ASDIC and Destroyertactics

[Jaeger]

I made some testmission runs for understanding the DD AI. I am using the GWX 1.03, which is really good, but i think the AI is not balanced with my own sensors. I read lots of threads here, where they tried to configure visuell sighting distances and ASDIC. I think, there were very good results. ducimus, jungman Rubini and many more guys found out the way the AI works and made some good mods with new AI_sensors.dats. I like them very well, but there is still one problem, which seems to be hardcoded: if my sub is in the range of the activ sonar, the DD begins to ping, also if he cant know (my engines are switched off, dived to 180 meter), that there is a sub in the deep water. I searched the web for getting information about the asdic. in sh3, the destroyer normally uses only his passive sonar, and he begins to ping when the sub is in activ sonar range. he doesnt use his active sonar while escorting a convoy.

My question is: did they use their active sonar all the time in real life? And if so, how could they sleep when hearing the ping 24h a day? I cant believe that they used it all the day...

Annother explaination is supersonic. I heard about supersonic waves, which were emitted by the active sonar all the time, so the sonar operator gets a hint, when its time to begin with sending pings. this would explain why the DD in sh3 begins to ping when a sub enters his active sonar range. Where can i get information about asdic development and about tactics in convoyescorting? (in the web) and second: did somebody hear anything about supersonic waves, which were emitted all day long?

thanks for your help

[Von Manteuffel]

There was no set operational procedure to determine when escorts used active Sonar (pinging), or settled for passive listening devices (hydrophones). Basically, escorts carried out three distinct ASW roles:

1. Hunt - Seek to find as many enemy submarines as possible with little, or no knowledge as to their previous locations. ( e.g. an escort commander passing through a known U-Boat "hot zone" would constantly scan the underwater environment with hydropphones and/or pings, assuming that U-Boats were present. ) "Hunting" involved using the sonar on a broad band setting to cover as much area as possible. Obviously, the probability of a ping returning an echo from a target depended on the distance and how often the escort sent out a searching ping.

2. Location - establish the position of a U-boat whose position has been reasonably accurately determined. ( e.g. an escort would go into location mode once a periscope had been spotted, or following a torpedo attack, when the direction (bearing) from which the torpedoes had been launched could be determined. ) This used a narrower Sonar beam and continuous pinging.

3. Screen - 1 & 2 are Offensive tactics, Screening is defensive and tried to establish a zone through which any enemy submarine making an attack would have to pass. Again, a broad Sonar Band was utilised. Screening was most effective when several escort vessels combined to overlap their detection areas ( e.g. to cover the area ahead and abeam of a convoy, giving almost instantaneous triangulation )

For 1 & 3, often passive listening via hydrophones and well-trained operators was used, supplemented by periods of searching with active Sonar.

Often the actual ping was not heard by the operators etc, as they could shut down that part of the system which let them hear the transmitter and listen purely for echoes.

Operationally, depending on the skill of the operator(s) WW II Sonar could determine the bearing and range of a submerged target. Analysis of the Doppler effect could also give the change in course, or bearing of the target submarine. The problem was in establishing the target submarine's depth. This was largely down to guesswork, based upon the point at which the submarine passed under the Sonar beam. This "dead zone" could extend to as much as 600 meters. Hence, until depth-finding equipment was introduced ( late in the War by the U.S. ) the practice was to saturate an area with depth-charges, rather than try for an "aimed hit."

Ultrasonic listening devices and transducers were used. They were, size, for size, considered more accurate than normal Sonar - especially in determining a target's bearing - , but they still relied on heterodyning to transform an inaudible ultrasonic signal into something an operator could hear and analyse.

Given all the variables due to refraction, salinity, temperature, the different probability of detection patterns given by different transducers etc etc. the detection of underwater targets by sound, either active, or passive, was one of the most skilled and difficult tasks undertaken by surface vessels.

[Jaeger]

thanks for aour long statement. here we can see, that the KI in SH3 cheats. the dived sub with engines stopped is detected by a destroyer, which is screening, when the sub enters his activ sonar range. you wrote, that they didnt ping while in normal screen mode, so how they can know that its time to ping? i think the game gives them information about the subs presence, though their sensors cant mesure this presence...

