Fire Control Fundamentals, NAVPERS 91900, 1953, was created to introduce sailors to the basics of weapons fire control. The basic fire control principles of gun against a surface target are then applied to the control of Antiaircraft guns, Antisubmarine Weapons, Torpedoes, Rockets and Guided Missiles.

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Image of the the cover.
Fire Control Fundamentals, 1953, Rating Specialization Training Series, Bureau of Naval Personnel, NAVPERS 91900

Copyrighted by Van Valkenburgh, Nooger and Neville, Inc., 15 Maiden Lane, New York 38, N. Y
Unrestricted, royalty-free use has been granted to the Department of the Navy. 1953


Trainee Knowledge Level:

The knowledge level required for proper understanding of "Fire Control Fundamentals" and its application to Navy equipment is that of a trainee who has mastered the following subjects:

"Basic Electricity"
"Basic Electronics"
"FT Rating Indoctrination"

Drawing of sailor studying.







The story of fire control





The purpose of this series of instruction sheets is to introduce you to some of the many things you will encounter in your work as a Fire Control Technician. You will get an overall view of the history of fire control and a brief summary of its present-day applications. You will see how the basic fire control principles, developed for firing a gun at a surface target are applied to the control of antiaircraft guns, antisubmarine weapons, torpedoes, rockets and guided missiles.

The basic fire control principles of.. GUN against Surface Target.. are applied to the control of
Antiaircraft guns, Antisubmarine Weapons, Torpedoes, Rockets and Guided Missiles.

You will learn what the major; components of various modern fire control systems are and what function each serves. As you learn more about fire control, you will realize that the Navy is only as strong as its fire power, and in order for that fire power to be effective, it must be accurately controlled. That's where you-as a Fire Control Technician-play a vital part in making your ship an effective weapon against enemy ships, planes and submarines. It will be your job to operate and maintain the many complex devices used in your ship's various fire control systems.




Your Job as a Fire Control Technician

After you learn the theory of fire control, you will not automatically become a proficient fire control technician. Your duties as a fire control technician will be many and varied. You will be called upon to operate and maintain many different kinds of mechanical and electrical devices. You must be a mechanic and know how to use hand tools, gages and instruments effectively to adjust and repair mechanical fire control devices. You must also be an electrician, for you'll be working with electronic circuits, electric motors, and switchboards. Your battle station may be at a gun director tracking the target, in the plotting room operating various computing devices, or operating a radar set to determine target range and accuracy of fire. Whatever or wherever your station, you must know how to operate and maintain your equipment.

The fire control technician must maintain and operate fire control equipment.

You have been selected to study fire control because the Navy believes you have the many varied qualities necessary to become a fire control technician. Now let's go on and learn more about the challenging and vital problem of controlling the Navy's fire power-fire control!




The Story of Gunpowder and Early Guns

Gunpowder, first developed by the Chinese many centuries ago, was not used for anything but entertainment (fireworks) for a long time after its discovery. The discovery of the principle of the gun-that is, using an explosion to fire a projectile from a tube-was made accidentally in the thirteenth century by a man who was trying to turn mercury into gold. According to the story he added an ingredient which caused his mixture to explode, blowing the top off his kettle. Repeating the experiment several times gave him the idea for a weapon which became known as a "gun." From such a humble beginning developed the intricate and powerful weapons of today which certainly aren't for "entertainment."

This discovery-Made THIS possible.  Drawing showing explosion in kitchen and battleship gun.

Early guns were very crude and unpredictable, often more dangerous to the gunner than the enemy. For many years arrows and spears were more effective than guns in combat. A crossbow bolt could penetrate a knight's armor; the early guns couldn't. The archer could fire several arrows while the gunner was loading and firing a single round.

Drawing of archer smiling while bullets bounce off of his armor.

Many improvements in firearms were required before guns became a useful weapon. Stone projectiles were replaced by those made of bronze and then lead and iron balls in the fourteenth century, and as time went on gunpowder and guns were also improved to the point where gunnery became an important art.




