FIRE CONTROL DEFINITIONS
|E1. GENERAL DEFINITIONS
GUN-TARGET (GT) LINE is the line joining a ship delivering gunfire support and the target.
OBSERVER-TARGET (OT) LINE is the line joining the naval gunfire shore spotter and the target.
The HORIZONTAL is a plane tangent to the earth’s surface or parallel to such a plane.
A VERTICAL PLANE is a plane perpendicular to the horizontal. It may pass through any designated line or point.
A TRAVERSE PLANE is a plane determined by a point of aim and the elevation axis of the sight.
The REFERENCE PLANE for a battery is an arbitrarily chosen plane, usually within the ship, from which angles of elevation of all battery elements are measured. In practice, it may be the plane containing one of the battery roller paths, or it may be an imaginary plane.
LEVEL ANGLE is the inclination of the battery reference plane with the horizontal, measured in a plane that contains the line of sight. The latter plane may be either the vertical or a plane perpendicular to the reference plane, depending on the design of the control equipment.
CROSSLEVEL ANGLE is the inclination of the battery reference plane with the horizontal, usually measured in a plane perpendicular to the plane in which level is measured. The latter plane may be either the vertical or a plane perpendicular to the reference plane, depending on the design of the control equipment.
TRUNNION TILT is the instantaneous inclination of the axis of the trunnions to the horizontal.
ROLL is the instantaneous value of the angle between the reference plane and the horizontal, measured in an athwartship vertical plane.
PITCH is the instantaneous value of the angle between the reference plane and the horizontal, measured in a fore-and-aft vertical plane.
Note: For purposes of naval gunnery both roll and pitch are measured and recorded as rates; that is, in terms of amplitude per unit time, ordinarily as total degrees of roll (or pitch) per minute.
STABILIZATION is the technique of correcting for deck inclination.
POINT OF AIM is that point on a target at which the sight is directed.
LINE OF SIGHT (LOS) is the straight line joining the sight and the point of aim.
Axis of the Bore is the extension of the axis of the gun bore. It is tangent, at the muzzle, to the trajectory of a projectile fired from the gun.
LINE OF FIRE (LOF) is the straight line joining the gun and the point of impact (or burst) of the projectile. As used in safety precautions for target practices, the line of fire is assumed to include all points near the bearing of the line of fire.
TARGET ANGLE is the relative bearing of own ship from the target, measured in the horizontal from the bow of the target clockwise from 0 degrees to 360 degrees.
POSITION ANGLE is the vertical angle between the horizontal and the line of sight to an elevated target.
RELATIVE TARGET BEARING is the bearing of the target from the firing ship measured in the horizontal plane from the bow of own ship clockwise from 0 degrees to 360 degrees.
TRUE TARGET BEARING is the true bearing of the target from the firing ship.
GENERATED TARGET BEARING (RELATIVE or TRUE) is the relative or true bearing of the target as determined in a computing instrument from previous positions of own ship and target and established rate of change of bearing.
WIND DIRECTION is the direction from which the wind is blowing.
TRUE WIND is the wind as it exists with respect to the earth and independent of any motion of the ship.
APPARENT WIND is the wind apparent at the observing station, and is the resultant of the true wind and the motion of the observing station.
PARALLAX is the angular difference which results from making observations or computations to one target from two different stations. Train, or horizontal, parallax is the angular difference measured in the horizontal plane. Elevation, or vertical, parallax is the angular difference measured in the vertical plane.
BEARING RATE is the rate of change of target bearing from own ship caused by the relative motion of own ship and target. It may be expressed in knots (linear measure) or in degrees per minute (angular measure).
RANGE RATE is the rate of change of range in yards per minute caused by relative motion of own ship and target.
ELEVATION RATE is the rate of change of target elevation (position angle) in degrees per minute. ANGLE OF CLIMB or Dive is the vertical angle between the horizontal and the direction of motion of the target measured in degrees at the target.
RATE OF CLIMB is the rate of change of altitude measured in feet per minute or in knots.
