Sonar and radar usage

[Fader_Berg]

Is it safe to use radar to spot ships, or will it just be a call for trouble? I've just merely survived an air raid in the atlantic. (Some new yellow planes, [yes, I'm new to this] which are terrifying compared to the ones around the british islands). I realy don't want to call their attention. But the atlantic is big and a sight of <=~7000 meters, practically means nothing.

I guess sonar shouldn't be used against destroyers. But how good is the precision of it, (by length to target)? Is it closer to truth than the WO? Is it only usefull in bad weather, and so on? How many pings? Does the target notice it?

How are you all using these things?

[tomfon]

In my opinion radar doesn't help much for two reasons. First, destroyers and aircrafts can and will detect you. This means trouble for your Uboat and your crew... Second, i am not so sure about its effectiveness. In fact, i believe it can detect sh!t! By the time you start using the radar the Allied A/W will be quite effective. I think that using the hydrophone to detect a ship or a convoy underwater is much, much better cause you can maintain your stealthiness. Not to mention that the early radar versions - at least, have shorter range than the hydrophones. So, why take the risk of being detected by an airplane while hunting a convoy? Last, don't use the sonar to ping destroyers and don't use it to ping merchants which sail within a convoy. Unfortunately i don't know more details.

:salute:

[Jimbuna]

Your radar will be detected (when turned on) by sea and air assetts.

Your sonar will not.

[Rafael]

I suggest to avoid using radar. My experience is quite bad for you and your crew. The radar range is too short and I agree with Tomfon, use your hydrophones submerged!

BdU should learn me that at school and inform me better about our bad radar system. :know:

[PavelKirilovich]

German radars get a bad rap during WWII for some reason. They had some systems which were quite good by the standards of the time and other systems on par with Allied and Soviet technology. And of course, a few subpar systems. The problem is not so much the technology fitted to the boat, as the platform to which the technology is fitted.

The radar horizon is pretty limited from a U-boat. You've only got the emitter a few metres above the ocean's surface and the emitter is space-constrained, the number of transmit and receive modules that can be fitted to the array is limited by the need to field a compact system. Power aperture and power aperture product is thus limited; but peak power was reasonable. The Germans did pretty well with this set, the key problem is what I mentioned earlier, it's only a few metres above the water.

The reason we see radars and lookouts stationed on the highest points of a ship is to artificially increase the distance to the horizon. It's a trigonometry thing. The higher a radar, the further it can see because geography (earth curvature) doesn't prohibit the signal from propagating back to the receivers. However, the enemy's radar warning receivers and direction finders only need to detect the signal, whereas we need to send a signal out AND get it back. Sod's law applies: the more **** you need to do, the less likely all of it is going to get done.

So what the radar does for you, in effect, is act as a "I'm over here" beacon to enemy ASW efforts. You want to run under full emissions control. Manually check every time you surface to make sure the radar operator/radio operator isn't running the radar of his own initiative. Nothing is more painful than being bounced by a hunter-killer group when your batteries badly needed a recharge and your CO2 levels are dangerously high.

It's OK to ping capitol ships with your sonar. It's not OK to ping ASW vessels with your sonar. Capitol ships are escorted by ASW vessels. The reason it's OK to ping the big gun big tonnage targets is because we don't have good shock dampening systems, sonars weren't typically fitted to large gun combatants because of space constraints and shock damage that would be caused by the gun's recoil to the system. Same reason full broadsides aren't fired: they'll shake the boat apart.

[Bosje]

in my experience, radar is only useful in zero visibility conditions, when you know that a single merchant is out there somewhere in the rain and fog but you can't see a thing

of course, those conditions often come with 15 m/s winds which means the early crappy radar gets switched off every time the boat takes a plunge in the waves.

and unless i'm wrong, in real life those conditions were regarded as too terrible for attack operations

[Leandros]

I find, as the war proceeds, that using the radar is not wise. However, the enemy's use of radar is of great value. Both to detect convoys as well as approaching aircrafts. To find you they necessarily must use their radar - and they do!. The aircrafts can usually be verified by their much faster approach speed. If your RWR detects two or more radar signals it usually indicates a convoy in the vicinity...! Sit tight a little while and observe the movement of the transmitting vessel and you soon have its course - and the convoy's...!

If a Swordfish approaches there is a carrier near by.....:03:....

