Bismarck and her contemporaries

[alecsandros]

Steve, I doubt anyone here doesn't believe that hits beyond 30km were possible, especialy late in the war. As you said, it's common sense.
The problem, at least in my case, is the expected probability of hits with regards to the external factors - atmosphere, air pressure, magnetic field in the region, waves, snow, etc...

For instance, in a battle in the Arctic, 1944, Asuming Tirpitz vs Massachussets, 30km away, sea condition - poor, gale force 10. Weather - snow storm.

is it sensible to expect a 3% hit probability from either ship using RDFC ? or 2% ? or 0% ? After all, Duke of York scored 10 shots at the most against Scharnhorst (out of 446 fired!), and that from 10-19km away... Of course, it wasn't the "end it all" radar that the US Navy used in late 1944, but still...

===

And, let's say we come to a solution for this problem. But what about the other possible encounters? How probable was that Alabama would hit Mutsu at 32km away, at night, moderate sea, powerfull air currents in the lower stratosphere?

What I'm trying to say is that we can only come to terms when the external factors mentioned above are very slim or non-existent. So, in good sea, good weather...

[Bgile]

Steve, I doubt anyone here doesn't believe that hits beyond 30km were possible, especialy late in the war. As you said, it's common sense.
The problem, at least in my case, is the expected probability of hits with regards to the external factors - atmosphere, air pressure, magnetic field in the region, waves, snow, etc...

For instance, in a battle in the Arctic, 1944, Asuming Tirpitz vs Massachussets, 30km away, sea condition - poor, gale force 10. Weather - snow storm.

is it sensible to expect a 3% hit probability from either ship using RDFC ? or 2% ? or 0% ? After all, Duke of York scored 10 shots at the most against Scharnhorst (out of 446 fired!), and that from 10-19km away... Of course, it wasn't the "end it all" radar that the US Navy used in late 1944, but still...

===

And, let's say we come to a solution for this problem. But what about the other possible encounters? How probable was that Alabama would hit Mutsu at 32km away, at night, moderate sea, powerfull air currents in the lower stratosphere?

What I'm trying to say is that we can only come to terms when the external factors mentioned above are very slim or non-existent. So, in good sea, good weather...

I agree that there are a lot of external factors that can screw things up, and I don't have any idea what sort of hit probabilities one could assign to the gale conditions you describe. Pretty poor, I'd imagine. I doubt you are going to be shooting at each other at 30km or even 25 km. In that kind of weather, but admittedly I just don't know. US battleships might suffer from North Atlantic gales more than Tirpitz as well. Smaller ship and I think less freeboard.

[lwd]

In those conditions I'm not sure how the radar antanna's would hold up. In Renown vs the twins both had trouble with their ordinance because of the seas. In such a battle flotation hits would also become more important. In an engagement such as this other conditions such as what both sides are trying to do become even more important. Although if we get into that discussion I don't see much chance we'd ever see a one on one duel between a US fast BB and a Bismrack. The US didn't tend to send out battleships by themselves.

One of the advantages some attribute to US battleships is the "stable verticle elements". This apparently allowed them to maneuver and maintain a good fire control solution. Would this become even more important in the case above or is it irrelevant?

[Bgile]

In those conditions I'm not sure how the radar antanna's would hold up. In Renown vs the twins both had trouble with their ordinance because of the seas. In such a battle flotation hits would also become more important. In an engagement such as this other conditions such as what both sides are trying to do become even more important. Although if we get into that discussion I don't see much chance we'd ever see a one on one duel between a US fast BB and a Bismrack. The US didn't tend to send out battleships by themselves.

One of the advantages some attribute to US battleships is the "stable verticle elements". This apparently allowed them to maneuver and maintain a good fire control solution. Would this become even more important in the case above or is it irrelevant?

I don't know, but I think stable vertical has more to do with free maneuvering while shooting. The USN apparently continued to work on this device as the war progressed. It works best in conjuction with complete RPC for guns and turrets.

