Military

CHAPTER 5

ADJUSTMENT OF FIRE

This chapter implements STANAG 2934, Chapter 6 and QSTAG 505.

Section I

SUBSEQUENT CORRECTIONS

5-1. PURPOSE OF ADJUSTMENT

An observer's prime concern is the placement of timely and accurate fires on targets. If an observer can locate the target accurately, he will request FIRE FOR EFFECT in his call for fire. Failure to locate the target accurately may result from poor visibility, deceptive terrain, poor maps, or the observer's difficulty in pinpointing the target. If the observer cannot locate the target accurately enough to warrant FFE, he may conduct an adjustment. Even with an accurate target location, if current firing data corrections are not available, the FDO may direct that an adjustment be conducted. Normally, one gun is used in adjustment. Special situations in which more than one gun is used are so noted throughout this discussion.

NOTE: Some helpful notes for the observer are at the end of this chapter, HELPFUL NOTES FOR THE OBSERVER.

5-2. ADJUSTING POINT

When it is necessary for the observer to adjust fire, he must select an adjusting point. In area missions, he must select a well-defined point near the center of the target area on which to adjust the fire. The point selected is called an adjusting point (Figure 5-1). The location of this point is included in the target location element of the call for fire in an area fire mission. In the conduct of a registration or destruction mission (precision fire), the adjusting point is the target itself.

5-3. SPOTTINGS

A spotting is the observer's determination of the location of the burst (or the mean point of impact [MPI] of a group of bursts) with respect to the adjusting point as observed along the OT line. Spottings are made for the following:

  • Deviation (the number of mils right or left of the OT line).

  • Distance (whether the burst occurred beyond or short of the target).

  • When fuze time is fired, the HOB (the number of mils the burst is above the target).

Figure 5-1. ADJUSTING POINT IN AN AREA FIRE MISSION

Spottings must be made by the observer the instant the bursts occur except when the spottings are delayed deliberately to take advantage of drifting smoke or dust. The observer is usually required to announce his spottings during his early training; experienced observers make spottings mentally. The observer should consider the most difficult spottings first. The sequence of spottings is HOB (air or graze), range (over or short), and deviation (left or right).

a. Height-of-Burst Spotting. The HOB spotting may be any one of the following:

  • AIR--a round or group of rounds that bursts in the air. The number of mils also is given. For example, a burst 10 mils above the ground would be spotted as AIR 10.

  • GRAZE--a round or group of rounds that detonates on impact.

  • MIXED--a group of rounds that results in an equal number of airbrushes and graze bursts.

  • MIXED AIR--a group of rounds that results in both airbrushes and graze bursts when most of the bursts are airbrushes.

  • MIXED GRAZE--a group of rounds that results in both airbrushes and graze bursts when most of the bursts are graze bursts.

b. Range Spotting. Definite range spottiness are required to make a proper range adjustment. Any range spotting other than DOUBTFUL, LOST, or UNOBSERVED is definite. Normally, a round which impacts on or near the OT line results in a definite range spotting. Figure 5-2 shows the approximate areas for various range spottiness. An observer may make a definite range spotting when the burst is not on or near the OT line by using his knowledge of the terrain, drifting smoke, shadows, and wind. However, even experienced observers must use caution and good judgment when making such spottiness. Possible range spottiness are as follows:

  • OVER--a round that impacts beyond the adjusting point.

  • SHORT--a round that impacts between the observer and the adjusting point.

  • TARGET--a round that impacts on the target. This spotting is used only in precision fire (registration or destruction missions).

  • RANGE CORRECT--a round that impacts at the correct range.

  • DOUBTFUL--a round that can be observed but cannot be spotted as OVER, SHORT, TARGET, or RANGE CORRECT.

  • LOST--a round whose location cannot be determined by sight or sound.

  • UNOBSERVED--a round not observed but known to have impacted (usually heard).

  • UNOBSERVED OVER or SHORT--a round not observed but known to have impacted over or short.

NOTE: For safety considerations regarding lost and unobserved rounds, refer to AR 385-63.

