information

[wiwi29]

hello everyone
how to calculate AOB used without the card, just used the periscope
thank you

[irish1958]

That is a difficult thing to do. There are several ways to do this and all of them depend upon experience. There are several threads and tutorials on the procedure. Do a title search of the forum for AOB and check out the various methods.
One thing you need to do, regardless of the method, is to keep checking and refine the result as the ship draws closer to you.
AOB just tells you the course of the approaching vessel in relation to your course. So on the map, you draw your course and the vessel's course and the angle where the lines intersect is the AOB.

[wiwi29]

thank you friend

[flag4]

'So on the map, you draw your course and the vessel's course and the angle where the lines intersect is the AOB.'

thats cool. i have always struggled with this. im no numbers and angles man - but that one sentence clarifies a lot for me, thanks irish

[unterseemann]

First welcome on board!
Calculate AoB with periscop is not very complicated and very very useful in manual targeting.
Let 's see it in images:

First, a 0° AOB, ship is coming directly to you


Now a 90° stb AOB




The left ship is 0° AOB, the right ship may be 2° stb AOB and the middle one 7-8° stb AOB


A 77°port AOB


As you see it's quite simple when AOB is near 0 or 90°. It's more difficult between 30 and 70°, in terms of accuracy. You have to "guestimate".
The only key is practice...

You can also determinate ship's course with only periscop:
Ship course= uboot course ( easy)+ periscop deviation ( easy) +180 (easy)+ AOB (if port) or -AOB (if starboard)


ex: uboot course:333 + periscop deviation +291 ( or -69) + 180 - AOB (cause it's starboard) so 333-69+180-10=434° as it is a 360° circle, 434° is equal to 74°.
Ship's course is 74, the only thing that is not known with absolut accuracy is AOB but here the supposed 10°stb AOB is very very close to the real value.
So now you can set up a nice 90° attack by changing course to 344

You don't need the map, don't need magical crew assists or auto updated bearing lines to perform it. Just look in your periscop!

[flag4]

hello unterseemann....

thanks for this, BUT.... it sounds like you know what you are talking about - but i have no clue at all..

[Pisces]

Originally Posted by flag4

'So on the map, you draw your course and the vessel's course and the angle where the lines intersect is the AOB.'

thats cool. i have always struggled with this. im no numbers and angles man - but that one sentence clarifies a lot for me, thanks irish

Unfortunately this is wrong (or just a special case, see below). It is not dependent on your course! It is dependent on his course, and where you are in relation to himself! AOB is the angle between the target's bow, and the view from him to you. (in other words from his bow to the center-line of the scope when you are locked on the target)

The above statement from Irish is ONLY true if you have the periscope pointed to your bow and the target is centered in view. But that is usually to late to consider a torpedo shoot!

If his bow is pointing straight at you in the view then the AOB is 0 degrees. If he is pointing exactly sideways in the view then the AOB is 90 degrees, and he is pointing either his port side or his starboard side. Do note which one it is! If the target is moving exactly away then the AOB is 180 degrees. As said, the angles in between are hard to judge. But it should come with experience. Another angle that is somewhat easy to determine is an AOB of 30 degrees. Then the apparent width of the target (how far away is the bow from the aft end) is halve of the width as if it had a AOB of 90 degrees, or how it would look if you looked side-on.


If you plot his positions on the map then you should be able to plot a line through them, and extending it to his future positions. This becomes the course of the target. If you need to know the AOB then plot the (current) position of the target on that line. Then draw a protractor (angle mouse-tool, "V"-like thingy): The first click needs to be on one of his future positions on the course line. (just somewhere ahead of his current position) The second click should be on the (current) position of the target. The third and last click should be on your own current location. The angle shown in the corner of the protractor tool is the AOB degrees of that moment. You should note if the angle (and thus you too) is on his left (port) side, or on his right (starboard) side.

Do remember that if the target is far away then the AOB doesn't change much in a minute. But as it gets closer then the AOB changes more quicker. When the AOB is 90 degrees then it is at it's quickest, and afterwards then it slows down to a crawl on the horizon again. So you need to be more quick with all this if he is within a few kilometers.

If you want to enter the AOB in the notepad then the periscope should be pointed at the target when you make up your mind on the number. But do not keep the scope locked as you are trying to enter it on the notepad. Unlock it when you are sure of the right AOB. Then you have all the time to enter it in the TDC or the notepad. Just keep the periscope or uzo pointed as it was until it is set. After that the TDC updates the AOB as you move the scope automatically.

If you make a course change after that then you need to figure out the AOB again from the start.

[Sailor Steve]

Here is a little something that should help:
http://www.subsim.com/radioroom/down...o=file&id=2902

[unterseemann]

Thank you Steve!
This tutorial is a must have and the link to the USN submarine fire control manual full of valuable infos
In the tutorial there is a sentence which makes me laugh: ' if you haven't mentally planned a firing solution at a passing ship while standing on the beach, you are a lightweight! '

[irish1958]

I stand corrected; what I should have said is that it is the angle formed by the line drawn from your location to the target's true course. I am sorry for the mis-information.
The problem with measuring the AOB (in real life) is ships zigzag, so what you estimate by periscope as the AOB is constantly changing. Once you know the target's true course, you can then use the AOB, figure out the speed (relative to the true course) and range (relative to the true course); and then you can guess where the ship will be so you can plan your attack. As in all things, including sex, closer is better.
We need practice missions with a merchant ship and a convoy zigzagging at moderate speeds and warships zigzagging at high speeds.
The reason the fast cruiser "Indianapolis" was sunk was it had burned most of its fuel racing the A-Bombs to Tinian and as a result didn't have enough left to get to the Philippines (where it was ordered by MacArthur) unless it cruised without zigzagging.