TDC. You'll set up for a 90 degree shot. It's easy.

Set the Angle on the Bow to 90 degrees starboard or port. Remember, this is from the target's perspective. If you are on the starboard (right) side of the target, then you want to set the AoB to 90 degrees starboard.

Next dial up the target speed. You can infer the target speed by watching it carefully and by noting the size of the bow wake. Like I said, I usually guess 7 knots. It is possible to do a "fixed wire" method of timing how long it takes the ship to travel from stem to stern across your non-moving periscope vertical reticule, but to do this you need a positive ID of the ship from the ID book to determine the ship's length. With GWX gold there are so many ships by the time you thumbed through the whole book and found it the war would be over. However, if you know the ship's length, and you can time how long it takes it to travel past your reticule, you can get a fairly accurate speed using this formula:

speed in knots = length in meters / time in seconds * 1.94

In order to get an accurate time either your sub needs to be stopped or you need to be driving directly at it making your speed irrelevant.

With map contacts on it is trivial to place a mark on the target on the map, wait 3:15 seconds, then make another mark and draw a line beween the marks. That gives you the speed in knots.

Like I said, I find it easier to estimate speed now.

So, input the speed into the TDC.

Center your scope on 0 degrees, and toggle the TDC. Now move your scope towards the target. At about 5-10 degrees from zero (depending on the speed of your torpedo setting) the gyroangle will hit zero. This is where you need to aim your periscope regardless of distance to target. That is the nice thing about the 90 degree shot - distance to target is irrelevant. There is no need to set the distance in the TDC unless you want semi-accurate stopwatch time-to-target estimations. Since I usually shoot at 500-1000 meters I leave it at the default 500 meters. If something doesn't go boom shortly after the stopwatch passes the red line it's time to consider what you are going to do next.

Now you just wait for the ship to cross your reticule. When it does, fire your eels. Make sure you have opened your outer doors prior to firing or your firing will be delayed, which is bad. Assuming you estimated the speed properly, your torpedoes will hit.

It's important to remember to toggle the TDC and make sure that the gyroangle is tracking your periscope movements. I have screwed up more than one torpedo launch by failing to toggle the TDC inputs off and as a result your torpedo goes sailing off in the wrong direction.

You know you've got it when moving the scope makes a ticking sound. No ticking sound and your TDC is not set properly.

Convoy attack is the same, but the approach is more difficult because of escorts.

Steve

cheers - that's great. I'm printing it off...its all a bit 'drop and run' I like that. has a rough feel to it - a real feel too.

[Pisces]

Originally Posted by maillemaker

...
At about 5-10 degrees from zero (depending on the speed of your torpedo setting) the gyroangle will hit zero. This is where you need to aim your periscope regardless of distance to target. That is the nice thing about the 90 degree shot - distance to target is irrelevant.
...

Nooo! That's a common misconception. Distance to target being irrelevant is only when the Gyro angle is zero or close to it. If you set yourself up being angled 45 degrees across the track (with AOB set appropriately for the bearing) while still aiming with 0 gyro angle, then it is also irrelevant. 90 degrees across the track only gets you his best broadside, and hence best margin of error for speed estimates. Distance is only irrelevant if the torpedoes do not need to turn. The minimum torpedo arming distance taken aside, that is.

Originally Posted by barker262

(I think you can get speed in the first 3 bearings can't you?) and then scoot ahead and pick a target as it come in view.
...

Nope only AOB, and thus course after considering the bearing in relation to your own course. Speed and range need for you to be displacing after the 3rd and look from a different vantage point to see where it crosses a forward projected semi-4th bearing. For the 3-bearing method, make and play around with (link)this. It has been incorporated in one or more of Makman's GUI mods.

But there are also other 4-bearing and even 5 bearing methods that allow you to be moving the whole time, described in the SH4 and SH5 section. Just do a search for hydrophone and names like Nefelodam, Kuikeg, Stoain and Makman (iirc the proper spelling of their names). You'll find them.

I too consider this just a method to get close enough, and get an estimate on their speed and distance. But it has to end in visual contact before torpedoes start swimming. Can't have friendly-fire incidents, you know.