The Story of Gunpowder and Early Guns (continued)

Guns were used on ships on a large scale for the first time in the fifteenth century, when a Spanish fleet opened fire with cannon at point-blank range on the Turkish fleet, which was quickly defeated. Subsequent sea and land battles involving firearms began to prove the effectiveness of guns if properly used in combination with other weapons. By the middle of the sixteenth century guns of many sizes and kinds were being used, some of them 10 feet long, capable of firing a 4-1/2 inch iron shot 500 feet per second for a distance of 2000 yards. These were soon exceeded by a Mohammedan cannon which fired a 400-pound projectile more than two miles. Gunnery was beginning to come into its own!

Less than 200 years ago, naval guns were fired at point-blank range; gunnery was still an art, not a science, and fire control was largely a matter of skillful seamanship in maneuvering the ship into position to enable the gunners to hit the target. The range and destructive power of guns continued to increase over the years, from an average effective range of 100 yards in the mid-1800's to more than 40,000 yards today. Methods of fire control in the modern sense were not developed until the nineteenth and twentieth centuries. You will trace the development of gun sighting systems and fire control devices on the next few sheets.

Range and Firepower have steadily increased.  In 1800s-100 yards, Today-40,000 yards+




The Development of Gun Sighting Systems

The first concern of a fire control system is to provide an effective way of aiming. This is the function of the gun sights. Prior to 1800, there was no need for elaborate gun sighting systems, because the guns themselves were inaccurate except at close range. Guns were simply pointed at the target by eye.

Gun sights introduced early in the nineteenth century consisted of fixed front and rear sights mounted so that the line of sight across their tips was parallel to the bore of the gun. Toward the end of the nineteenth century, a sight telescope was developed by a Navy Lieutenant. It consisted of a simple telescope containing a pair of crosshairs, and was mounted in such a way that the line of sight could be moved with respect to the axis of the gun to correct for some of the factors which affect the solution of the fire control problem. Present-day gun sights take many forms, but they still perform the basic function of all gun sights-to provide a horizontal and vertical offset between the line of sight and the axis of the gun bore in order that the target may be kept in sight while the gun is aimed so that the fired projectile will hit the target.

Before 1800s, Guns were pointed in general direction of target.  Early 1800s, Front and rear fixed sights.  Late 1800s, Early telescope sights.  Present 16 in. gun sight. Gun Sighting methods improved over the years are basically the same.




Early Fire Control Developments

Improvements in gun sighting systems alone, however, were not enough, as the range and intricacy of guns increased. It became necessary to develop other fire control instruments which could accurately and rapidly solve the fire control problem. The first of such devices was the stadimeter, an optical device used to measure range, which enabled the gunner to determine range more accurately than could be done by eye. The stadimeter was crude and good only for short ranges, but embodied a principle later used in the rangefinder.

Crude Stadimeters led to the development of...
Rangefinders and increased accuracy of Range Determination.

The largest and most important corrections in fire control are to compensate for the relative motion between gun and target. In the old days the positions of gun and the target at the moment of impact of projectile were predicted by eye. In the early 1900's an improvement was brought about by marking the position of the target on paper as it moved along its course (by measuring distance and direction from ship to target) from which it was possible to determine the approximate course and future position of the target. This let to the development of the rangekeeper, a device which automatically corrects for changes in target range. The range-keeper was refined and improved till it reached its present form, making possible the rapid solution of other factors in the fire control problem.

Graphical plotting led to Mechanical Rangekeepers.




Early Fire Control Developments (continued)

Another factor which had to be taken into consideration to obtain accurate fire was the inclination of the gun caused by the roll and pitch of the ship's deck. One early device used by nautical gunners was a round shot suspended from a spar. The gunner watched this improvised pendulum and fired his piece just before it was parallel to the mast (when the deck was horizontal). This same principle was later incorporated in the "stable element" and the "stable vertical." These devices act like a child's spinning top, in that their axes always remain truly vertical, thus establishing a reference plane from which gun elevation angles can be measured.

A hanging ball, this simple device used the same principle as the stable vertical.