LOADING DEAD TIME is the time between the instant a projectile is removed from the fuze pot and the instant
of firing that projectile. For practical purposes, when firing mechanical-time-fuzed projectiles, the average loading dead time of the battery is the dead time for which correction must be made.
SIGHT ANGLE is the vertical component of the angle between the line of sight and the axis of the bore.
GUN ELEVATION is the vertical angle between the horizontal plane and the axis of the bore.
A MIL is a unit of angular measurement. It is equal to the angle whose tangent is 1/1,000, and is equivalent to 3.44 minutes or 3 minutes 26 seconds of arc. (The Army defines MIL as the angle subtended by an arc equal to 1/6,400th part of the circumference of a circle.)
AZIMUTH is the angle in mils (Army definition) measured from grid north to the OT line.
GUN TRAIN ORDER is the signal transmitted to the guns indicating the angle in the reference plane from own ship’s bow clockwise to the perpendicular plane through the axis of the bore.
GUN ELEVATION ORDER is the signal transmitted to the gun indicating the gun elevation above the deck plane measured in a plane through the bore axis perpendicular to the deck plane.
RANGE is the distance from a station on own ship to the target or some other designated point.
SLANT RANGE is the distance to an aerial point or target.
HORIZONTAL RANGE is the horizontal component of slant range.
ALTITUDE is the vertical component of slant range. (Since this definition disregards the curvature of the earth, it should not be applied beyond the limits of present gun fire control systems.)
PRESENT RANGE is the best available measurement of the range to the target.
ADVANCE RANGE is present range combined with the corrections and predictions necessary to compensate for own-ship and target motion during the time of flight, plus ballistic corrections and spots.
GUN RANGE is the range listed in the range table corresponding to gun elevation.
HITTING GUN RANGE is gun range corrected for the error of MPI.
NAVIGATIONAL RANGE is the best distance to the target, used in post-firing analysis.
BALLISTIC CORRECTIONS are corrections in range and/or deflection to compensate for known or predicted errors, for drift, for wind, and for all variations from standard range-table conditions.
INITIAL BALLISTIC CORRECTION is that part of the ballistic corrections not automatically compensated for by the fire control system.
ARBITRARY BALLISTIC CORRECTION is an empirical correction in range or deflection to compensate for all indeterminate errors in the fire control problem. It is obtained from an analysis of previous firings. This is commonly referred to as ACTH (arbitrary correction to hit).
CONTROL BALLISTIC CORRECTIONS consist of the correction to the gun range and deflection to obtain the sight scale range and deflection.
BALLISTIC WIND is the effective wind, determined by computation, of such force and direction that its action on the projectile during the time of flight will be the same as the combined actions produced by the various true winds acting in the strata through which the projectile will pass as it moves along its trajectory.
BALLISTIC RANGE WIND is the horizontal component of the ballistic wind parallel to the target bearing.
BALLISTIC CROSS WIND is the horizontal component of the ballistic wind at right angles to the target bearing.
BALLISTIC DENSITY is the single air density, determined by computation, which would have the same range effect on the projectile as the actual densities throughout the trajectory.
SUPERELEVATION is the angle the gun must be elevated above the line of sight to compensate for the curvature of the trajectory caused by the force of gravity acting on the projectile.
DEFLECTION is the lateral angular correction (converted to the deck plane where necessary) which is applied to the target bearing in the deck plane to obtain gun train order.
INITIAL VELOCITY is the velocity of the projectile at the instant the projectile leaves the gun.
NOMINAL INITIAL VELOCITY is the initial velocity assigned a new gun with the propellant at a temperature of 90° F.
RANGE-TABLE INITIAL VELOCITY is the initial velocity for which the range table is computed.
A SALVO consists of one shot or several shots fired simultaneously or nearly so by the same battery at the same target.
