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[Nisgeis]

The early war fleet boats with the WCA gear had four sonars underwater:

QC/JK - QC for echo ranging and the JK for passive listening. I believe the JK was ultrasonic and not so good for long distance (but quite good on bearing accuracy). Could not be used at the same time as they are mounted on the same head on reciprocal bearings.

QB - echo ranging with a wider frequency band than the QC

NM - Echo sounding equipment.


Note 'Q' is for a range projector/listener and 'J' is a passive listening device and 'N' is an echo sounding device (for depth).

They also had JP in the Forward Torpedo Room and the head was above the waterline and was in the sonic range. JT sonar, which was a later version had better bearing precision as it received both sonic and ultrasonic and a few extra features. Need to be submerged to use these.

EDIT: The sonar manual, advises the operator to continue listening when on the surface when conditions permit, e.g. weather and speed - as has been said previously water rushing over the sonar head drowns out other noise and also sea state plays a part too.

[Bilge_Rat]

Originally Posted by Stealhead

That sir makes absolutely no sense if the passive sonar head is above the water then there is no way on this earth that it is gong to be able to hear anything the same would apply to the S-boats all of the sound gear is on the deck so if you are on the surface and you can see the gear in the air then it can not possibly be in the water to enable it to hear anything the location of the gear 100% has an effect if said gear is on the deck on the surface and not in the water.In fact a sub on the surface trying to use sound gear which is above water will hear nothing.

I agree that there are limitations in the SH4 simulation but it makes perfect sense for a piece of sound gear not actually being submerged in the water not to be able to hear what might be in the water so the SH4 sound man is evidently Kent Clark and has super hearing.You seem to be confusing various things causing interference in a situation where the sound gear actually is in the water.I am talking about sound gear actually not being in the water and with US Navy subs the passive gear was above the water while the sub was on the surface but the active gear exluding the S-boats was below the water while surfaced.So active sonar while surfaced yes passive sonar no though I doubt the active sonar would be very accurate in such a setting.

well obviously I was not talking about sonar equipement which is outside the water, many fleet boats had their sonar heads located under the hull.

[Stealhead]

You did say location had no effect though which is not correct if that position was out of the water.Like wise when they went to the WCA set from the older QC/JK as on the S-boat there was some concern about use of the active heads while near the bottom which was not an issue with the QC/JK deck location.The WCA and later heads where retractable but it was not uncommon for them to get damaged anyway.The other thing to take into consideration is that the sub would have to be fully submerged to get full use of any one of the various systems to get an accurate picture using sonar they needed the full ensemble and there fore had to be completely submerged.

The sonar heads you mention are the active ones the ones that ping they are not the passive "hydrophone" type that allow you to listen to screws in the water.If you look at that link I posted you'll see that there where two active heads on the keel and one for sounding depth and the passive head is above the deck the JT head.

[Nisgeis]

JK is a passive hydrophone.

[Bilge_Rat]

Originally Posted by Stealhead

You did say location had no effect though which is not correct if that position was out of the water.

I presumed that I did not have to point out that a receiver in the air cannot hear noises under water, that is after all, pretty basic.

The sonar heads you mention are the active ones the ones that ping they are not the passive "hydrophone" type that allow you to listen to screws in the water.If you look at that link I posted you'll see that there where two active heads on the keel and one for sounding depth and the passive head is above the deck the JT head.

no, the JK/QC and QB heads located on the bottom of the hull are receivers.


http://www.hnsa.org/doc/fleetsub/sonar/chap5.htm

[joegrundman]

Interesting discussion TorpX (your part of it, anyway)

I'd been wondering about that very thing actually.

[Stealhead]

Originally Posted by Bilge_Rat

I presumed that I did not have to point out that a receiver in the air cannot hear noises under water, that is after all, pretty basic.





no, the JK/QC and QB heads located on the bottom of the hull are receivers.


http://www.hnsa.org/doc/fleetsub/sonar/chap5.htm

I am referring to the S-boats not the fleetboats on the S-boats the QC/JK is all mounted on the deck.If you would please view the 23rd 40th and 45th pictures on this link you will see a large transducer below it is a bar this is part of the system this is the JK/QC that you are trying to tell me is on the keel but not on any S-boat is not. http://pigboats.com/subs/s-boats4.html.







To be entirely honest I am getting different answers as to what is possible from different sources which makes me fell as though one cant say for certain what was possible but seesm that in order to get the full spectrum of passive sonic and supersonic sound gear the sub has to be completely submerged.In my onion this is a good question ask DaveyJ576 the most knowledgeable member on Subsim when it comes US Navy Sub technology this question What exactly was a WWII US Navy sub capable of dong with its sound gear on the surface and below for that matter? The problem with military technical manuals (I know from personal experience) is that can be overly optimistic and do not always represent what is done in the field for all we know the Chief of the boat may have tossed it overboard often they are written by engineers not by those actually using the gear in the field and truly knowing the in and outs.