[Lt.Fillipidis]

From my experience, the radar can detect a destroyer before she even comes in visual contact in perfect conditions. That means more than 12k meters.
Just make sure to turn it off when you close in. :ping:

[Contact]

German radars get a bad rap during WWII for some reason. They had some systems which were quite good by the standards of the time and other systems on par with Allied and Soviet technology. And of course, a few subpar systems. The problem is not so much the technology fitted to the boat, as the platform to which the technology is fitted.

The radar horizon is pretty limited from a U-boat. You've only got the emitter a few metres above the ocean's surface and the emitter is space-constrained, the number of transmit and receive modules that can be fitted to the array is limited by the need to field a compact system. Power aperture and power aperture product is thus limited; but peak power was reasonable. The Germans did pretty well with this set, the key problem is what I mentioned earlier, it's only a few metres above the water.

The reason we see radars and lookouts stationed on the highest points of a ship is to artificially increase the distance to the horizon. It's a trigonometry thing. The higher a radar, the further it can see because geography (earth curvature) doesn't prohibit the signal from propagating back to the receivers. However, the enemy's radar warning receivers and direction finders only need to detect the signal, whereas we need to send a signal out AND get it back. Sod's law applies: the more **** you need to do, the less likely all of it is going to get done.

So what the radar does for you, in effect, is act as a "I'm over here" beacon to enemy ASW efforts. You want to run under full emissions control. Manually check every time you surface to make sure the radar operator/radio operator isn't running the radar of his own initiative. Nothing is more painful than being bounced by a hunter-killer group when your batteries badly needed a recharge and your CO2 levels are dangerously high.

It's OK to ping capitol ships with your sonar. It's not OK to ping ASW vessels with your sonar. Capitol ships are escorted by ASW vessels. The reason it's OK to ping the big gun big tonnage targets is because we don't have good shock dampening systems, sonars weren't typically fitted to large gun combatants because of space constraints and shock damage that would be caused by the gun's recoil to the system. Same reason full broadsides aren't fired: they'll shake the boat apart.

Yes, I agree with everything you said here. But as far as I know in SH3 you can't be detected if you use a sonar to get target range or echolot to measure the depth what I realy find a big lack in realism..

Speaking about detection of noises underwater by DD's. There are couple more old issues which I find odd and unrealistic. The playing gramaphone can't be detected by ASW vessels and I think ASW vessels should be able to hear incoming torpedo sound at least in calm sea state ?

[BulSoldier]

They could hear the torp (IRL) but you must agree that torps are rather small and i doubt it will be easy as detecting a ship.I presume the that torps are quiter than the normal merchant ships ?

[Contact]

They could hear the torp (IRL) but you must agree that torps are rather small and i doubt it will be easy as detecting a ship.I presume the that torps are quiter than the normal merchant ships ?

You can clearly hear them runing on your own u-boat hydrophone so the same should go for ASW vessels, dunno how it realy was in RL, but in SH3 if you can hear it runing the enemy should be able to hear it too.

[Jimbuna]

You can clearly hear them runing on your own u-boat hydrophone so the same should go for ASW vessels, dunno how it realy was in RL, but in SH3 if you can hear it runing the enemy should be able to hear it too.

This is where the game engine goes 'funny'.....it can see the wake of the steam torpedo but it can't hear the sound of either of the torpedo screws.

[PavelKirilovich]

Couple comments:

i) Torpedoes can be difficult to pick up on passive sonar because the emitting source is behind a long object (e.g. the torpedo itself) and if the conditions are less than optimal (and when are they ever optimal?) you get some weird sound propagation issues, from what I understand. However, for long range shots the vessel should detect it (as the angle-on-target is large) and other ASW vessels should detect it; it's a very distinct high pitched "Screeee" noise on most fish.

ii) I like Leandros's electronic warfare technique. I use it myself. The game engine probably doesn't model this, but I do it anyways just to be safe: I run at decks awash and turn in towards the emitting signals to reduce my radar cross section. If the signal is moving quickly (airplane) I crash dive, because I skip a IXD2 at the moment and that thing takes forever and a day to get under the surface. (You can tell I'm used to my good ol' VIIC...)

iii) Bulsoldier: Size relates only to detecting with active sonar (ASDIC) arrays, not passive. If it's making noise, you can detect it on passive regardless of its size. Contact, by association I wish they'd hear me launch torpedoes. I'm limited to compressed air launches here, water-ram ejection didn't happen until fairly recently, so they should at least have some idea that someone just shot at them when conditions are reasonable. The gramophone thing always gets me; though I do like singing "Lili Marleen" while being depthcharged.

