Bismarck 150mm fire control

[alecsandros]

Hello,

Following a discussion on another board,
I would like to ask you how were the 150mm turrets normaly controlled ? Did they receive directions from the main fire control directors, did they use their own rangefinders, or from the 105mm directors perhaps ?
I suppose all 3 ways were possible, but I am interested in the way they were normaly expected to function.

Thanks,

[Thorsten Wahl]

By C 38 firecontrol computer within the plotting rooms.
range and bearing data wer provided by all range keepers including(including night range keepers and AA range keepers), target diposers and radar equipment.

any measuring equipment could be switched (alone or in groups) on any firecontrolcomputer and any fire controlcomputer could be switched on any turret(main and secondary artillery)

[Steve Crandell]

By C 38 firecontrol computer within the plotting rooms.
range and bearing data wer provided by all range keepers including(including night range keepers and AA range keepers), target diposers and radar equipment.

any measuring equipment could be switched (alone or in groups) on any firecontrolcomputer and any fire controlcomputer could be switched on any turret(main and secondary artillery)

You can't be saying that 15cm computers could compute trajectories for 38cm guns. Completely different ballistics. Probably unnecessary anyway since each caliber gun had it's own computer(s).

With respect to directors, I believe that the Baron describes the 15cm battery being normally controlled by the gunnery officer in the conning tower. Did the secondary battery have it's own dedicated directors? I can't find any reference to them. They would of course use their own rangefinders in addition to any others connected to the circuit. Rangefinders are a whole separate category from directors, especially in the German case, where they had main battery range finder copulas separate from the associated directors, which were below them.

[Thorsten Wahl]

C 38 doesnt mean Computer for 38 cm SK C/34, meaning of [C 38] is construction date
the ballistics could be replaced
Nevertheless ther are four C 38 on Board two in each Plotting room.
additional there are two C 38 wich had ballistics for star shell

the Hippers also had [C 38] Computers and also the modern destroyers had these [C 38 Z]

[Steve Crandell]

C 38 doesnt mean Computer for 38 cm SK C/34, meaning of [C 38] is construction date
the ballistics could be replaced
Nevertheless ther are four C 38 on Board two in each Plotting room.
additional there are two C 38 wich had ballistics for star shell

the Hippers also had [C 38] Computers and also the modern destroyers had these [C 38 Z]

I was not connecting C38 with 38cm guns. I was asking if C38 computers were capable of computing solutions for main battery guns. Are you saying that the ballistics cams in the C 38 computers could be replaced with 38cm cams while in action? On USN ships I don't think there were even 16" cams available for Mark 37 computers and in any case it might be a yard level change. The Mark 37 directors could be used to control 16" guns, but they would be connected to one of the main battery fire control computers, not a secondary battery computer.

[alecsandros]

@Thorsten
Thanks ,
Still I do not understand how were the correction made. The firing solution was calculated in the plotting rooms and sent back to the turrets/guns. But who/where was normally making the spotting of fall of shot, and who was sending the new observations "downstairs" to the plotting rooms ?

If the salvos were 500m short of the target, who/where anounced this ?

[tommy303]

I was not connecting C38 with 38cm guns. I was asking if C38 computers were capable of computing solutions for main battery guns. Are you saying that the ballistics cams in the C 38 computers could be replaced with 38cm cams while in action? On USN ships I don't think there were even 16" cams available for Mark 37 computers and in any case it might be a yard level change. The Mark 37 directors could be used to control 16" guns, but they would be connected to one of the main battery fire control computers, not a secondary battery computer.

Each plotting room had a separate Schusswertrechner or computer, one for the main battery and one for the secondary battery. Topside, the gun directors could be used for either main or secondary armament. Control of the secondary armament was normally exercised from the forward artillery command post in the conning tower, while the foretop post was the normal control position for the main armament. Each of these had three directors and one rangefinder cupola, as well as spotting periscopes to observe and correct fall of shot. The after command post was a reserve in case either the 38cm or 15cm control positions forward were disabled or unable to follow the target. It could also be used should it be convenient or expedient to divide the fire of one battery against a second target.

[Steve Crandell]

I was not connecting C38 with 38cm guns. I was asking if C38 computers were capable of computing solutions for main battery guns. Are you saying that the ballistics cams in the C 38 computers could be replaced with 38cm cams while in action? On USN ships I don't think there were even 16" cams available for Mark 37 computers and in any case it might be a yard level change. The Mark 37 directors could be used to control 16" guns, but they would be connected to one of the main battery fire control computers, not a secondary battery computer.

Each plotting room had a separate Schusswertrechner or computer, one for the main battery and one for the secondary battery. Topside, the gun directors could be used for either main or secondary armament. Control of the secondary armament was normally exercised from the forward artillery command post in the conning tower, while the foretop post was the normal control position for the main armament. Each of these had three directors and one rangefinder cupola, as well as spotting periscopes to observe and correct fall of shot. The after command post was a reserve in case either the 38cm or 15cm control positions forward were disabled or unable to follow the target. It could also be used should it be convenient or expedient to divide the fire of one battery against a second target.

There were periscopes separate from the directors? I don't think I've seen those on models or photos.

[Matrose71]

Each plotting room had a separate Schusswertrechner or computer, one for the main battery and one for the secondary battery.

This is correct, but also incorrect. Each computer was a C 38 (2 for every plotting room) and they were interchangeable for the main and/or secondary battery.
Each C 38 could perform with the main or secondary battery.