THE PATTERN of a salvo in range is the distance measured parallel to the line of fire between the shot of the salvo falling or bursting at the greatest distance from the firing point and the shot falling or bursting at the shortest distance, excluding wild shots. In deflection it is the distance measured at right angles to the line of fire between the shot falling or bursting at the greatest distance to the right and the shot falling or bursting at the greatest distance to the left, excluding wild shots.
THE MEAN POINT OF IMPACT (MPI) is the origin of a set of rectangular coordinates so located that the algebraic sums of the distances of the several impacts from the three axes are each equal to zero.
The DISPERSION of a shot is the distance of the point of impact of that shot from the MPI of the salvo. Dispersion in range is measured parallel to the line of fire, and in deflection at right angles to the line of fire in a horizontal plane.
THE APPARENT MEAN DISPERSION of a salvo in range (or deflection) is the arithmetical average of the dispersion in range (or deflection) of the several shots of the salvo, excluding wild shots.
ERROR OF THE MEAN POINT OF IMPACT is the distance of the MPI from the target or other reference point, measured parallel to the line of fire for range and at right angles to the line of fire for deflection.
A STRADDLE is obtained from a salvo in range (or deflection) when, excluding wild shots, a portion of the shots of that salvo fall or detonate short and other shots of the salvo beyond the target (right and left, respectively, for deflection). (In naval gunfire support this may be known as a BRACKETING SALVO.)
A BRACKET is a succession of two salvos, one over and one short, or one right and one left, with no straddles.
A WILD SHOT is a shot with an abnormally large dispersion in range, or, in deflection, or in both.
THE DANGER SPACE for a material target is the distance in front of the target, measured parallel to the line of fire, that the target could be moved toward the firing point, so that a shot striking the base of the target in its original position would strike the top of the target in its new position.
THE Hitting SPACE for a material target is the distance measured parallel to the line of fire between a shot striking the top of the target and one striking the waterline on the engaged side of the target.
E2. CONTROL is authority, less than full command, exercised over the armament or a portion thereof.
A. SUPERVISORY CONTROL is the direction of the over-all employment of the vessel’s armament. It is concerned with the disposition of the batteries to best meet existing conditions, the interior communications plan to be used, the selection and designation of targets for batteries or groups thereof, and the designation of standard procedure to be employed. Supervisory control is exercised by the Gunnery Officer, assisted by his Battery Officers, and by CIC Liaison Officers.
B. BATTERY CONTROL is the direction of the employment of all the mounts or turrets of a similar caliber or purpose in a vessel. It is concerned with the disposition of the mounts or turrets with respect to the fire control stations of the battery, the interior communications plan to be used, the designation and acquisition of targets by the battery or group, and the standard procedures to be employed. The Battery Control Officer is assisted by Group and Sector Control Officers, and by CIC Liaison Officers.
1. BATTERY CONTROL is classified as to TYPE by the manner in which the command of the battery is exercised.
a. COLLECTIVE BATTERY CONTROL is that type of battery control in which the direction of the employment of the battery is centralized. (This type of control may leave a primary director unemployed, and the latter will be considered in STAND-BY CONTROL.)
b. DISPERSED BATTERY CONTROL is that type of battery control in which the direction of the employment is decentralized.
(1) DIVIDED BATTERY CONTROL is that form of dispersed control wherein a battery with two directors is divided into forward and after batteries for command purposes. This form of control is associated with centerline, single-purpose batteries.
(2) Sector Battery CONTROL is that form of dispersed control in which a battery with multiple directors is divided into sectors for control purposes. This form of control is associated with dual-purpose and automatic weapon batteries.
2. BATTERY Control as to METHOD prescribes the grouping of the mounts or turrets with fire control stations, command communications channels between fire control stations, and procedures for designation and acquisition. For a particular vessel the groupings are prescribed in the battle bill.
C. GROUP CONTROL is the control of a specified group of a battery. It is concerned with the type and method of fire control, the procedures to be employed, and the acquisition and destruction of designated targets, as well as the detection of undesignated targets appearing in the assigned sector of fire. Group Control is exercised by the Group Control Officer, assisted by Director Officers, Mount Captains or Turret Officers, and CIC Liaison Officers.
