Convoy Interception Methods

[bigbear948]

1.How do you intercept convoys on the navigation map ?

2.And what is the maxium range you should intercept from ?

Intercepting seems really hard, I have no idea how to intercept, use the map tools(except managing the Sub's own course), and how do you take into acount the convoy's and your own speed ?

The navigation Turtorial in Submarine school is far too simple.

[Pacific_Ace]

Ive always found this works extremely well in SH3 and pretty well in SH4. The reason for the difference seems to be that in SH4 when a contact is listed as going for example East that doesnt necessarily mean its traveling at a heading of 90 degrees. It could be going 80, it could be going 110.

http://alexbret.perso.cegetel.net/in...epting_Targets

[SteamWake]

Biggest thing is to get ahead of them. Determine their course then lay in wait.

Simple as that.

Realize that often you cannot accomplish this simple task. To do so would burn way to much fuel and you just have to sigh and let it go.

[Rockin Robbins]

The real subs without radar had it worse than we do and still managed to intercept, so let's do it their way. First decide whether they are moving left to right or versa visa. Let's say they are tending to the right. Then turn right and put them on your 270º bearing. Hit the gas (assume they are going fast to begin with.)

Now observe. If their bearing stays the same over time you are on a collision course, keep it up. You're going to have a very short encounter with about one shot if you're lucky but you will be able to intercept them.

If the bearing changes more toward stern, in this case decreasing as time goes by, then you will pass in front of them. Keep it up. You want to get ahead and submerge off the track to shoot them as they come up on you.

If the bearing is getting larger than 270º, changing more toward the bow, that means that they will pass the point where your courses cross ahead of you. You will have a hard time getting in position for a shot. Change your angle of attack to put them at 270º again and see what happens. If you continue this you will eventually end up on a parallel course. Then if you are faster than they are, maintaining the 270 bearing will put you on a more and more converging course to end up ahead of them. Submerge off-track and wait for your shot.

These are VERY GENERAL guidelines which assume you know nothing more about them than "there they are." You can do much better than that if you can establish their course and speed. Basically if you are behind them, you want to end around at a range where you will not be detected, but you can maintain contact with them until you get far enough ahead to converge on their track, submerge and ambush them.

[Frederf]

First I'd like to call an "intercept" the process of going from intelligence about a contact (Flash traffic, navigation map square mark, whatever) to when you actually acquire the contact using your own sensors (visual, sonar, radar). Approaches are maneuvering with a contact followed by own sensors to the critical point (4000yd or so) and attacks are from critical point to torpedo launch. It's good not to confuse these phases with each other since their goals and means are quite different.

The nature of a contact intercept depends on quite a few things, none the least of which is the quality and style of contact information. In RSRD campaign (a mod) I very, very rarely get the stock square-with-tail contacts. More often it is the Flash radio message something like "Intel reports convoy traversing Formosa Strait AM Dec 21." This can be 1 to 3 days before Dec 21. The time frame could be from 12:01am to 11:59am that day. I'm going to assume though that you're working with the standard stock-type navmap contact square. Sometimes you'll get tail, no tail (depending on mod) or even pretty accurate course and speed info through a radio message.

How far depends on your patrol schedule, fuel, and confidence at intercepting. If you're confident and can see that the contact has to pass through a specific narrow waterway in just the right place you can have success at long, long ranges.

At the most basic, the interception problem comes down to predicting where the target's going to be and traveling there to show up at the same time or perhaps earlier. There are a great many choices of where to go as the target's going to be different places at different times. Just as there are different choices of meeting location, there are different reasons why you would choose one over the other.

More often you want to get to the contact as soon as possible. This will reduce the area the contact might be due to uncertainty in the speed and course as well as reduce the chance that the contact changes course. Submarine speed will be high so fuel use will be drastic for long distances. Encountering aircraft can ruin your average speed as well.

The math/geometry in the wiki link looks like black magic but it's nothing terribly special. What you're doing is setting up a mini-triangle where the length of two sides are known (your speed, contact speed) and the angle between those two sides. After you figure out the "intercept triangle" you merely scale it up so that two points are your position and the contact position. The last corner is the "meeting point." It's easy to check the math once constructed as the time for the contact to reach the meeting point and for the sub to reach the meeting point should be the same.

Given a speed and course range you end up getting windows at each time beyond the contact time. (Beware that the contact time can be much older than the time the marker popped up on the map) If the contact is moving 5-9 knots Westerly you can draw a window that has edges that are courses 247.5° and 292.5° (any more and it would be SW or NW instead of W) and ranges 5nm and 9nm. After an hour the contact could be anywhere inside this curvy angley box. If the boxes start to get bigger than your sensor range or how much ocean you can cover in an hour the chance of intercept goes down accordingly.