[tommy303]

One of the advantages some attribute to US battleships is the "stable verticle elements". This apparently allowed them to maneuver and maintain a good fire control solution. Would this become even more important in the case above or is it irrelevant?

The German fire control system was very similar to the USN and just as capable. In extremely rough weather, with severe pitching and rolling, neither would be able to use the continuous aim feature and would have to fall back on locking the guns on the required elevation and wait for the gyro system to fire on the up roll as the ship came level.

[Bgile]

One of the advantages some attribute to US battleships is the "stable verticle elements". This apparently allowed them to maneuver and maintain a good fire control solution. Would this become even more important in the case above or is it irrelevant?

The German fire control system was very similar to the USN and just as capable. In extremely rough weather, with severe pitching and rolling, neither would be able to use the continuous aim feature and would have to fall back on locking the guns on the required elevation and wait for the gyro system to fire on the up roll as the ship came level.

I thought the German system didn't use RPC in one of the axes and instead used "follow the pointer" in either elevation or traverse. Also, it wasn't until several years into the war that the US system was able to follow the target through a complete circle of own ship. Do we know whether the Germans updated theirs as the war progressed? I suppose so, but to we know?

[lwd]

From what I read the system was capable of it from a fairly early date but it was post war testing that showed the capability to maintain a lock through more than 360 degree turns. I thought that some of the same sort of factors might apply to being knocked around by storms as apply to course changes. This is not an area however where I claim any expertise.

[Bgile]

From what I read the system was capable of it from a fairly early date but it was post war testing that showed the capability to maintain a lock through more than 360 degree turns. I thought that some of the same sort of factors might apply to being knocked around by storms as apply to course changes. This is not an area however where I claim any expertise.

One thing which may or may not be of importance in a heavy sea ... US elevation rate was 12 deg/sec, while the German one was half that. That might relate to being able to keep the guns on the proper elevation and might effect rate of fire. I don't know how if Bismarck would roll faster than 6 deg/sec.

[Bgile]

From navweaps:

"6) RPC was fitted for elevation but not for training. This elevation control was considered to be unsatisfactory in Bismarck."

[tommy303]

Hi Steve,

I thought the German system didn't use RPC in one of the axes and instead used "follow the pointer" in either elevation or traverse.

True, in their battleships, remote power control was installed either for elevation or traverse, but not both, whereas in the newest USN battleships RPC was applied for both. To a degree, the automation provided by remote power control was a desirable and worthwhile refinement, as it simplified the task of continuous aim, but was not an absolute necessity and even in ships with RPC, follow the pointer systems were retained as back up. A good many cruisers and battleships built prior to the 1930s did not have RPC at all and did some fine shooting without it. As far as I know, Vanguard was the first RN battleship to have RPC for its main armament, all the rest, including the older USN ships, and navies of Japan, Italy and France used the old follow the pointer throughout the war.

The German RPC system was based on thyratron power amplification, while the US system used servos. Both required generous amounts of AC power. However, RPC was not an absolute necessity when it came to continuous aim during manouvers, and could not in any event cope with really rapid changes of direction or severe rolling due to gale force winds because the changes in course or velocity of roll might at times exceed the traverse or elevations speeds of the mounts and guns. In such instances one simply locked the guns in either elevation or train and fired when the gyro system closed the firing circuits at the proper time.

[dunmunro]

AFAIK, Washington did not use RPC against Kirishima. The USN also had problems with servo backlash with their RPC systems which caused some loss of pointing accuracy.

S&G had problems with water entering the main armament turrets and shorting out FC systems, whereas PoW's A turret, which also got wet, did not suffer similar problems.

[Bgile]

AFAIK, Washington did not use RPC against Kirishima. The USN also had problems with servo backlash with their RPC systems which caused some loss of pointing accuracy.

S&G had problems with water entering the main armament turrets and shorting out FC systems, whereas PoW's A turret, which also got wet, did not suffer similar problems.

Do you have any info about problems with servo backlash with Main battery control? I thought that was just for the 5"/38 with it's very high traverse rate and that it tended to "hunt". As far as I was aware the main battery guns and turrets are too heavy for that to be a problem.

