Fire Control Systems in WWII
Let me start by suggesting a revisit to our friends at the "Baddest" website, specifically in the subject of Fire Control:
The above is a good capsule summary of the FCS of the major battleships of each nation and I'm going to refer to it in this post. For purposes of simplicity, I am only going to discuss the British, German, Japanese and US ships. Since you are only interested in optical FC, I'm also not going to discuss radar FC except to state, once again, that radar FC beats optical in almost any situation and so there's little point in comparing the two.
Now, three points to note:
The British battleships lacked RPC almost entirely until late in the war. The Japanese never implemented it in any meaningful way. The Germans had it only for elevation (more on that later) while the USN had it for both elevation and bearing. To me, RPC is one of the single most important advancements in the development of accurate gunnery. No longer did the director operator shout down a voice tube "target bearing 230 degrees at 20,500 yards" to which another sailor dialed into the rangekeeper (analog computer) which was then transmitted to a set of dials in the gun mounts which then the gun captain had his trainers and elevators match by slewing/elevating the guns to match the dials, with at every point a potential for operator errors. Instead, the director operator now controlled the laying of the guns almost directly. Plus, in the US system, there was a feedback system where the rangekeeper moved the director sights to where it thought the ship should be shooting. If it wasn't correct, the director operator adjusted the sights back on target, thus setting up a closed-loop system (for a living, I design process control computers that do this digitally. So, please trust me on this, I'm amazed at what was achieved in closed-loop systems using 1930s analog computers). The German system had RPC only for the elevation, but this is not as bad as it may seem. Since, in the German system of "bracket salvos," the first half salvo is really to determine bearing, they did not feel that the extra complication was necessary. Judging from the results at River Plate and Denmark Strait, it's hard to argue, but, my personal opinion is that it would have been worth the investment. The Japanese, as in much of their naval technology, used the same methodology as their British mentors and used a "follow the pointer" system for both elevation and training.
The main director baselength on the Japanese, German and US ships was roughly about as long as on the main turrets and was relatively large. By contrast, the British had a relatively short baselength both as compared to the turret rangefinders and as compared to those of other nation's ships. In fact, the main director on British ships was almost an afterthought, intended to be used more for fire direction than for fire control. The real FC rangefinders in the British ships were the ones on the main turrets. Again, I was surprised when I discovered this a couple of years ago, as the British pioneered centralized FC and the Nelson class with their high-mounted directors greatly influenced subsequent designs. The British reliance on turret RF's is really a holdover from pre- and early-dreadnought days, where each individual turret layed the guns for themselves.
This reliance on turret RF was shown flawed at the Denmark Strait: Since Adm. Holland chose to push his ships directly towards the Germans and thus into the wind; sea spray coated the optics on all four forward turrets and forced the British to use the less accurate main directors. I think that the results speak for themselves: The British fired long-spaced ladder salvos and didn't land a hit until after the POW turned broadside to the Germans (i.e., the turrets no longer faced into the sea spray) at a relatively short range of about 16,000 yards. As a result of this engagement, the British belatedly realized their design/concept flaw and installed a larger (but still relatively short) baselength director on the last three KGV ships. However, only the forward director was modified, the aft director was unchanged.
The use of stable vertical elements in the US systems. I call your attention to the paragraph at the bottom of the above "Baddest" link, describing the performance of the USS North Carolina (the oldest of the new battleships) during a series of maneuvers where she still maintained target lock. Since you own "British Battleships," I won't repeat the problems and successes that the British had with their systems. I have only limited information on what other nation's ships were capable of, but it appears that the German's systems were at least equivalent to those of the British (I assume this from descriptions in Whitley's and Campbell's books plus Baron Mullenheim-Rechburg's comments in "Survivor").
Bottom line: The Japanese and the Germans had better optical RF's than any other nation. In a fight where only optical systems are used, they had a clear advantage as shown at Denmark Strait, the River Platte and First Savo (I assume that you've seen my previous posts regarding the POW's radar and won't revisit the subject). However, the US had the best FC as a system (FCS). What this meant is that, when 10cm fire-control radar became available, the US was able to easily integrate it into their FCS, thus creating the best overall FCS as compared to the FCS used by any other nation. My (strictly amateur) conclusion is that the US FCS with radar was the most advanced of any nation in the 1942-1945 timeframe.
One other item, per your last post: I do not take the Bismarck's performance at her last battle as being truly indicative of her performance. The crew was exhausted by their night-long skirmishing with Capt. Vian's destroyers and the Bismarck's motion was subject to random direction changes. By contrast, the British battleships had rested crews firing from stable platforms. As always, I dislike to speculate upon "what-ifs," especially this one, as, in my opinion, an undamaged Bismarck with Adm. Lutjens in command wouldn't have fought against the KGV and Rodney, she would have beat feet in the opposite direction as fast as possible. So, I'll leave any thought as to what the outcome of an engagement between healthy ships to others.
I originally did this as a response to a question on one of our Bulletin Boards. It remains in that format, pending my finding some time to rewrite it.
- 17 April 2001