This happened to me either. Even with the silent mode switched on and at full stop at periscope depth escorts are usually lucky to spot a submerged u-boat.. They might have got a sixth sense about where u're at u know

[Von Manteuffel]

What I was trying to explain was that whether a sub pinged, or not depended on the amount of threat the escort commanders believed there to be. It would also depend on the preference of the individual escort commanders. Some would ping for a huge amount of a voyage - even when screening. Others only when they felt that there was a real chance that a U-Boat was in the area. The skill of the hydrophone operators, who listened for and identified underwater sounds passively would also effect which method of detection was favoured.

The detection model in SH 3 is rather basic. It doesn't seem to take into account the very commonly used practice of pinging at 5-degree intervals and not transmitting the next ping until there was a "negative echo" from the previous one.

The average speed of sound in sea water is around 1500 metres per second, although it differs with temperature and salinity. The maximum range of an Asdic, or Sonar system depended on a great many factors, but was never more than 3,500 metres, so to ping and wait for an echo until a "negative" was recorded would take 4.7 ( say 5 seconds ). Add to this the time to move the transmitter through 5 degrees of arc ready for the next Ping, say another 3 to 5 seconds, and you have a "ping" every 8 to 10 seconds.

To cover the full 180-degree sweep ( from red 90 to Green 90 ) takes 36 pings at 5 - degree intervals, or between 5 and 6 minutes. To get back to the starting point of red 90 takes the same. So, a ping went down a 5 degree arc once every 10 minutes, or so. So, sweeping with Sonar was, perhaps, not a very sure, or efficient way of detecting submerged targets.

Sometimes, pinging was used simply to alert submarines to the fact that the hunters were around and ready for trouble. If a submarine commander heard a ping, he would be very foolhardy not to react to the threat of detection by slowing down, reducing the noise made by his boat and, or diving deep. All these actions reduced his effectiveness and opportunity to launch a successful torpedo attack.

I don't think the escorts' AI cheats. I think it simply isn't sophisticated enough to model real-life better than it does. This isn't surprising since their were so many variables involved and a computer game - which this is - has to make a great many compromises.

I am surprised at the number of people who seem to want to tweak the escorts AI to make them tougher ( i.e. make their powers of detection stronger ) which IMHO is non-realistic, but a game in which the chances of detection were realistic and, perhaps, in which a hunter would sit over a sub's position for 12 hours , or more, wouldn't be a great deal of fun to play - except for the total "absolute realism" buffs.

[Drago79]

Hello
I have a question how to create an asdic for my destroyer. Can it even be done. Where do I start. With I was building a destroyer. I do not know how to allocate asdic. How to set sonars and hydrophore to detect u-boat

[Hooston]

ASDIC for a hedgehog attack. Mindbogglingly complicated, needs a lot of people who know exactly what they are doing.

https://www.dailymotion.com/video/x7qjuo7

I'm sure it also took real grit to stay awake all the way through the training film.

I've found a good overview of escort tactics here:
https://kclpure.kcl.ac.uk/portal/fil...317/408475.pdf


initially the RN had a hopelessly optimistic view of ASDIC effectiveness. Later they recognised that only a minority of attacking uboats would be detected before launching torpedoes because of the system's short range compared to the size of a convoy and the inherent unreliability of the process. However ASDIC remained the basis of the convoy screening diagrams and so escorts could be expected to ping more or less continually. SH3 only lets the player hear a ping at close to the threshold of detection, so it's hard to say what the escort is using. For sure the escorts do not ping at all for a lot of the time in game. Overall the percentage of times it is possible to penetrate the screen undetected underwater seems about right, although maybe not for the right reasons.

SH3 depth charges seem to be very well aimed with regard to depth, when in reality the escorts would be forced to bracket a huge range of depths. This can be used by the SH3 player as a radical change in depth will almost always result in a miss. On the other hand extreme depth is not a sure fire protection in game, when in real life maximum depth charge settings were always a good deal less than the 200m+ boats could go to. On the other other hand the escorts clear off after less than an hour when the late war real life advice was 24 hours!
So there's a LOT wrong with SH3 as a simulation, yet thanks to years of work by modders it still holds up against the competition and still captures the "feel" perfectly.