A final factor which had to be considered to provide an effective fire control system was accurate determination of where each shot fell. In the early days each gun crew worked out its own sight settings and the gun was fired as soon as that gun crew had corrected the aim of their particular piece. With all guns firing independently it was impossible to spot the individual gun's effectiveness with any accuracy. The central control station, from which all guns were controlled, was developed to correct this inaccuracy. A new instrument called a "director" was installed in the control station. At first the director was a pair of "master" gun sights, from which settings were transmitted to the guns. As time went on, the gun director became more complicated and performed more jobs, which you will learn about a little later

Pointer Fire gave way to Centralized Control




The Major Components of a Modern Fire Control System

On the three previous sheets you learned about the early development of gun sighting systems and fire control devices, and why it was necessary to develop certain pieces of equipment to perform specific tasks. The illustration on this sheet shows a typical modern fire control system and its major components. It is not necessary at this time for you to learn the details of how and why all of the components function. Your job now is simply to become generally familiar with what the major components are, their primary function and how they are related.

A typical fire control system.  Gun director, rangekeeper, stable vertical, ship's gyro, pitometer log.




The Function of Fire Control System Components

The principal components of a fire control system, as shown on the preceding sheet, are the gun director, the rangekeeper (or computer), the stable vertical (or stable element) and the gun turrets, as well as related auxiliary equipment (ship's gyro, pitometer log, communication systems, etc).

The gun director is located high in the ship's superstructure to provide as distant a horizon as possible. By means of optical equipment and/or radar (an electronic device which you will study later, used to locate objects by means of reflected radio waves), the director is able to track the target and measure its range, bearing (direction from ship to target), course and speed. It transmits this information to the rangekeeper and stable vertical, which are located in the plotting room below decks. The rangekeeper takes the information from the director, combines it with information on own ship's course (from the ship's gyroscope) and speed (supplied by the pitometer log), and continuously computes the predicted target position. It then transmits orders to the gun turrets, which are equipped with automatic equipment to train and elevate the guns in accordance with the orders received from the rangekeeper. The stable vertical measures the inclination of the deck and supplies this information to the director and rangekeeper which incorporate the necessary corrections in their computations.

Location of fire control systems components.  Director, Plotting room.

The complexity and arrangement of the components of fire control systems will vary widely depending upon the ship, its armament, whether the system controls main, secondary or antiaircraft batteries, how many guns are controlled, and other factors. Basically, however, the major elements always serve the same function-the director sights and tracks the target, the rangekeeper (computer) calculates the required gun settings and the turrets aim the guns. Remember this and you'll be well on your way to understanding fire control.




A Survey of Modern Surface Fire Control Systems

A surface fire control system, as the name implies, is designed to control the fire of guns used against surface targets-that is, enemy ships or shore installations. Of course, the surface fire control system of a battleship is much more complex than that of a destroyer. Now let's take a look at some typical surface fire control systems as found on various types of ships.

A battleship is equipped with two main battery directors and two plotting rooms-one of each located forward and one aft. Either director together with the equipment in either plotting room can be used to control all or part of the main battery. In addition, equipment in each main battery turret permits emergency individual control of the guns.

Secondary batteries on a battleship consist of 5-inch dual purpose guns used against aircraft as well as surface targets. There are four secondary battery directors, any one of which can be used to control one or all of these guns. They can also be used, if necessary, to control the main battery. The two secondary battery plotting rooms are similar to the main battery plotting rooms, in that each contains two rangekeepers (computers), two stable elements and the necessary auxiliary equipment.

Main and secondary Armament and Gun Directors on a Battleship.




A Survey of Modern Surface Fire Control Systems (continued)

Cruisers have fire control installations similar to those of battleships, except that there are only two directors for the dual purpose secondary battery.

Main and secondary armament and gun directory on a cruiser.

On a destroyer, the main battery is also the dual purpose battery, and consists of a number of 5-inch guns. There is only one main battery director and one plotting room, which control all guns. As on the larger ships, provision is made for individual control of each turret in the event that the director is damaged or destroyed by enemy action.

Main armament and gun director on a destroyer

Because of the greater complexity and flexibility of the armament on a battleship, it is apparent that a more complex fire control system is required.

Naval ships are armed with weapons other than those designed for use against surface targets. On the following sheets you will learn something about the fire control systems used to control antiaircraft, and antisubmarine weapons, torpedoes and guided missiles.




Antiaircraft Fire Control Systems

Antiaircraft fire control systems of various types are designed to control guns ranging in size from light machine guns through 6-inch dual purpose.