D. SECTOR CONTROL is the control of one group of a battery, or two or more groups of different batteries, each of which is assigned the same sector of fire. It is concerned with the acquisition and destruction of designated targets appearing in the sector. Sector Control is exercised by the Sector Control Officer, assisted by Group Control Officers, and CIC Liaison Officers.
E. The organized system by means of which the offensive power of armament is controlled is known as FIRE CONTROL.
1. FIRE CONTROL is classified as to TYPE by the system employed. For each type of fire control the battle bill of the vessel specifies the instruments to be employed.
a. PRIMARY FIRE CONTROL prescribes the utilization of the principal system. This is the system provided to control before damage occurs to this system.
b. SECONDARY FIRE CONTROL prescribes the utilization of an alternate system to give greater flexibility of control.
c. AUXILIARY FIRE CONTROL prescribes the utilization of a system provided solely to substitute for a primary system in case of damage.
d. LOCAL FIRE CONTROL provides for the control of a single gun mount or a turret from a local station in or adjacent to the mount or turret.
2. FIRE CONTROL is classified as to METHOD by the procedures employed in the direction of the fire of the battery.
a. DIRECT FIRE CONTROL is the control procedure employed when the target is observed from the firing vessel visually or by radar.
b. INDIRECT FIRE CONTROL is the control procedure employed when the target is unobserved by the fire control instruments of the firing vessel.
c. OFFSET FIRE CONTROL is the control procedure employed when a point of aim of known relation-ship to the target is observed from the firing vessel.
E3. TARGET INDICATION is a manifestation, to Command and Control, of targets approaching into or appearing in the area of gunfire. It includes all information available for proper designation, including the presence, identity, location, size, number, course, speed, and estimate of intent, plus any additional evaluated factors which are necessary for proper designation.
A. TARGET INDICATION is classified as to TYPE by the means by which target presence is manifested.
1. RADAR INDICATION prescribes manifestation of target presence by radar.
2. VISUAL INDICATION prescribes manifestation of target presence by visual sighting.
B. TARGET INDICATION is classified as to METHOD by the system employed to display target presence.
1. AUTOMATIC INDICATION is indication of targets by means of an electromechanical system capable of indicating in one display all targets appearing in the area under investigation.
2. MANUAL Indication is the indication of targets by means of a manual plot of all targets observed or reported in the area under investigation.
E4. TARGET DESIGNATION is the selection of the targets which are to be taken under fire, and transmission of the requisite information for acquisition to the selected fire control station or stations.
A. TARGET DESIGNATION is classified as to TYPE by the station originating the designation.
1. COMMAND DESIGNATION is the designation of a target by a command station.
a. OTC designating vessel to take target under fire.
b. CO of vessel designating target to be taken under fire.
2. CONTROL DESIGNATION is the designation of a target from a fire control station.
3. LOCAL DESIGNATION is the designation of a target by mount or turret personnel.
B. TARGET DESIGNATION is classified as to METHOD by the procedure employed for designation.
1. AUTOMATIC DESIGNATION is the designation of the target by means of instruments which transmit sufficient data to the selected gun fire control system to result in target acquisition.
2. PARTIAL AUTOMATIC DESIGNATION is the designation of the target by means of a partially automatic system which must be aided by coaching in order that the selected director will be positioned to acquire the target.
3. VERBAL DESIGNATION is the designation of the target by voice or telephone.
E5. TARGET ACQUISITION is the process of positioning the tracking apparatus of a control system so that a designated target is gated in the radar or fixed in the optics or open sights.
E6. AIMING is the process of establishing target position in bearing and elevation.
A. AIM is classified as to TYPE by the instrument employed:
1. RADAR AIM prescribes determination of target bearing and elevation by radar.
a. PARTIAL RADAR AIM prescribes determination of bearing by radar and determination of elevation by stabilizing equipment.