[dunmunro]

AFAIK, Washington did not use RPC against Kirishima. The USN also had problems with servo backlash with their RPC systems which caused some loss of pointing accuracy.

S&G had problems with water entering the main armament turrets and shorting out FC systems, whereas PoW's A turret, which also got wet, did not suffer similar problems.

Do you have any info about problems with servo backlash with Main battery control? I thought that was just for the 5"/38 with it's very high traverse rate and that it tended to "hunt". As far as I was aware the main battery guns and turrets are too heavy for that to be a problem.

I can't locate anything right now but the fact that Washington did not use RPC in late 1942, tends to make me think that there were problems with it. Unfortunately when I was in the USN Library in DC, I didn't gather much material on main armament RPC.

[Thorsten Wahl]

I thought the German system didn't use RPC in one of the axes and instead used "follow the pointer" in either elevation or traverse.

you are mixing different aiming and firing procedures

the german capital ships use the following aiming and firing procedures
1)
main procedure
RPC for elevation - Seitenvorzündwerk (i dont know a correct translation)
Seitenvorzündwerk means a gun only shots, when it occupies the correct direction the shoot value calculator pretends.
on the command durch(through) the complete turret will be moved through this correct direction and the shoots will be automatically triggered
so even the ships turns in direction the correct aiming direction was hold
the shoot value calculator/ gyro stabilisation /RPC was able to correct both for rolling up to 15 degs and it also includes various corrections for example for jam (verkanten), wind and V0-correction, parallax correction, the data were separately calculated for every turret and overlayed in the RPC/Seitenvorzündwerk

the calculator differenciates between own share and enemy share of change of distance and suspension(Vorhalt).
so even a 360 deg turn was not a problem for continuous firings

all bearing and distance data were delivered by automatic input from all optical range and direction finders (for mean),
through a separate switching it was able to use Funkmess data for range. the technical specifications of the Seetakt calais indicates that is was also able to deliver bearing data by the Feinpeileinrichtung

by 1943 it was possible to use a Wärmepeilgerät(Bolometer) for bearing (accuracy 0,1 degs which is similar to the optical rangfinder)
The funkmess/Bolometer combination was succesful testet on board of Prinz Eugen at distances between 14-18km in night shooting trails including 360 deg turns

at the end of the automated calculation the operator was able to override every setting

the AVKS Bismarck reports states oszillations at the barrels when RPC was on , but this was solved and at the end SKL was very satisfied with the accuracy of Bismarcks and Tirpitz shootings
the summer 1941 baltic trials of Tirpitz against the maneuvering targetship Hessen show the ability to aim and hit remote targets at 25 km. photos indicates that dispersion was very low (a Photo shows two simultan impacts less then 100 m from each other)

2)
ancillary procedure
aiming with follow pointer method with central firing and/or Zentralvorzündwerk for roll and pitch(Krag-Krängungsabfeuerungsgerät)

3)
reserve procedure
direct elevation and direction angle-turret firing

[Dave Saxton]

Thank's for posting these vitally important findings and insights Thorsten.

the technical specifications of the Seetakt calais indicates that is was also able to deliver bearing data by the Feinpeileinrichtung

The bearing accuracy attained by the Calias B Seetakt using Radattel-Peilung lobe switching was within 1/10 of a degree. However, this capability wasn't generally available aboard the large warships until a remedy to the bearing inaccuracies inherent to the traversable range finder mountings was put in effect by approximately mid to late 1941-early 1942.

through a separate switching it was able to use Funkmess data for range.

The range to target metric of the radar systems, which was electronically and continuosly measured by the radar operator holding the selected target pip on the null mark at the center of the fine range CRT screen, was automatically transmitted to the central fire control via selsyns. Using Funkmess as the primary method of measuring range to target was a no brainer, because of Seetakt's remarkable range accuracy when using it's fine range system, which was progressively improved. The Hipper's exceptional radar directed shooting and innovative shooting methods in late 1942 certainly attest to this.