Edit:
I did find on this HNSA page of US Navy Sonar; http://www.hnsa.org/doc/sonar/chap13.htm

"Submarine listening equipment is designed to receive and reproduce underwater sounds-both sonic and ultrasonic-for the purpose of identifying the sounds and locating their sources. Sonic sounds (below 15,000 cycles per second) are made by propellers, engines, rudder motors, pumps, gear wheels, and many other devices. Ultrasonic sounds originate mostly from high-speed propellers. The bearings of the sources of sounds usually can be determined, so that targets can be located without the use of echo-ranging gear.
The original J-series listening equipment was designed for use on submarines. Most modern listening equipment, such as the JP and JT, is designed for patrol craft, picket boats, and submarines. The JP-series listening equipment is now in use on submarines as a unit of the JT equipment."

To me this seems to say that we are both wrong/both right as one could use the part of the passive system but only the super sonic(which would now be called ultra sonic) side of the system would be usable on the surface and you would be unable to hear slower speed screws very well and the supersonic range was very short only a few thousand yards at best so you would only be getting half the picture on a good day.

[Bilge_Rat]

Stealhead,

We may be talking at cross purposes, I agree with you that a WW2 Fleet Boat would not be able to use its sonar on the surface, except in very limited ideal conditions.

[Stealhead]

Originally Posted by Bilge_Rat

Stealhead,

We may be talking at cross purposes, I agree with you that a WW2 Fleet Boat would not be able to use its sonar on the surface, except in very limited ideal conditions.

I was thinking this as well.I actually found a very interesting page on the HNSA site that has a whole mess of recordings of subs some of them are recordings of different ships screws and there is a sound recording from the conning tower of the USS Sealion as her crew attacks the IJN Kongo.

http://www.hnsa.org/sound/

[TorpX]

I found the relevent pages in O'Kane's book. I've quoted him at length because I consider him to be very knowlegable and so the reader can understand he put a good deal of thought into his strategy. This is from p54 of CLEAR THE BRIDGE, (I marked the most relevent parts in blue):



[QUOTE]... Dawn came and we continued our search, now augmented by the search periscope, with Tang still on the surface, lying to and maintaining quiet.

This was a far cry from accepted submarine doctrine, which dictated having way on the boat, but what is doctrine anyway? I believe it is a set of procdures, established through experience, that provides a guide. But doctrine should be flexible, never rigid, for circumstances often dictate complete departures. Our situation that day was an example of such curcumstances.

In order for us to utilize speed in searching, it was first necessary to know the general direction of the enemy's movement. We could then proceed on a very wide zigzag ahead and thus cover a broader front as the enemy overtook. But we were presently in an open-sea area, and enemy ships might be on any track, though the northwest-southeast courses passing through the western part seemed more likely. No amount of running around at our available speeds would increase the probability of sighting the enemy. In fact, to do so would only make us a target for a submerged enemy submarine and would blank out our sound gear with our own screw noises.

Tang was lying to in the center of a circle some 20 miles in diameter that we had searched by radar and sound during the three hours before daylight. It was clear of any enemy. The only planes that could reach our position were patrol bombers. We could sight them and dive before they sighted us, for our diving time when lying to was only five seconds longer than when proceeding at 15 knots. The only real danger was from a submarine, but she would first have to come into the area undetected by our sound, radar, scopes, and lookouts. Then she would have to conduct a many-mile submerged approach. This would call for considerable submerged speed. Our soundman, with no interference from our own propeller noises or from other machinery, would detect her screws before she reached an attack position. The foregoing was not just conjecture or we would not be staking our lives on it.

In addition, lying to while in this open-sea area would use only the diesel fuel necessary for normal living, just a fraction of that consumed when cuuising at one-engine speed. The oil we saved would be available when it might really be needed in persuing the enemy.

There were, of course, the alternatives of a submerged patrol with high periscope searches or of periodic surfacing. Neither of these would insure the coverage we wanted, nor would they save the fuel, as we would then be charging batteries nightly.

We shifed our patrol station 20 miles each evening so that if we were detected, shipping could not just be routed clear of a single spot. At the same time we were working south near the western boundary of our assigned area. ...
[/QUOTE]




From what O'Kane said, I think it is clear that he either worked out some of these search problems mathematically, or learned from intructors who did. Possibly, someone will find some USN charts/manuals/documents that deal with this issue.


From joe grundman:

Interesting discussion TorpX (your part of it, anyway)

I'd been wondering about that very thing actually.

Thanks.
I read OK's technique just as I started getting into subsims, and have used his tactics. I'm sure it is possible to have good patrols with other methods, but I still think OK's method is the best for searching in open-seas, where you have no assurance of finding plentiful contacts. I haven't read all the available literature by any means, but I believe at least a few others made use of similer strategies.