Japanese Sonar TMO
 

Its Dec 22, 1941, I spot the convoy returning from the Linguyan Gulf heading towards Formosa. I manage to get in front of it and have a good estimated heading of due north on the convoy. Its a huge convoy, maybe 30 or so merchants, 5-10 warships and 6-8 escorts, I didn't realize its size until after I submerged in front of it and waited for it to come. I realized that its spread out over at least 5nm or so and im within 9000 yards and Im smack in the middle of its path. So I figure since I read Ducimus' Uber AI explained, I know that at 250 feet, silent running, and engines at 50 rpm that I can theoretically slide through the screen and come to PD after the escorts are behind me. Nope! That don't work even at silent running and 250 ft I end up getting "spotted." Keep in mind that Im also below the thermal layer too. I'm "spotted" while still at max depth and silent running when I thought, no wait, I was told that the sonar in the early war doesn't have that kind of capability. Well, how would you slip by a screen in a situation like that? Also, I picked the biggest gap between escorts that I could see, dead in the middle of the convoy.

Yes TMO makes that harder.
Yes you can go deeper than your test depth.
Yes you should have been at 350, I'll run at the gauges maximum reading.
Yes shut your engines off AND be at silent running.

With a convoy that large simply max your depth go quiet and stop your engines.

1. Once the escorts have passed and you estimate they are 1000 yards . past you then, STILL AT ALL STOP, rise to periscope depth,
2. Fire forward and aft tubes and all available targets aiming at the farthest . target first in the group your shooting at,
3. Drop the scope head deep to reload at all ahead flank once below 100
. feet,
4. Maneuver to where you wish to pop up next and half way there drop your speed back to 2 knots.
Come to periscope depth repeat the above.

The escorts will have to spend time reaching your first launch point. If you have done this correctly you will not be there and they will not have picked you up at your new location until you fire your next volley. The convoy will be zig-zaging by this time so your next shot will be more difficult but even a miss in a convoy this size can reflect a hit in a ship farther away in the group if you get lucky.

If you plan this attack during night time hours you'll have even better luck if you attack on the surface. Many of the merchants would not have deck guns and the IJ escorts did not have radar.

At night I have ran between escorts on the surface, attacked the merchants then retired moving out between escorts again to reload and come back while they are still trying to find me.

Thank you, I have never went past the red needle on the depth bar because I believe in the stock game that its instant death at a certain depth. I am not sure because I havent played stock in years and only played stock for one campaign. Is there a chart somewhere or a file that shows active sonar capabilities for depth? I wouldn't change it but I would like to know for informative purposes. More information leads to better tactics. I thought 200 ft was the max capability for early war sonar.

They're numerous other values you have to factor in on how good enemy sonar will get you, weather, sub profile, silent running, etc...

Well being able to stay submerged past 300 feet (i think maybe the conning tower was still above 200ft so the active sonar cone was catching the tip) I haven't once been "spotted" when attacking a convoy with that approach. Ive ran into at least 4 more convoys since and had success in all of them. Playing with no map contact updates, I am not really able to determine a precise speed and course though. Im just having to eyeball the passive sonar and determine a general direction until I can visually see the ships. Then I observe and estimate a AOB to get some course then shoot off in front of it and wait. I know the 4 bearing method but it seems impossible without bearing lines (which I dont want) when tracking a convoy. What is the best way to find a suitable position for attacking a convoy without using any kind of help from map updates or using the watch officer for range estimation on visual contacts?

edit- The reason I am asking is because I find that sometimes even while being out of visual range that if im going flank speed (making a lot of noise) that a destroyer hears me then comes and finds me. I had a task force on my sonar and I couldn't even see the cruisers yet but a dd just came rushing at me. So would like some advice on determining course and speed (even if only good guestimations) without having to visually see the ship.

If you're using TMO, learn to use the radar. With contacts off, I'll use radar to get course and speed. Since you're doing the work, it helps to pause the game while you make your marks. If you're using TMO alone, most of the groups zig about every 10nms, so I try to track it for 3 legs and determine a base course. The goal is to get in a position along the course, so if you catch a zig, you can get off a shot, so draw a line and mark a spot way ahead and get there and dive. Once I get a visual with the scope, I'll start fine tuning where I think I need to be. Be precise with your last two scope peaks and stad properly, check speed and AOB and fire a spread...

Like Armistead said, you can use radar, If you don't have radar, there really isn't a good way to determine course and speed, without visual observation. This usually means careful observations, judgment, and lots of plotting. If it was practical to stalk and target enemy ships without recourse to visual sightings, subs wouldn't need periscopes. Not every contact could be intercepted, and not every interception would result in a successful attack.

Also, it will help you to know what a Normal Approach Course is, and why it was used. However, it doesn't tell you anything about the enemy's course or speed.