US Navy Fire Control Systems - How They Really Work

Today we take a look at the ridiculous complexity of the USN's WW2 battleship fire control systems with the help of internationally known expert Dr Scholes!

[vikkimcdonough]

1:11:11

*Battleship **_Texas_** Fire Control:* "Hurry up with the abacus! Chief Wardzynski needs to carve the solution into his clay tablets!"

[SlinkyTWF]

A friend's father was an ensign aboard a Gearing class DD near the end of WWII. They were testing a new fire control computer prototype on a deserted island near Cuba one day. Unfortunately, there was a bug in the computer. Instead of averaging the rangefinder results, the computer added them together. They missed the island. Thank goodness for QA...

[michaelsnyder]

(Fire Control Part 3) Capital ships with two directors and two plotting rooms, each with its own computer, could engage two targets. The US “fast” battleships had a switchboard in their plotting rooms that allowed any director to use any mount, so that one main gun turret could be controlled by each Mk.38 director and one by one of the secondary Mk.37 directors. In this case, the Mk.37 director would by-pass its own computer to synchronize with the main armament plotting room. Some capital ships had an emergency control director in the rear of a turret (usually a super-firing turret farther above the waterline) with a simplified computer to provide director control to the gun turrets. Each mount, of course, could engage targets in local control, some navies fitting simple fire control computers at the turret officer’s station to generate a firing solution. All of this was controlled by the ship’s gunnery officer. Positioned in the conning tower or on the bridge, the gunnery officer usually had a target indicator, binoculars on a pedestal or a periscope that might communicate bearing automatically or manually. Often the gunnery officer had a spotting glass or even a rangefinder. Sometimes there was even a simplified fire control computer at his station as a backup. Modern US “fast” battleships had two primary and six secondary directors for the main armament. A spotting glass was different from a rangefinder. The spotting glass was used to detect the fall of shells and their distance from the target, not the distance from the firing ship to the target. The USN used spotting glasses in some directors, with the Mk.34 initially having a spotting glass, which was replaced from 1940 with a 15’ stereo rangefinder.
All these improvements still operated within the physical limit of the visual horizon. At one hundred feet above sea level, the curve of the earth limits visual distance to around 24, 000 yards on a clear day, while the visual horizon from a point thirty feet above sea level was around 12, 000 yards. This is why turret elevations generally leveled off at between fifteen- and thirty-degrees during World War 1. Most high-powered heavy guns could reach 24, 000 yards at fifteen degrees, while going to twenty or thirty gave insurance against hull damage causing lists. Suddenly at the end of and after the war, navies were demanding a minimum of forty degrees elevation. What changed? The ability of the capital ship to carry and launch aircraft, aircraft that had a flight endurance of two to four hours and transceivers, that were light in weight, reliable and powerful enough to be put into an aircraft light enough to operate from a flying off platform or catapult carried aboard a capital ship. The observer could be put over the target and correct fall of shot to the maximum ballistic range of the gun. By 1935, the US Fleet could successfully engage a target ship at 30, 000 yards over a smoke screen by air spotting. The IJN intended for its Battle Line to open an engagement at more than 35, 000 yards using air spotting. Air spotting did have its limitations. One navy or the other had to establish air supremacy (or at least air superiority, which is why multiple aircraft were carried, to make up for losses) over the battle area. There had to be multiple aircraft to maintain spotters over the battle area. Radio procedures had to be developed to ensure ships were working with the right spotters and engaging the right targets. Aerial spotters had to be trained. Most ship’s captains were reluctant to use seaplanes if they had to recover them, since this involved slowing or even stopping their ship, making it more vulnerable to submarines. Poor visibility or bad weather would limit or prohibit the launching of aircraft. The aircraft and the aviation fuel represented a fire danger to the ship, especially when installed near ventilation systems that provided air to closed spaces like engineering or ready service

[Superimperatoris]

On vacation at the beach, just about the lay down and this drops. Life is good right now. Thanks for making my day Drach!

[oconnorsean]

After finding your channel a year ago I finally got a video that's only an hour old! It's taken me a year to catch up. Drach I absolutely love the work you do and if not for your channel I never would have found the battle ship New Jersey channel. WW 2 engineering and the family history of service to our great country is in my heart. Thank you for sharing your passion and knowledge!!!

[Niels_Larsen]

Sometimes someone forgets not just how old computers are, but how complex calculation they could do.

[EDKguy]

Periscope has a great film breaking down analog computation and fire control computers so that even a math-phobe like me can understand.
Thanks for this Drach!

[MartinCHorowitz]

I did a lot of work on Counter battery RADAR in the 1990's Which would track a shell in flight, and would project back to the launch point so you could shoot back before the original shell landed. It also predicted the landing point, so you could warn people to move out of the way.

[StevenPalmer-csix]

In early 1987 I was on USS Constellation (CV-64) in lieu of my senior training cruise on TSGB (Training Ship Golden Bear). USS New Jersey (BB-62) was docked astern and Connie's Training Officer arranged a tour. In 1990 during RIMPAC '90 I watched USS Missouri (BB-63) conduct a firing. We were 1500 yards off her stern. The sequence was the 5 inch mounts firing 10 rounds rapid continuous fire. Then the 16 inch guns fired forward to after, first by barrel and then by turret. The finale was a full broadside with the 16 inch and 5 inch guns.