Battleships and heavy cruisers are equipped with secondary batteries consisting of dual purpose guns, which are used against aircraft as well as surface targets. The main battery on a destroyer consists of a number of 5-inch dual purpose guns. The fire control systems used with these weapons for surface fire also control them when they are used against enemy aircraft. These guns are used for long range fire at high or distant air targets, and are centrally controlled as explained on the two preceding sheets.

The other antiaircraft guns carried by Navy ships are 3-inch, 40-mm and 20-mm automatic guns. The number and arrangement of these guns depends on the type of ship carrying them. The 3-inch and 40-mm guns-called the "heavy machine-gun battery"-are equipped with a separate director and fire control system. Decentralized control permits firing at many targets at once; however, in an emergency cross connections permit the heavy machine-gun directors to control the dual purpose guns and vice versa.

Cruiser antiaircraft armament and gun directors

The light machine guns (20-mm) are equipped with individual lead-computing sights.




Antiaircraft Fire Control Systems (continued)

There are two general classes of antiaircraft fire control systems: (1) "linear-rate systems" which determine changes in target position, course and speed by measuring the distance between successive target positions; and (2) "relative-rate systems" which measure the angular velocity of the line of sight to determine target motion. The theory of operation of these two systems will be explained later.

The linear-rate system is used as the primary means for control of 5-inch dual purpose guns for both surface and antiaircraft fire. The relative-rate system of fire control was developed during World War II when increased speeds made it necessary to reduce the time required for solution of the problem of hitting aircraft, since this time is limited by the relatively short range of machine guns. Although originally used only for light machine guns (20-mm), systems of this type have been designed to control 40-mm, 3-inch and 5-inch guns.

Linear-rate systems control dual purpose guns (aircraft and surface ship).  Relative-rate systems control automatic guns (antiaircraft)




The Antisubmarine Attack Problem

The primary weapons used by surface vessels against submarines are torpedoes, depth charges and ahead-thrown missiles. Depth charges are either rolled off the stern of the attacking ship or projected a small distance to the side, while ahead-thrown missiles are projected to a position (controllable within narrow limits) ahead of the attacking ship. Torpedoes may be fired to the side, ahead or behind the attacking ship (within certain limits), and continue on a set course under their own power. The fire control problem is thus largely a tactical one, since it is necessary to solve the problem of maneuvering the ship into attack position.

Methods of anti-submarine attack.  Depth charge release tracks, starboard depth charge projectors, ahead-thrown missile projector, torpedo tubes.

When depth charges are used, the attack position is ahead of the submarine to allow for the sinking time of the charges. For ahead-thrown missiles and torpedoes it is not necessary for the ship to pass ahead of the submarine, since the missiles are aimed to fall at the indicated target position. In either case, however, it is necessary to determine (1) the course along which the attacking ship must be steered, and (2) the time to fire, so that the depth charges or missiles will arrive at the predicted target position at the same time as the submarine.




A Survey of Antisubmarine Fire Control Systems

Before an attack can be made on an enemy target-whether it is on the surface, in the air or underwater-the attacking ship must locate the target and determine its bearing, range, course and speed. For surface and air targets this information is obtained by means of the gun director and rangefinder as previously discussed. Underwater targets cannot be detected with this equipment, however, since they are not visible and radar is useless underwater. Submerged vessels are detected by "sonar" which uses reflected sound waves instead of radio waves as in radar to detect and determine underwater target range and bearings.

SONAR uses reflected sound waves to locate underwater targets.

A sound wave generator, called a sonar transducer, is located below the waterline of the attacking ship. It transmits sound waves which reflect back to the ship after hitting an underwater object. By measuring the time required for the sound waves to reach the target and return, it is possible to determine the range; bearing is the direction from which the waves were reflected. Target course and speed can be calculated by observing changes in range and bearing.

Once the above factors are known, it is necessary to determine own ship's course and the proper time for firing, as opposed to gun elevation and train orders required for surface or antiaircraft fire control.