Figure 5-2. RANGE SPOTTINGS

c. Deviation Spotting.

    (1) A deviation spotting is the angular measurement from the adjusting point to the burst as seen from the observer's position. During a fire mission, the observer measures the deviation, in mils, with his binoculars (or another angle-measuring instrument). Deviation spottings are measured to the nearest 5 mils for area fires and 1 mil for precision fires. Possible deviation spottings are as follows:

  • LINE--a round that impacts on line (LN) with the adjusting point as seen by the observer (on the OT line).

  • LEFT--a round that impacts left (L) of the adjusting point in relation to the OT line.

  • RIGHT--a round that impacts right (R) of the point in relation to the OT line.

EXAMPLE

An observer spots a round to the right of the OT line. He measures the angular deviation as 40 mils. His deviation spotting is 40 RIGHT.

    (2) Deviation spottings are taken from the center of a single burst or, in the case of platoon or battery fire, from the center of the group of bursts. Deviation spottings should be made as accurately as possible to help in obtaining definite range spottings.

EXAMPLES

If the adjusting point is at the center of the binocular reticle pattern, the observer would spot the round in Figure 5-3 for deviation as 30 LEFT.

The observer would spot the round in Figure 5-4 for deviation as LINE.

d. Unobserved Spotting. At times, the observer may be able to make a spotting even though he is unable to see the round impact.

EXAMPLE

The observer hears but does not see the round impact and the only possible place the round could have impacted and not been visible to the observer is in a ravine beyond the adjusting point. He assumes that the burst is beyond the adjusting point and spots it as UNOBSERVED, OVER.

Figure 5-3. DEVIATION SPOTTING 30 LEFT

Figure 5-4. DEVIATION SPOTTING LINE

e. Lost Spotting. If the observer is unable to locate the round (either visually or by sound), the round is spotted LOST.

    (1) A round may be lost for various reasons:

  • It may be a dud (nonfunctioning fuze), resulting in no visual or audible identification.

  • The terrain may prevent the observer from spotting the round or its smoke.

  • The weather may prevent the observer from spotting the round or its smoke.

  • Enemy fire may prevent the observer from hearing or seeing the round.

  • The FO simply may have failed to spot the round.

  • Errors by the FDC or the firing piece may cause the round to be lost.

    (2) When dealing with a lost round, the FO must consider his own experience, the level of FDC and/or gun section training, and the location of friendly elements with respect to the target. The observer should take corrective action based on his confidence in the target location, the accuracy of fire on previous missions, whether the lost round is an initial round or a subsequent round, and the urgency of the mission.

    (3) When a round is lost, positive action must be taken. The observer can start a number of corrective procedures, such as one or more of the following:

  • Begin a data check throughout the system, starting with his target location data and his call for fire.

  • Request a WP round, a smoke round, or a 200-meter airburst with HE on the next round.

  • Repeat.

  • End the mission and start a new mission.

  • Make a bold shift. The observer should be very careful in making a bold distance or deviation change when the target plots in the vicinity of friendly troops.

5-4. TYPES OF CORRECTIONS

After a spotting has been made, the observer must send corrections to the FDC to move the burst onto the adjusting point. The corrections are sent, in meters, in reverse of the order used in making spottings; that is, deviation, range, and HOB.

a. Deviation Corrections.

    (1) The distance in meters that the burst is to be moved (right or left) is determined by multiplying the observer's deviation spotting in mils by the OT distance in thousands of meters (the OT factor). Deviation corrections are expressed to the nearest 10 meters. A deviation correction less than 30 meters is a minor deviation correction. It should not be sent to the FDC except as refinement data or in conduct of a destruction mission.

    (2) To determine the OT factor when the OT range is greater than 1,000 meters, the range from the observer to the target (OT distance) is expressed to the nearest thousand and then expressed in thousands.

EXAMPLE

OT range = 4,200 meters
OT distance (expressed to nearest thousand) = 4,000
OT factor (expressed in thousands) = 4

    For an OT range less than 1,000 meters, the distance is expressed to the nearest 100 meters and expressed in thousands.