Still I do not understand how were the correction made. The firing solution was calculated in the plotting rooms and sent back to the turrets/guns. But who/where was normally making the spotting of fall of shot, and who was sending the new observations "downstairs" to the plotting rooms ?

If the salvos were 500m short of the target, who/where anounced this ?

As Thorsten wrote in post 2

range and bearing data wer provided by all range keepers including(including night range keepers and AA range keepers), target diposers and radar equipment.

any measuring equipment could be switched (alone or in groups) on any firecontrolcomputer and any fire controlcomputer could be switched on any turret(main and secondary artillery)

[Steve Crandell]

OK, my next question is:

If there is all this redundancy and all these tertiary directors and rangfinders can control Bismarck's main battery, why didn't they do so after the Baron's position was disabled? He states in the book that after the hit which disabled all of the directors in his position, there was no longer any central control for the main battery.

It appears to me that most of this redundancy was only theoretical. The Baron obviously didn't even consider trying to transfer control to an AA director or anywhere else.

[alecsandros]

OK, my next question is:

If there is all this redundancy and all these tertiary directors and rangfinders can control Bismarck's main battery, why didn't they do so after the Baron's position was disabled? He states in the book that after the hit which disabled all of the directors in his position, there was no longer any central control for the main battery.

It appears to me that most of this redundancy was only theoretical. The Baron obviously didn't even consider trying to transfer control to an AA director or anywhere else.

... They still had rangefinders on board and could calculate fire control solutions, but they did not have a spotting/comand position anymore, as both forward command posts had been taken out, and later the aft one also. So they would be firing in the blind... somwehat...

So they did fire, but badly.
Also, the rangefinders which were still functional by 9:20 were either located to low in the ship (such as the 10,5m rangefinders of the main turrets) or were simply to small to provide accurate ranges at long distances. The 4m rangefinders of the 105mm guns were probably not up to the task of accurately ranging KGV at 12km away. They were also not located so high within the ship as to provide a good field of view.

[Steve Crandell]

OK, my next question is:

If there is all this redundancy and all these tertiary directors and rangfinders can control Bismarck's main battery, why didn't they do so after the Baron's position was disabled? He states in the book that after the hit which disabled all of the directors in his position, there was no longer any central control for the main battery.

It appears to me that most of this redundancy was only theoretical. The Baron obviously didn't even consider trying to transfer control to an AA director or anywhere else.

... They still had rangefinders on board and could calculate fire control solutions, but they did not have a spotting/comand position anymore, as both forward command posts had been taken out, and later the aft one also. So they would be firing in the blind... somwehat...

So they did fire, but badly.
Also, the rangefinders which were still functional by 9:20 were either located to low in the ship (such as the 10,5m rangefinders of the main turrets) or were simply to small to provide accurate ranges at long distances. The 4m rangefinders of the 105mm guns were probably not up to the task of accurately ranging KGV at 12km away. They were also not located so high within the ship as to provide a good field of view.

According to others, the 4.1" AA directors could have been used for spotting the main battery. I don't know, but I would estimate they were about 50 feet off the water. But they weren't used. Apparently no one tried to use them. Where is the redundancy you are referring to? All I see is three main fire control positions, which is fine but you and others have claimed there were many more than that which could have been used to control the main battery.

With respect to range finders, the C turret range finder was extremely accurate and was high enough in the ship to see KGV. Maybe not high enough to spot shell splashes effectively, but high enough to obtain ranges.

[alecsandros]

All I see is three main fire control positions, which is fine but you and others have claimed there were many more than that which could have been used to control the main battery.

With respect to range finders, the C turret range finder was extremely accurate and was high enough in the ship to see KGV. Maybe not high enough to spot shell splashes effectively, but high enough to obtain ranges.

... No one said there were more than 3, just that fire control solutions could still be calculated downstairs based on the inputs from other measuring instruments... And Bismarck had 12 rangefinders capable, in various degrees, to measure range to enemy ships. But the best one was the foretop one... 10.5m baselength with 31.5meters altitude... great field of view...

We do not know if they tried to use a 105mm director in the final minutes... who knows... were they still operational at least at 9:20 ?

[Steve Crandell]

All I see is three main fire control positions, which is fine but you and others have claimed there were many more than that which could have been used to control the main battery.

With respect to range finders, the C turret range finder was extremely accurate and was high enough in the ship to see KGV. Maybe not high enough to spot shell splashes effectively, but high enough to obtain ranges.

... No one said there were more than 3, just that fire control solutions could still be calculated downstairs based on the inputs from other measuring instruments... And Bismarck had 12 rangefinders capable, in various degrees, to measure range to enemy ships. But the best one was the foretop one... 10.5m baselength with 31.5meters altitude... great field of view...

We do not know if they tried to use a 105mm director in the final minutes... who knows... were they still operational at least at 9:20 ?

If the main battery directors are disabled it doesn't really matter how many rangefinders you have left. You no longer have centralized control of the main battery.

[Thorsten Wahl]

I was asking if C38 computers were capable of computing solutions for main battery guns. Are you saying that the ballistics cams in the C 38 computers could be replaced with 38cm cams while in action?

I took a look in the service regulation for weapon systems on board Bismarck class (TS131 - 22065 - B.B.V.-W- - Bauvorschrift für die Waffenanlagen),it state that ther were two C38 within each plotting room one associated to the main artillery and one associated to secondaries.

My additional information came from Paul Schmalenbach (History of german naval artillery), who state that ballistic cams were generally interchangeable.