[FrankBarnwell-ximy]

About 1/3rd through.
Thank you Drachinifel. Idk how best gets better.
I know it now.

[davidgoodson]

When I was in the RN in the 1960's I worked on the UK equivalent the AFCB MK10 fitted on the Daring class. A true marvel of engineering.

[johnshepherd]

The West Virginia was refitted with the same system and scored a blind fire first salvo hit at 22kyds. I am surprised Dr Scholes did not mention that.

[FrenchieQc]

Listening to these explanations makes you appreciate even more the genius of Admiral Ching Lee!

[schwinglo]

Quite honestly, I think this may be your finest ever video. Utterly fascinating.

[michaelsnyder]

Three of the most important events in US gunnery occurred before 1921. The first was the proof that with careful spotting and calculations, effective fire could be placed on a moving ship (a radio controlled target in 1912) at ranges unthinkable before director controlled were developed. The second was adopting AC electricity. This allowed for more accurate transmission and response to inputs and outputs within a fire control system, such as own ship data and transmission of firing solutions. The third was the capture or acquisition (by any means) after WW1 ended of German synchronizing motors. This eventually, along with AC, allowed for a faster, more accurate fire control computer (Rangekeeper Mk.8), faster and more accurate transmission of data between director, fire control center and turrets, such that US capital ships after 1937 were equipped with switch boards in the fire control centers allowing any turret or secondary mount to be controlled by any fire control director. Fire control could be switched between the forward and aft Mk.38 fire control directors in minutes. In the IJN, the transfer of control between fore and aft main gun directors started with bringing the turrets back to 0 or 90 degrees and a complex actuation of circuit breakers and switches, taking at least 30 minutes. The synchronizing motors also allowed for the use of remote power control of turrets and mounts from the Rangekeeper or Computer in both train and elevation. The RN did not achieve a similar capability until after the war. The IJN never did achieve RPC on heavy and secondary turrets and mounts.
Another module in the fire control system that was almost revolutionary was the stable vertical (artificial horizon maintained by gyros). Only the USN fully implemented the stable vertical which meant that after 1935 could maintain lock on target when the target and the firing ship turned through 90 degrees at no more than 20 knots. No other navy had this capability.
The adoption of 10cm and 3cm surface search and fire control radars (with sufficient power) meant that at any time in most sea states, USN warships could detect, acquire and maintain target lock over the horizon. At 100 feet above sea level, the visual horizon is around 24kyds. The best the Japanese could do was 20kyds with the fire control mod to the Type 22 10cm surface search sets. The Germans never pushed below 40cm and relied, like the other navies on illumination rounds and searchlights. The longest range illumination rounds (IJN) reached 21kyds and searchlights (again IJN), 8800 yds. The British were one step behind the Americans because their electronics industry just couldn't keep up with demand, so that on a few battleships and cruisers got the 10cm Type 274, most making do with the Type 284M at 40cm. As I pointed out in the post on dispersion, the three rebuilt USN battleships engaged a Japanese battleship at 20-25kyds and could have began firing at 30 kyds. And this was with a modified FCS from Cleveland light cruisers integrated with their Mk.1 or Mk.8 rangekeepers, though they also had RPC. The USS New Jersey was straddling a Japanese DD with HC rounds at the end of the Marshall Islands campaign in January 1944 (IIRC) into a setting sun with both ships on more or less parallel courses at over 30 knots at 39kyds, straddles that would have ensured a hit on a Japanese CA, CB or BB. This sort of accuracy only occurred before the war in fire control exercises by the USN and IJN using aerial spotting at 30kds, both battle lines steaming on parallel courses around 20kts. Both sides even practiced laying smoke screens between the battlelines so that only aerial spotting would be effective (this was another push to increased numbers of carriers and fighters, as the spotting aircraft, types like the OS2U or E7K or E13A could only operate under conditions of air supremacy). The modern US fire control systems allowed the USN to think on straddling and hitting on the first or second full salvo, which they did in October 1944. But the USN actually had this capability for capital ships, starting with the South Dakota II class in late 1942 (the North Carolina class had the complete FCS but was using the 40cm Mk.1 (FA) radar, basically equivalent to the Mk.3 (FC), the South Dakotas introducing the 10cm Mk.8)

[diceman]

AT LAST! A video to explain what I've wanted to know for ten years!

[HeedTheLorax]

Something to enjoy with my coffee this morning, so awesome.

[chucks]

Cousin survives Pearl Harbor on USS Maryland as firecontrolman standing atop the cage mast watching for the fall of shot. Went to work for RCA helped develop the Aegis weapons system told me after spending time on Iowa during Korea that those 4 ships were the ultimate weapons system and later said they would be immune to a electromagnet pulse.

[kemarisite]

By the mid-50s, the M-48 tank had a similar "iron idiot" ballistic computer that incorporated mechanical linkages to the "ears" of the coincidence rangefinder on the sides of the turret.

[Ebolson]

I'll finally be seeing New Jersey in a few days and am super excited