2. OPTICAL AIM prescribes determination of target bearing and elevation by optical instruments.
a. PARTIAL OPTICAL AIM prescribes determination of target bearing by optical instrument and elevation by means of stabilizing equipment.
3. GENERATED AIM prescribes the generation of target bearing and elevation, and corrections thereto for deck inclination, by means of a computer and stabilizing equipment.
B. AIM is classified as to METHOD by the manner in which the aiming system is operated.
1. CONTINUOUS AIM prescribes continuous measurement of target position in bearing and elevation.
a. CONTINUOUS AUTOMATIC AIM prescribes automatic continuous aiming with the aiming instrument.
b. Continuous AIDED AIM prescribes continuous aiming with the aiming instrument positioned by signals received from the computer and with the resulting position corrected by the operators.
c. CONTINUOUS MANUAL AIM prescribes continuous aiming with the aiming instrument positioned by hand, using either direct manual drive or local power.
2. Intermittent AIM prescribes periodic measurement of target position in one element and continuous measurement in the other.
a. SELECTED ELEVATION prescribes determination of target position continuously in bearing and intermittently in elevation.
b. SELECTED TRAIN prescribes determination of target position continuously in elevation and intermittently in train.
E7. RANGING is the process of establishing target distance from the firing ship.
A. RANGING is classified as to MEANS by the instrument employed:
1. RADAR RANGING prescribes determination of target distance by radar.
2. OPTICAL RANGING prescribes determination of target distance by rangefinder.
3. GENERATED RANGING prescribes the generation of target distance by a computer.
4. ESTIMATE RANGING prescribes the determination of target distance by estimation.
5. NAVIGATIONAL RANGING prescribes the determination of target distance by navigational means.
B. RANGING is classified as to TYPE by the frequency with which the range is established.
1. CONTINUOUS RANGING is that type of ranging in which target distance is continuously established.
2. INTERMITTENT RANGING is that type of ranging in which target distance is established at intervals.
C. RANGING is classified as to METHOD by the procedure employed to operate the instrument.
1. MANUAL RANGING is that method of ranging in which the ranging instrument is operated by hand.
2. AIDED RANGING is that method of ranging in which the generated change of range is introduced into the ranging instrument and upon which corrections are superimposed manually by the rangefinder or radar operators, as required.
3. AUTOMATIC RANGING is that method of ranging in which the ranging instrument automatically determines target distance of an acquired target.
E8. TRACKING is the process of establishing the path of target motion with respect to the firing ship and is accomplished by combining the data obtained by the aiming and ranging processes.
A. TRACKING is classified as to TYPE by the form of tracking employed.
1. DIRECT TRACKING is that type of tracking in which target path is established by direct observation (radar or optical).
2. INDIRECT TRACKING is that type of tracking in which the range, bearing, and elevation of the target are generated by the computer and its associated equipment.
3. Offset TRACKING is that type of tracking in which the target path is established by the direct observation of an intermediate point of aim in known relationship to the designated target.
B. TRACKING is classified as to METHOD by the manner in which the computers are employed to determine the path of target motion.
1. AUTOMATIC TRACKING is that method of tracking in which the target path is established by use of radar for aiming and ranging and without manual operation of any of the tracking controls in the fire control system.
2. AUTOMATIC LEAD COMPUTING is that method of tracking in which the process of aiming automatically generates a solution of target motion. This method of tracking is associated with instruments using gyros to measure the angular velocity of the LOS.
3. RATE CONTROL is that method of tracking in which the computer’s generated path of estimated target motion is made to coincide with the observed path of target motion by comparing the observed and generated rates of motion.
a. AUTOMATIC RATE CONTROL is that method of rate controlling in which the generated target motion is automatically corrected to agree with the observed target motion by a rate-control mechanism operated by the director operators.
b. SEMIAUTOMATIC RATE CONTROL is that method of rate controlling in which the generated target motion is automatically corrected to agree with the observed target motion by a rate control mechanism operated by the computer operators.
c. MANUAL RATE CONTROL is that method of rate controlling in which the generated target motion is corrected to agree with observed target motion by changes to target course, speed, and angle of climb introduced manually by the computer operators.