A Survey of Antisubmarine Fire Control Systems (continued)

The antisubmarine fire control system on board the general purpose destroyer (the most common non-specialized submarine fighter) normally consists of the following units: (1) the sonar equipment, which transmits and receives the sound waves to locate the target; (2) the sonar range recorder, which automatically records the range received from the sonar equipment, and passes this information on to (3) the attack director, which also receives target bearing information from the sonar, ship's bearing from the gyro and ship's speed from the pitometer log. The attack director's job is to solve the fire control problem-that is, determine ship's attack course and time to fire.

The attack plotter displays on a screen a picture of the movement of own ship and target, and may be used to solve the fire control problem graphically in case of failure of the attack director.

Sonar transducer, attack plotter, sonar range recorder, attack director, ship's gyro, pitometer log

You will learn more about these components and their operation a little later.




A Survey of Torpedo Fire Control Systems

The torpedo is recognized as the most effective underwater weapon of naval warfare; it may be of the "homing" or "non-homing" type. Our discussion here will pertain only to the non-homing type. Torpedoes may be fired from submarines, aircraft or surface vessels, for each of which the torpedo fire control problem is quite different. When firing torpedoes from aircraft, submarines or PT boats, it is necessary to have the ship pointed at least in the general direction of the target. A destroyer, however, is equipped with torpedo tubes which can be trained to aim at the target.

Two kinds of control are used for destroyer torpedo fire: (1) "bridge control, " the primary method of control on modern destroyers, which is remote control from directors; and (2) "local control, " in which the proper settings are made at each mount by means of the torpedo tube mount sight, when the director control system is inoperative. The primary function of the torpedo director is to control the tube mounts by electrically indicating to them the proper settings to obtain the desired torpedo course for scoring a hit.

Bridge method of torpedo fire control.  Torpedo tube director, torpedo tube mount sight (for local control), torpedo tube mount.

Destroyers usually fire their torpedoes in a "spread," to increase the chances of scoring a hit on an enemy who is probably aware that he is being attacked and is therefore taking evasive action. You will learn more about the use and control of torpedoes later on.




A Survey of Rocket and Guided Missile Fire Control Methods

Short range barrage rockets have proved to be effective weapons in shore bombardments. The principal ship used to fire rockets is the LSMR, which mounts ten rocket launcher assemblies. Any one or all of these launchers may be controlled by either of two duplicate rocket fire control systems. Each system includes a gun director, a stable element, a gun order corrector and auxiliary components, all of which were developed for the control of conventional guns, but have been successfully converted to the control of rocket launchers.

Rocket armament of an LSMR

The conventional projectile fired from a gun, or the barrage rocket, is committed to a given course at the time of firing. The target may change course or speed during the time of the projectile's flight, in which case the result is a miss. A guided missile, however, is subject to control so that it will alter course after launching in order to score a hit regardless of the target's evasive tactics! In order to control such a missile it is necessary to know the relative positions of missile and target at all times, and to be able to effect appropriate alterations to the missile's course from a remote position. To accomplish this, guided missile fire control systems include components carried by the missile which receive and carry out directions received from radar and computing equipment on the ground.

Guided missile fire control




How You Are Going to Learn the Fundamentals of Fire Control

On the preceding sheets you read about the history of guns and fire control devices, you learned about the main components of a fire control system, and you took a quick look at some of its specialized applications in antiaircraft, antisubmarine, torpedo, and rocket and guided missile fire control systems. In continuing your study of fire control fundamentals you will learn about the theory of guns and ballistics-what happens to a projectile while in the gun and during flight. Then you will go deeper into the basic fire control problem-that of hitting a moving target from a moving ship. You will learn more about the various components of a fire control system, how they perform their jobs, and their application in surface, antiaircraft, antisubmarine, torpedo, rocket and guided missile fire control systems. Finally, you will be given an introduction to some of the Navy's special equipment used in fire control devices, including radar, sonar, synchros and servos.

You will learn about these things by studying these information instruction sheets and discussing what you read with your instructor and your classmates. You will be given plenty of opportunity to ask questions and make comments about what you read. If something is not clear to you, ask about it, because there is much to be learned, and it is important that you fully understand each lesson before proceeding to the next.

You will learn fire control fundamentals by studying and discussing the information instruction sheets.  Reading, Discussing.

Now that you know what and how you are going to study, let's get started by reading about guns and interior ballistics.

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