Sonar Question

[Dili]

I am looking for diferences in Passive Sonar and Active Sonar effectivness in first half of war. I mean how many times a ship with only Passive Sonar was less effective than one with also Active Sonar?

Thanks.

[Yamato hugger]

Its a game. Games have limitations.

[ChezDaJez]

ORIGINAL: Dili

I am looking for diferences in Passive Sonar and Active Sonar effectivness in first half of war. I mean how many times a ship with only Passive Sonar was less effective than one with also Active Sonar?

Thanks.

Its difficult to use both active and passive sonars at the same time depending upon the frequency and pulse repetition of the active sonar. Every time you ping the active sonar (which puts a very high level of noise in the water), you blank the passive sonar. The lower the frequency of the active sonar, the more passive blanking that can be expected.

In addition, the use of passive sonar to find a submerged submarine in or near a convoy or surface TF is an exercise in futility unless you are dead on top of the sub and know exactly what he sounds like. The same with using passive sonar near coast lines. Environmental noise from surf and wave action will help hide a sub's noise.

Active sonar is relatively ineffective in shallow water and or with hard bottoms that cause a lot of reverberation.

The thermocline has a huge effect on both depending upon its negative or positive gradient.

Chez

[bradfordkay]

Luckily, Chez' ASW crews in the game aren't as knowledgeable as he!  [:D]

[Dili]

...I just want to know how i should rate a DC harge with only passive sonar and another with active sonar support(1940-1943 technology). How much chances the active sonar ship has over passive one as all the rest being equal.

[AW1Steve]

ORIGINAL: bradfordkay

Luckily, Chez' ASW crews in the game aren't as knowledgeable as he!  [:D]

Actually , the ASW crews had more knowledge then we give them credit for. Their equipment wasn't all that developed , and ASW oceanographics really gained it's hey day in WW2. But even today, most of the Pacific is lousey from an ASW enviroment point of view. To hunt subs you want cold,deep water. Shallow warm water is a real bytch requiring the use of active sonar for limited range. The world war two subs definately understood how to use the thermocline and the layers. It's all through every submarine account that you read of ww2. But without towed arrays,disposable sonar bouys and other modern tech, there really isn't much to do about it. 1943 saw the introduction of modern ASW methods (acoustic homing torpedo's, disposable sonobouys,Magnetic anomoly detection,bathothermy sono bouys,hedgehog,and expanded passive sonar). But they were just scratching the surface, so to speak. [:)]

[ChezDaJez]

ORIGINAL: Dili

...I just want to know how i should rate a DC harge with only passive sonar and another with active sonar support(1940-1943 technology). How much chances the active sonar ship has over passive one as all the rest being equal.

From a targeting standpoint, active sonar has it all over passive sonar in WWII. Range was extremely difficult to obtain with passive sonar and bearing accuracy left a lot to be desired. Even with today's sensors, passive range determination can be a real pain to obtain.

If I were to quantify a hit percentage based solely on passive sonar, it would be less than 1% chance of that DC getting anywhere near enough to casue any damage.

The only benefit passive sonar has over active sonar is that the target may not know he has been targeted by passive sonar.

Chez

[Bullwinkle58]

ORIGINAL: Dili

...I just want to know how i should rate a DC harge with only passive sonar and another with active sonar support(1940-1943 technology). How much chances the active sonar ship has over passive one as all the rest being equal.

In addition to the factors already mentioned, range is incredibly important. WWII passive sonar was all Mark I human ear--no signal processing. The Pacific, especially in shallow water, is more biologically active than the Atlantic. My dad was a Pacific sub chief sonarman in a Guppy-modded sub, and he knew hundreds of species by their creaks and clacks.

In WWII, active was the only game in town outside of very close ranges. And if there was weapon activity, such as the first DC, passive was even more useless.

I'd say anything outside of, say, 2000 yards, passive woudln't have gotten you any data in many cases, but that's a guess.

[pompack]

ORIGINAL: Bullwinkle58

ORIGINAL: Dili

...I just want to know how i should rate a DC harge with only passive sonar and another with active sonar support(1940-1943 technology). How much chances the active sonar ship has over passive one as all the rest being equal.