[Captain Birdseye]

Another quick question,

Am I right to have only one guy operating both the hydrophone and radio, by having him on the radio when surfaced, and hydrophone when not?

[Contact]

Contact, by association I wish they'd hear me launch torpedoes. I'm limited to compressed air launches here, water-ram ejection didn't happen until fairly recently, so they should at least have some idea that someone just shot at them when conditions are reasonable. The gramophone thing always gets me; though I do like singing "Lili Marleen" while being depthcharged.


The launch of a torpedo the same as door of torpedo tubes opening/closing should be also heard by hydrophone if ASW vessels crew is enough competent or elite I think. Also it should be rare event to detect you launching a torp, since sonar guy has to listen the right bearing (listening you) to trigger alarm on board and convoy around if there is one.

[Contact]

In my opinion the use of a radar should be avoided. I use only the Radar Warning Receiver (RWR) to notify me of incoming trouble at least temporarily :)

[RoaldLarsen]

Another quick question,

Am I right to have only one guy operating both the hydrophone and radio, by having him on the radio when surfaced, and hydrophone when not?

I believe that their ability to detect things depends on the current efficiency of the crew in the room, as indicated by the green bar at the top of the room. Having only one crewman in the room lowers the efficiency and therefore may tend to result in you missing things.

[Jimbuna]

Another quick question,

Am I right to have only one guy operating both the hydrophone and radio, by having him on the radio when surfaced, and hydrophone when not?


Have one at each of the two stations for optimum performance.

[Schroeder]

The launch of a torpedo the same as door of torpedo tubes opening/closing should be also heard by hydrophone if ASW vessels crew is enough competent or elite I think.
I don't know. Did they constantly listen while steaming through the Atlantic? I think you can only hear things clearly when going rather slow (there are plenty of background noises in RL that aren't integrated in SH3 and 4). I guess that they were only listening when they thought that a U-Boat was near by. That would give us the option to strike first without warning. After they are alerted they should be able to detect torpedoes but not until then.:yep:

[Contact]

I don't know. Did they constantly listen while steaming through the Atlantic? I think you can only hear things clearly when going rather slow (there are plenty of background noises in RL that aren't integrated in SH3 and 4). I guess that they were only listening when they thought that a U-Boat was near by. That would give us the option to strike first without warning. After they are alerted they should be able to detect torpedoes but not until then.:yep:

I think escorts were always listening with pasive sonar when guarding the convoy

[PavelKirilovich]

Escort vessels equipped with ASDIC and hydrophones always had those stations "full up" because contact with U-boats can happen at any moment. Not everybody makes night attacks as the manual says. The limiting factors with the efficiency of passive sonar and active sonar arrays in WWII were primarily hardware-based, you could only generate so much power and transmit it effectively, and you could only amplify sound so much because of the technology limitations of the time.

Flow-noise blankets the sensor and you have to be running below a certain speed to make use of your sonar systems. I haven't seen a convoy with merchantmen running too fast to be unprotected by ASDIC/hydrophone, but I have seen taskforces of RN and USN vessels moving so fast that I should have been able to sprint into a close range firing position, empty my tubes, and dive away without them knowing anything until my targets turned into raging infernos of suck. This was not the case, sadly.

You should be able to hear a torpedo launch (compressed air ejection) even if your sensor is mostly turned away from the launch point, because water doesn't compress and therefore carries sound energy (essentially miniature shockwaves) very well. You won't get a bearing, and you won't get any sort of reasonable range information (hard to estimate from passive plots anyways), and by the time you hear it the launch will have been long since completed and the boat will likely have repositioned itself. But you should be able to hear it.

Small mechanical noises like the torpedo doors opening you should be able to hear when you're monitoring a contact directly and the sonar conditions are favourable.

Sidenote: What depth does the game model the thermocline at? I hear things like 200-250m.

[BulSoldier]

IIRC the game itself doesnt model them, but sh3 commander does make random asdic max depth detection in order to simulate the thermal layers.(if that is what you mean?)

