NAVAL ORDNANCE AND GUNNERY
VOLUME 2, FIRE CONTROL

CHAPTER 20
MAIN BATTERY SYSTEMS
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Chapter 20 Main battery systems
A. General
B. A typical system
C. Gun directors
D. Fire control stations
E. Main-battery plotting room
F. Turret fire control equipment
G. Main Battery radar
                                                          A. General

20A1. Introduction

Main-battery fire control systems in battleships and cruisers, other than antiaircraft cruisers, are designed primarily to handle the surface fire control problem, discussed in chapter 19. Although the present trend is toward development of automatic major-caliber guns capable of handling either the surface or the air problem, the great majority of main-battery systems now installed have very limited secondary provisions for antiaircraft fire.

The control of turret batteries against aircraft is made possible on most ships by interlocking arrangements between the main battery and the dual-purpose systems. The variety and complexity of these cross-connections preclude their analysis in this text.

20A2. System elements

The principal elements of a main-battery fire control system are located in four types of stations aboard ship. These stations are:

1. The control stations.

2. The aloft gun directors.

3. The plotting rooms.

4. The turrets.

20A3. Central systems

The Gunnery Officer has a station of his own, accessible to the Commanding Officer, and better protected than the gun directors. In battleships and some cruisers, this station is protected by heavy armor and is known as the fire control tower. In many ships there is a similar station aft from which all or part of the main battery may be controlled.

Either or both of these stations may be equipped to take over many of the functions of both the director and the plotting room in case of casualty, or they may serve merely as supervising and observing stations. In either case periscopes and indicating equipment are installed. In addition, there may be some of the following equipment:

1. Auxiliary gun directors, such as the Mark 40 or Mark 55.

2. Auxiliary computers (Mark 3 or Mark 6).

3. Control consoles, as well as indicators, for the Radar Equipment Mark 13.

4. An independent radar equipment (Mark 27).

5. A stable element (Mark 6) for use with the auxiliary computer.

20A4. Aloft gun directors

All battleships and cruisers have two primary gun directors, each equipped with both a radar and a rangefinder. The forward primary director is also the ship’s primary spotting station and is usually under the direct personal command of the ship’s leading spotter.

Cruisers of the Baltimore, Oregon City, Cleveland, Fargo, and Brooklyn classes are equipped with Gun Directors Mark 34 of various Mods. This director mounts a Rangefinder Mark 45. New heavy cruisers of the Salem class have Gun Directors Mark 54, which differ from the Mark 34 in having more complete provisions for control of the main battery against aircraft. The accompanying rangefinder is the Mark 66.

Battleships of the North Carolina, South Dakota, and Iowa classes and large cruisers of the Alaska class mount Gun Directors Mark 38, equipped with Rangefinders Mark 48. This director differs from the Mark 34 principally in that it does not provide a stand-by source of gun orders as does the Mark 34.

Radar Equipment Mark 13 is used with all directors mentioned, although some of the older ships still have the earlier Radar Equipment Mark 8. Some of the subassemblies of the radar are not physically located in the director.

20A5. Plotting rooms

Main-battery plotting rooms, located below the waterline and inside the armor belt, characteristically contain:

1. Rangekeepers, including associated graphic plotters. Various modifications of the Rangekeeper Mark 8, differing from each other chiefly in the ballistic cams, are built for use with the following guns: 16”/50 caliber, l6”/45 caliber, l2”/50 caliber, 8”/55 caliber (both types), and 6”/47 caliber.

2. Stable-vertical gun directors. South Dakota class battleships are equipped with the Mark 43, while all the other ships under discussion use the Mark 41.

3. Some units of the radar equipment.

4. A fire-control switchboard and an associated battle-telephone switchboard.

5. Various indicators.

Cruisers, except for the Salem, and Worcester classes, have one main-battery plotting room, containing only one rangekeeper and stable vertical. In case of casualty or divided fire, auxiliary equipment and procedures must be used. Battleships and the Salem and Worcester class cruisers have duplicate rangekeepers and stable verticals, located in some ships in the same compartment, in others in separate compartments.

20A6. Turrets

As mentioned in chapters 7 and 10, some of the ship’s fire control equipment is located in the turrets. Except for the latest types of turrets, equipped with radars instead of rangefinders, there is little difference between classes of ships in this respect.