E9. PREDICTING is the process of determining future target position. Predicting operations are accomplished in computers simultaneously and automatically with tracking.
E10. GUN LAYING is the process of positioning guns in train and elevation in a predetermined relationship with respect to the line of sight. The line of sight may be established at an aloft director or generated in the plotting room, or it may be established at the gun.
A. GUN LAYING is classified as to TYPE by the manner in which guns are positioned:
1. CONTINUOUS GUN Laying. Guns are positioned continuously in accordance with the computed signals and loaded at any position.
2. INTERMITTENT GUN LAYING. Guns are positioned when loaded, but must be returned to a specified position after firing for loading.
B. GUN LAYING is classified as to METHOD by the means by which guns are positioned.
1. AUTOMATIC GUN LAYING. Guns are positioned automatically by remote control systems in accordance with signals received.
2. INDICATOR GUN LAYING. Guns are positioned locally in accordance with signals received. Positioning may be effected by either local power or manual drive.
3. LOCAL GUN LAYING. Guns are positioned locally by gun-sight telescope. Positioning may be effected by either local power or manual drive.
E11. GUN FIRING is the process of shooting a gun or guns.
A. GUN FIRING is classified as to MEANS by the firing system employed.
1. ELECTRIC Firing provides for the shooting of a gun by an electrical system controlled by either:
a. LOCAL KEY provides for firing by means of a key actuated at the gun mount or turret.
b. Master KEY provides for firing by means of a key actuated at a station remote from the mounts or turrets, such as a director or control station.
(1) AUTOMATIC KEY is a form of master key firing in which an automatic contact maker is employed to fire at a selected firing point.
2. PERCUSSION Firing provides for the shooting of guns by mechanical firing mechanism at the gun mount or turret.
B. GUN FIRING is classified as to TYPE by the rate at which guns are shot.
1. RAPID FIRE is that type of fire in which no check fire is used for purposes of applying corrections.
2. SLOW FIRE is that type of fire in which the fire is deliberately delayed to allow for the application of corrections or to conserve ammunition.
3. DELIBERATE Fire is that type of slow fire which is executed on a prearranged time schedule.
C. GUN FIRING is classified as to METHOD by the manner in which individual guns are shot with respect to the other guns of the battery.
1. SALVO FIRE is the simultaneous firing of all guns ready and aimed at the same target.
2. FULL SALVO FIRE IS the simultaneous firing of all guns of a group.
3. SPLIT SALVO FIRE is the firing of less than the full number of guns in a multiple gun mount or mounts at a given instant.
4. PARTIAL SALVO FIRE is the firing of less than the full number of mounts or turrets (in multiple gun-mount batteries) at a given instant.
5. CONTINUOUS FIRE is the firing of each gun without regard for the readiness of other guns of the battery.
E12. SPOTTING is the estimation of the required correction of range, elevation, deflection, and fuze range to hit the target. The SPOTTER is the person actually observing the fall of shot or burst and making the estimates of required corrections. A SPOT is the correction estimated by the spotter.
A. Spotting is classified as to MEANS by the station from which the observation is made:
1. SHIP SPOT indicates that the spotter is stationed in the firing ship at a designated spotting station.
2. LOCAL SPOT indicates that the spotter is stationed in the firing ship at or adjacent to a mount or turret.
3. SHORE SPOT indicates that the spotter is stationed ashore.
4. Air SPOT indicates that the spotter is stationed in an aircraft or airship.
B. Spotting is classified as to TYPE by the manner in which observations are made:
a. Eye Spotting is the term used to indicate observations made by eye without the use of optical instruments.
b. OPTICAL Spotting is the term used to indicate that observation is assisted by optical aids, including ordinary binoculars, spotting binoculars fitted with mil scales, spotting glasses, or stereoscopic range finders.
a. RADAR SPOTTING is the term used to indicate that the observation is made by radar.