EXAMPLE

OT range = 800 meters
OT factor = 0.8

    (3) The computed deviation correction is announced to the FDC as LEFT (or RIGHT) (so much). The correction is opposite the spotting.

    (4) Determination of deviation corrections is shown in Table 5-1.

NOTE: Table 5-1 expresses 1,500 and 2,500 meters to the nearest even OT factor. For an explanation of artillery expressions see TC 6-40. For example, express to the nearest even number when halfway between two numbers.

Table 5-1. DETERMINATION OF DEVIATION CORRECTIONS

    (5) Angle T (Figure 5-5) is the angle formed by the intersection of the gun-target (GT) line and the OT line with its vertex at the target. If angle T is 500 mils or greater, the FDC should tell the observer this. If the observer is told that angle T is 500 mils or greater, at first he continues to use his OT factor to make his deviation corrections. If he sees that he is getting more of a correction than he asked for, he should consider cutting his corrections to better adjust rounds onto the target.

Figure 5-5. ANGLE T

b. Range Correction. When making a range correction, the observer attempts to "add" or "drop" the adjusting round, along the OT line, from the previous burst to the target. If his spotting was SHORT, he will add; if his spotting was OVER, he will drop. The observer must be aggressive in the adjustment phase of an adjust fire mission. He must use every opportunity to shorten that phase. He should make every effort to correct the initial round onto the target and enter FFE as soon as possible. Successive bracketing procedures should be used only when time is not critical. When conducting an adjustment onto a target, the observer may choose to establish a range bracket. Different types of range adjustments are discussed in Section II.

c. Height-of-Burst Corrections. See Figure 5-6.

    (1) One gun is used in adjusting fuze time. The observer adjusts HOB (after a 100-meter range bracket has been established by using fuze quick) to obtain a 20-meter HOB in fire for effect. He does this by announcing a correction of UP or DOWN (so many meters).

    (2) If the spotting of the initial round is GRAZE, an automatic correction of UP 40 is sent. If the round is an airburst, the HOB of the round (in meters) is computed (HOB spotting in mils above the adjusting point multiplied by the OT factor). The appropriate HOB correction is given (to the nearest 5 meters) to obtain the desired 20-meter HOB.

    (3) Fire for effect is entered only when a correct HOB is reasonably assured. Therefore, fire for effect is never begun when either the last round observed was spotted as a graze burst or the HOB correction is greater than 40 meters. If the initial rounds in fire for effect are spotted as MIXED, the subsequent surveillance report normally includes the correction UP 20.

Figure 5-6. HEIGHT-OF-BURST SPOTTINGS

5-5. SEQUENCE OF SUBSEQUENT CORRECTIONS

After the initial round(s) impact(s), the observer transmits subsequent corrections until the mission is complete. If the FDC is using BCS or BUCS, all subsequent corrections or transmissions must include the target number or a means of identifying the mission to which the correction applies. These corrections include appropriate changes in elements previously transmitted and the necessary corrections for deviation, range, and HOB. Elements that may require correcting and the order in which corrections are announced are as follows:

  • Observer-target direction.

  • Danger close.

  • Trajectory.

  • Method of fire.

  • Distribution.

  • Projectile.

  • Fuze.

  • Volume.

  • Deviation correction.

  • Range correction.

  • Height-of-burst correction.

  • Target description.

  • Mission type and/or method of control.

  • Splash.

  • Repeat.

Any element for which a change or correction is not desired is omitted. Guidelines for subsequent corrections are discussed below.

a. Observer-Target Direction. In the sequence of corrections, the OT direction is the first item sent to the FDC. It is sent if it has not been sent previously or if the OT direction changes by more than 100 mils from the previously announced direction. (Direction is normally sent to the nearest 10 mils but it can be sent to the nearest 1 mil, depending on the accuracy of the observer's equipment.)