[PavelKirilovich]

That is what I mean. Thanks! Or Благодарности!, if I remember my very basic Bulgarian correctly. :DL

[BulSoldier]

How nice of you and yes you are correct.

[Contact]

That is what I mean. Thanks! Or Благодарности!, if I remember my very basic Bulgarian correctly. :DL

Благодарю more likely :)

[BulSoldier]

It is Благодаря actually but the word he used is just as right, may be not so much in use in daily conversations nowdays.

[PavelKirilovich]

Yeah, the Bulgarian I know is Yes/No/Thanks/Please/"No, sorry, I'm not interested in invading Romania today" and I'm joking about that last one. It was brought up in Russian class where we were discussing the differences between Tsarist-era Russian and Communist-era Russian, so if my Bulgarian is out of date I wouldn't be surprised.

Would one, when speaking Bulgarian, conjugate the word to match the Slavic "I/We/Them/Us/It/He/She" ending? "I thank you" (Ya "blagadarnostyu") or "We thank you" (Miy "blagadarnostyom") for example, or is it simply that the word has evolved with the language?

[BulSoldier]

Well it is like this about the word thank you (it is hard to translate in such manner)

I thank you - Благодаря ти or (Аз ти благодаря - but that sounds a bit odd and i think is gramaticly incorect)
We thank you - Благодарим ти

thats it for first person.In this case "I" (аз) in the beggining shouldnt be said.
It is a bit hard to explane since this is my native language and i understand it because this is how always was (to my perspective).

Howeever i think we are getting a bit offtopic here :)

[Contact]

<A voice from the distance> Hiiiiijackers! :haha:

[PavelKirilovich]

Bulsoldier: Not too dissimilar to Russian then. I understand. Thanks.

Contact: Well, at least you didn't say "pirates". I don't want to be shot by the US Navy in the Gulf of Aden in the middle of the night. (Booyeah. Recent events reference +10).

[Uber Gruber]

In Real Life how did a usual U-Boat execute its patrol ?

For example, did they submerge every 20km to perform a hydrophone sweep to see what's in the area ? Or did they mainly run on the surface at 2/3rds speed and only submerge when forced to ?

I ask because there are scenes in Das Boot when the U-Boat is toughing it out in a storm when its obviously better to be 60m down in calmer water and where you'd have more chance of detecting something using the Hydrophones than eyes.

Yet in books i've read there is no mention of submerging every 20km to make optimum use of the Hydrophone, the lasting impression is that they only submerged when they had too aside from the daily dives to fine tune the trim.

My ultimate goal is to employ the same patrol procedures as in they did in Real Life (in between contacts) so any help here would be greatly appreciated.

Mucho Cheerso...:hmmm:

[Contact]

Usually u-boats dived if they spoted an aircraft or DD approaching. You can put this to forced dive if you want.

U-boats also used a bad weather to cover themselves from patroling aircrafts and on purpose remained on surface to jump to another area more quickly. But of course if seas were rough, remaining on surface had caused larger fuel consumption. So it was up to captain to decide what to do depending on circumstances.

[Uber Gruber]

Thanks for the reply Contact....continuing in the same vein, how many times would they have submerged to perform a Hydrophone sweep of the area during the day ?

I imagine they only dived once a day (the trim dive) and then only when it was necessary, i.e. forced to by plane or very bad weather.

I imagine they only used Hydrosweeps when they were in the vicinity of a possible contact, e.g. another u-boat beacon or radio report of possible contact in area such and such.

But then again, I could simpy be imagining things.

Cheers....

[Contact]

Thanks for the reply Contact....continuing in the same vein, how many times would they have submerged to perform a Hydrophone sweep of the area during the day ?

I imagine they only dived once a day (the trim dive) and then only when it was necessary, i.e. forced to by plane or very bad weather.

I imagine they only used Hydrosweeps when they were in the vicinity of a possible contact, e.g. another u-boat beacon or radio report of possible contact in area such and such.

But then again, I could simpy be imagining things.

Cheers....

I think it also was due to where the u-boat was patroling. If it was the heavy naval traffic area divings were more often to search for potencial targets. However I'm not sure was it as a rule on how often dive procedures had to be made.

More chances to spot a target was submerged since as you know hydrophones could pick up screw noises from much greater distance then eyes of watch crew did.