C. SPOTTING is classified as to METHOD by the manner of estimating the error of burst or impact.
1. DIRECT SPOTTING is that method in which the spotter’s correction is based on his estimate of the error of the mean point of impact from the target. A direct spot may be made on the fall of shot of one salvo or as the result of an observation of an initial ladder.
2. BRACKET AND HALVING is a method used in visual spotting at extremely long ranges, from low spotting stations, or with poor illumination, when the spotter can determine whether the shots are short or over, but the amount of error cannot be estimated with reasonable accuracy. On observing the initial fall of shot, a spot is made which is believed to be sufficiently large to ensure crossing the target. if the next salvo crosses the target, the following spot is applied in the opposite direction (towards the target) but is half the amount of the initial spot. Successive spots are in the same direction until the target is crossed again. When this occurs, the direction of the spots is again reversed and again halved. The process is continued until the target is located within the pattern.
E13. LADDERS are a succession of salvos fired with known and predetermined changes between successive salvos, to ensure early establishment of hitting gun range and deflection in surface fire, to serve as a yardstick for covering an area target, or to increase pattern size.
A. LADDERS are classified as to TYPE by the element in which laddering takes place.
1. DEFLECTION LADDERS are ladders fired with predetermined changes in deflection on successive salvos. They are seldom used in our Navy, except for covering area targets or in radar spotting when the discrimination of fire control radar makes a deflection rocking ladder advisable.
2. RANGE LADDERS are ladders fired with predetermined changes in range on successive salvos.
3. ELEVATION LADDERS are ladders fired with predetermined changes in elevation between successive salvos. They are seldom used in our Navy.
B. LADDERS are classified as to METHOD by the manner in which the predetermined arbitrary corrections are introduced.
1. INITIAL LADDERS are ladders in which, in addition to known increments or steps, the number of salvos is definitely known. This number is greater than two, and the steps are sufficiently large, so that the target will be located within the limits of the ladder.
2. ADD LADDERS are fired with the initial gun range less than the best range and with successive steps of the ladder fired with increasing ranges, each increasing range spot not less than the pattern size.
3. DROP LADDERS are fired with the initial gun range greater than the best range and with successive steps of the ladder fired with decreasing ranges, each decreasing range spot not less than the pattern size.
4. CONTINUOUS LADDERS are fired with a continuous application of spots, applied in such a manner as to move the salvos back and forth across the target.
a. SPOTTER-CONTROLLED LADDER is a form of continuous ladder in which the spotter or observer determines all or part of initial direction, when to change direction, size of first ladder steps, and when the ladder is reversed. For simplicity, the size of steps of the first ladder and successive ladders is usually prearranged. The initial correction of the first ladder may be directed by doctrine or other orders.
b. ROCKING LADDER is a form of continuous ladder in which the number of Steps of the ladder before reversal of direction and the size of the steps are both specified beforehand. The object is to increase the pattern size and still maintain sufficient projectile density to ensure hits. The steps of the ladder are never larger than the pattern size, and the number of steps is such as will ensure covering probable ranging and aiming errors and target maneuvers during time of flight. If used with continuous fire the steps are applied at regular predetermined time intervals; if with salvo fire, after each salvo.
E14. BARRAGES are a barrier of fire executed on predetermined firing data. The initial shots are placed across the probable path of the target.
A. BARRAGES are classified as to METHOD by the manner in which position of the bursts is varied.
1. LINE-OF-SIGHT BARRAGE is a barrage using fixed fuze setting and varying sight settings, with each shot so directed that bursts will occur in the instantaneous line of sight to the target.
2. FIXED-ZONE BARRAGE is a barrage fired with fixed sight settings. Once the target has passed through the zone of fire, a second zone may be selected and a new barrage fired.
3. CREEPING-ZONE BARRAGE Is a barrage in which the fuze settings are varied in such a way as to advance along the track at a rate slower than that of the actual target advance.