EXAMPLE

An observer began an adjustment on several self-propelled (SP) guns. He used a tree at direction 5620 as the adjusting point During the adjustment, the guns moved to a new position an appreciable distance from the initial adjusting point The observer selects a new adjusting point and measures a direction of 5840 to the new point. Since the difference between the directions to the old and new adjusting points exceeds 100 mils, the first element in the observer's next correction is DIRECTION 5840.

b. Danger Close. If the adjustment of fires brings impacting rounds within danger close distance during the conduct of the mission, the observer must announce DANGER CLOSE to the FDC. The observer, using creeping fire (paragraph 5-6d), makes corrections from the round impacting closest to friendly troops. If the adjustment of fire moves the round outside the danger close distance, the observer transmits CANCEL DANGER CLOSE. Danger close distances are as follows:

  • Artillery or mortars--600 meters.

  • Naval gun 5-inch or smaller--750 meters.

  • Naval gun larger than 5-inch--1,000 meters.

  • 16-inch naval gun (ICM or controlled variable time [CVT])--2,000 meters.

c. Trajectory. The observer requests a change in the type of trajectory if it becomes apparent that high-angle fire is necessary during a low-angle adjustment or that high-angle fire is no longer necessary during a high-angle adjustment. For example, if during the conduct of the mission a target moves into a defilade position, the observer may change trajectory by transmitting the correction HIGH ANGLE. Conversely, if a target moves out of defilade into open terrain and high-angle fire is no longer necessary, the observer requests CANCEL HIGH ANGLE.

d. Method of Fire. The observer transmits any correction he wants to make in the method of fire. For example, if the observer wants to change from one gun to a platoon firing in order from left to right, he transmits the correction PLATOON LEFT. If he wants to change to a platoon firing in order from right to left, he transmits the correction PLATOON RIGHT.

e. Distribution. (See Figures 5-7 and 5-8.) If an observer wants to change the distribution of fire from a BCS sheaf (circular with a 100-meter radius) to another type of sheaf, he transmits the sheaf desired (for example, CONVERGE, OPEN, or LINEAR or the target length, width, and attitude). Conversely, if the observer wants to change from a specific sheaf to a BCS sheaf, he transmits the Correction CANCEL, followed by the type of sheaf being used (for example, CANCEL CONVERGE [or OPEN] SHEAF).

f. Projectile. If the observer wants to change the type of projectile, he announces the desired change (for example, SMOKE or WP).

g. Fuze. If the observer wants to change the type of fuze or fuze action, he announces the desired change (for example, TIME, DELAY, or VT).

h. Volume. If the observer wants to change the volume of fire, he announces the desired change (for example, 2 ROUNDS or 3 ROUNDS). Volume refers to the number of rounds in the fire-for-effect phase.

i. Deviation Correction. If the round impacts to the right or left of the OT line, the observer determines the correction required, to the nearest 10 meters, to bring the round onto the OT line. To make the correction, the observer transmits RIGHT (or LEFT)(so many meters). (Deviation corrections less than 30 meters are not sent to the FDC except when conducting a destruction mission or as refinement data.)

j. Range Correction. If the round impacts beyond the target on the OT line, the observer's correction is DROP (so many meters). If the round impacts between the observer and the target, the range correction is ADD (so many meters).

k. Height-of-Burst Correction. The observer transmits HOB corrections to the nearest 5 meters with the correction UP (or DOWN). In firing fuze time in an area mission, HOB corrections are made after the deviation and range have been corrected to within 50 meters of the target by using fuze quick in adjustment.

l. Target Description. Target description is sent before a control correction during immediate suppression missions and when a new target is being attacked without sending a new call for fire.

m. Mission Type and/or Method of Control. If the observer wants to change the mission type and/or method of control, he transmits the desired method of control (for example, ADJUST FIRE, FIRE FOR EFFECT, or AT MY COMMAND). If the method of control being used includes AT MY COMMAND, his correction is CANCEL AT MY COMMAND.