In addition to the factors already mentioned, range is incredibly important. WWII passive sonar was all Mark I human ear--no signal processing. The Pacific, especially in shallow water, is more biologically active than the Atlantic. My dad was a Pacific sub chief sonarman in a Guppy-modded sub, and he knew hundreds of species by their creaks and clacks.

In WWII, active was the only game in town outside of very close ranges. And if there was weapon activity, such as the first DC, passive was even more useless.

I'd say anything outside of, say, 2000 yards, passive woudln't have gotten you any data in many cases, but that's a guess.

And this is the reason that US sub results REALLY suck when you use US doctrine: per Blair pre-war US doctrine was to use only passive on final approach for sub ATTACK. Per prewar training rules, any sub whose periscope was spotted by any surface or a/c combatent was automatically ruled as sunk. A couple of skippers who violated the rules and actually used the periscope to run an attack (in exercises) were relieved of command. You fight the way you train and the training was really, really bad for a pre-war sub skipper.

Most of the commanders apparantly realized that this was nonsense and used the periscope once it was a real war, but they had to hone their skills under combat conditions (with lousy torpedoes); however many of them did NOT change their tactics and stayed with passive attacks until relieved in 42-43 (again all per Blair)

[Dili]

I'd say anything outside of, say, 2000 yards, passive woudln't have gotten you any data in many cases, but that's a guess.

Yes but that range isn't different than active. For exemple US subchaser active sonars could not get more than 500yds and this in 1943, crew considered it almost useless. There wasn't any search active sonar in WW2 due to very narrow beam they were more attack sonars to be employed when a submarine was detected. What i want to know is how much that improved kill rates in first half of WW2. For example only with 144Q and 147Q late 1943 could depth be established, before that unless dozens of depth charges are set to explode at various depths. It is still better than passive only but how much better?

[rtrapasso]

ORIGINAL: Dili

I'd say anything outside of, say, 2000 yards, passive woudln't have gotten you any data in many cases, but that's a guess.

Yes but that range isn't different than active. For exemple US subchaser active sonars could not get more than 500yds and this in 1943, crew considered it almost useless. There wasn't any search active sonar in WW2 due to very narrow beam they were more attack sonars to be employed when a submarine was detected. What i want to know is how much that improved kill rates in first half of WW2. For example only with 144Q and 147Q late 1943 could depth be established, before that unless dozens of depth charges are set to explode at various depths. It is still better than passive only but how much better?

An interesting question, but i am not sure it can be answered with any accuracy... you might try comparing kill rates at the end of WWI (when ASDIC was just coming into play) vs. kill rates at the beginning of WWII (when active sonar was just coming into play)... that might give you a very ROUGH answer... at least for the Atlantic... and then you could assume that the results translated to the Pacific... of course, that assumption might not be valid, but it might give an answer good enough to play around with.

[Bullwinkle58]

ORIGINAL: Dili

I'd say anything outside of, say, 2000 yards, passive woudln't have gotten you any data in many cases, but that's a guess.

Yes but that range isn't different than active. For exemple US subchaser active sonars could not get more than 500yds and this in 1943, crew considered it almost useless. There wasn't any search active sonar in WW2 due to very narrow beam they were more attack sonars to be employed when a submarine was detected. What i want to know is how much that improved kill rates in first half of WW2. For example only with 144Q and 147Q late 1943 could depth be established, before that unless dozens of depth charges are set to explode at various depths. It is still better than passive only but how much better?

I don't think there's any way to isolate that one variable and assign a value to the delta in kill rates. There's too many other importnat variables of environment, depth, traiing, fatigue, etc. across the data set.

[Dili]

That is a good idea rtrapasso, but there is the problem that WW2 submarines got better. Anyway it could be a reference.

I don't think there's any way to isolate that one variable and assign a value to the delta in kill rates. There's too many other importnat variables of environment, depth, traiing, fatigue, etc. across the data set.

I don't think so, there are numbers for example Hedgehog Vs Depth charges in Royal Navy. In 1943 Hedgehog had 8% success while depth charge was 4-5%. I dont know how that was measured. Maybe i can just slap a success rate of 1-1,5%% and get done with it [:)]