Convoy direction

[ddiplock]

Is there an easy way to work out which direction a convoy is heading if you can only hear it on your passive sonar??

I was only 2 days out of Manila, when I picked up a convoy on my passive sonar. I moved into what I THOUGHT was a good attack position to disover the convoy was actually heading the other way, and was in fact a Japanese Task Force filled with battlecrusiers and battleships. I had to let them slip away on my first patrol, as I couldn't get into an attack position, and couldn't risk surfacing for fear of being spotted :(

Cheers for any input guys :)

[Ducimus]

It' kinda cheating because contact lines give real distances, but just place a mark. Advance the time compression for a few mins. Place another mark, draw a line between the two. Instant course heading of convoy.

[mookiemookie]

That's assuming you're not using tater's campaign layers where convoys zig zag. ;)

[Ducimus]

Then you just observe them longer. They zigzag from 9 to 16 kM intervals. Then you just mark the point at which they zigged, and project a track out at 9 to 16KM from that point, and plan your endround attack via time/speed chart and get into position before the next anticipated zig.

[Rockin Robbins]

Then you just observe them longer. They zigzag from 9 to 16 kM intervals. Then you just mark the point at which they zigged, and project a track out at 9 to 16KM from that point, and plan your endround attack via time/speed chart and get into position before the next anticipated zig.
An end around on a 20 kt convoy of warships might have to be timed with a calendar!:doh:

Many times in the war subs were faced with exactly your situation and just watched 'em fly by just out of reach. Speed is the best anti-submarine tactic, just ask the skipper of Shinano. :yep:

[joegrundman]

But that, as you say, is cheating.

If you don't play with map contact updates on then there are two ways of doing this.

One is to perform target motion analysis which is a little complicated, and requires you to be stationary which risks losing your opportunity to get a kill

the other way, which i use, is elaborated in a file you can get from my sig. It works best if you have built yourself a Submarine Attack course finder whiz wheel.

However if you haven't got a SACF, nor the patience to build one, here's how to do a simple version. You need to print yourself the table below.

Once you have made sonar contact go to medium speed and turn to point exactly at the contact direction.

Listen to the bearing of the contact. If the bearing to it decreases, it is going to show you its port side, if it increases, it will show you its starb'd side.

Once you have determined that, turn 90 degrees to port or starb'd accordingly and try to bring the target exactly on your 90/270 degrees.

Start the chronometer. You want to adjust your speed so that over a period of 3 or 4 minutes, the bearing to the target hasn't changed.

You are now on a collision course and will eventually meet the target.

Now pay attention to other details to obtain a rough speed estimate. Is the target travelling at slow, medium or fast speed, is it a warship or a merchant? Have there recently been radio contacts advising of a ship in the vicinity? USe this information to gain an estimate of the target speed.

You can then estimate the AOB of the target for your speed esitmate using this table. Do this for a couple of different speed estimates, and you have an approximate target course by the usual method of converting AOB to course!

Sub speed
x --------------3kts ----4kts---- 5kts ----6kts ----7kts
Target speed

5kts ----------AOB37 ---53 ------90 --------------- -
6kts------------ 30 -----42------ 56 -----90 ---------
7kts------------ 25 -----35------ 46 -----59------ 90
8kts ------------22 -----30 ------39----- 49 ------61
9kts ------------19 -----26 ------34 -----42------ 51
10kts -----------17 -----24 ------30 -----37 ------44
11kts -----------16 -----21 ------27 -----33 ------40
12kts -----------15 -----20 ------25 -----30 ------36
13kts -----------13 -----18 ------23 -----27------ 33
14kts -----------12 -----17 ------21 -----25 ------30
15kts -----------11.5 ---15 ------19 -----24 ------28
16kts -----------11----- 14 ------17----- 22 ------26

[ddiplock]

I shall take Ducimus's suggestion under advisement, I wasn't aware that the sound lines on the map revealed the actual distance, I thought it just gave a rough estimate as to the direction of the convoy :) plotting points as the lines move will be an excellent way to track the course of a convoy :)