I often will set course for the far corner (fastest possible contact speed, least-desirable contact course) of the box that I can reach in time (maybe it's the 5 hr box) so that if I guess wrong I've pretty much trapped the contact and likely will have stumbled across him on the way to his "worst position" if approaching from the rear. You can also shoot for "center of window" or "center of fast edge" and then search from there. I like to very quickly dive and sonar sweep every 30 minutes once in the current window, especially if the visibility is limited.

Forget the temptation to try to get well ahead of the target and wait. It is almost always better to contact the target immediately even if from a poor angle and maneuver keeping the smoke on the horizon. Trying to be clever can lead to the target changing course or being far from your estimates and completely bypassing you.

[Pisces]

Here is a classic tutorial on how it can be done with SH3:

http://www.subsim.com/radioroom/showthread.php?t=88961

(whoops, the same technique as that wiki link)

Look for post 41 on the second page. A good summary picture of the procedure. Allways make these kind of drawings based on where the contact should be right now!. Especially if the contact report is hours old.

Allways go as fast as you can, top-speed, or flank if fuel is not an issue. But readjust the drawing if weather is slowing you down. Then the contact has the least amount of time to move away and the search area stays limited in size.

As for how far away you can depends on experience, the capabilities of your boat, and on the situation. Knowing his speed accurately is most important for long range intercepts. But if you got just a speedrange it's wise to use a worst-case speed. Then you'll allways end up infront of it, and can turn to meet the contact along it's course if it isn't there. Also meet him at top speed since you can loose it if it makes a course, or speed, change in the meanwhile. If you can't find him at all, though luck, but you did your best.

Whenever you arrive at the intercept location, and the contact actually did have the assumed speed, the target may still be outside of visual range due to it having a course slightly off from the reported course. So you will have to rely on radar or hydrophone (sonar is too short) to extend your detectionrange. The reported course (N,NNE,NE,ENE,E, etc. ) are all in steps of 22.5 degrees, which means that the actual course can be 11.25 degrees on either side of reported. You need to fit your best sensor range (circle) within such a 22.5 degree wedge to determine how far you can let the contact move (since time-stamp of contact report) before he might sneak past undetected on the fringes of detection range. Roughly speaking this is 5 times your maximum detection radius. So if your radar has a range of 30nm (60k yds) make sure you can be at the intercept point before he has moved 150nm or don't bother to intercept at all. Beyond that his chances of of a lucky undetected escape increases.

To make that visual: Draw a courseline for the contact of 5-times-sensor-range from it's origin point. Draw a circle centered at the end of the line with a radius the same as your best sensor. Draw another 2 lines starting from the contact origin point with the ends touching on either side of the circle. You should get a drawing that looks like an ice-cone. If your intercept course doesn't intersect it before the center of the circle you should forget about it.

The above drawing also solves the issue of whether or not to intercept a contact that is allready moving away from you. If the intercept drawing (with the ice-cone) says you can get it in time, don't second guess it, but GO FOR IT.

[Rockin Robbins]

Now, technically, what I wrote about above is approach tactics, meaning that you have sensor contact with the target, and Frederf has written about intercept tactics, meaning you have no sensor contact with the target. My piece was based on the Submarine Torpedo Fire Control Manual, Chapter 9, Submerged Approach and Attack Practices. This is applicable also to surfaced approaches, but since it was written for the much more restricted battery powered submerged submarine, incorporates the most efficient methods for obtaining proper firing position and transitioning from the approach phase to the attack phase.


Always begin the approach by heading directly at the target. Then observe whether the bearing opens up to the left or right. That will determine whether to put the target on your starboard or port beam.

The normal approach course (NAC) of your submarine should be keeping the target on your beam and moving in the same direction as the target. If you determine the AoB is large you can open that up to a 100 or 110º angle to allow for possible high speed of the target. If the AoB is below 45º you'll want to reduce that approach angle to compensate for the fact that the target is headed more directly toward you. Remember that if the target is moving from right to left, you'll have to subtract that desired angle of approach from 360º to yield the course to steer. Let's say your target bears 0º, your NAC will be 360-90=270º. Then you find the AoB is close to 90º or even larger, so you open that up by 10º to course 260º or even 250º. Clear as mud?

There is much more detailed information in the manual itself, linked above.

OK, Fred, am I blind? Where's that wiki link?