Figure 5-7. CONVERGED SHEAF

Figure 5-8. OPEN SHEAF

n. Splash. An observer in a tactical situation may have difficulty identifying or observing his rounds. This may be because he has to stay down in a concealed position much of the time or because of other fire missions being conducted in the area. In any case, he may request assistance from the FDC by requesting SPLASH. The FDC informs the observer that his round is about to impact by announcing SPLASH 5 seconds before the round impacts. The observer may end splash by announcing CANCEL SPLASH.

o. Repeat. REPEAT is used (in the adjustment phase) if the observer wants a subsequent round or group of rounds fired with no corrections to deviation, range, or HOB (for example, TIME, REPEAT). REPEAT is also used by the observer to indicate that he wants fire for effect repeated with or without changes or corrections to any of the elements (for example, ADD 50, REPEAT).

Section II

AREA FIRE (ADJUSTMENT AND FIRE FOR EFFECT)

5-6. ADJUSTMENT TECHNIQUES

There are four techniques that can be used to conduct area adjustment fires. Successive bracketing is best when observers are inexperienced or when precise adjustment is required, such as precision registrations and destruction missions. It mathematically ensures that FFE rounds will be within 50 meters of the target. Hasty bracketing is best when responsive fires are required and the observer is experienced in the adjustment of fire. One-round adjustment provides the most responsive fires but generally requires either an experienced observer or an observer equipped with a laser range finder. Creeping fire is used in danger close missions. Upon completion of each mission, refinement data and surveillance are required. From this surveillance the FDC can determine the effectiveness of the fires.

a. Successive Bracketing. After the first definite range spotting is determined, the observer should send a range correction to the FDC to establish a range bracket of known distance (one round over and one round short). Once the bracket has been established, the observer successively splits the bracket until he is assured the rounds will be within 50 meters of the adjusting point when he fires for effect. Normally, range changes of 100, 200, 400, or 800 meters are used to make splitting the bracket easier. The observer enters FFE when he is sure of rounds impacting within 50 meters of the adjusting point.

EXAMPLE

The first round impacts over the adjusting point (see Figure 5-9). The observer should send a drop correction enough to place the next round short of the adjusting point.

Figure 5-9. ROUND IMPACTING OVER THE ADJUSTING POINT

EXAMPLE (CONTINUED)

The observer sent DROP 400 (-400) after observing his first round. The next round impacted short of the adjusting point (Figure 5-10).

The observer has now established a range bracket. He has had one round over and one short of the adjusting point, separated by 400 meters. Using the successive bracketing technique, the observer sends ADD 200 (+200).

The third round impacts over the adjusting point (Figure 5-11). The observer has a 200-meter bracket because round 2 impacted short of the adjusting point and the distance between the two rounds was 200 meters. Splitting the bracket, the observer sends DROP 100 (-100). The fourth round impacts short (Figure 5-12). The observer has established a 100-meter bracket. He now sends ADD 50, FIRE FOR EFFECT. The center of impact of the FFE rounds is now mathematically certain of being within 50 meters of the adjusting point.

Figure 5-10. ROUND IMPACTING SHORT OF THE ADJUSTING POINT

Figure 5-11. ROUND IMPACTING OVER THE ADJUSTING POINT

Figure 5-12. ROUND IMPACTING SHORT OF THE ADJUSTING POINT

b. Hasty Bracketing. Experience has shown that effectiveness on the target decreases as the number of rounds used in adjustment increases. An alternative to successive bracketing is the hasty bracketing technique. Successive bracketing mathematically ensures the observer that the FFE rounds will impact within 50 meters of the adjusting point, however, it is a slow and unresponsive technique. Therefore, if the nature of the target dictates that effective fires are required in less time than the successive bracketing technique would take, the hasty bracketing technique should be used. The success of hasty bracketing adjustment depends on a thorough terrain analysis that gives the observer an accurate initial target location. The observer gets a bracket on his first correction much as in the successive bracketing technique. He uses this initial bracket as a yardstick. to determine his subsequent correction. He then sends the FDC the correction to move the rounds to the target and FIRE FOR EFFECT.

EXAMPLE

The first round impacts approximately 35 mils right and 100 meters short of the adjusting point (Figure 5-13). The observer spots it as SHORT, 35 RIGHT. With an OT factor of 4, the observer sends LEFT 140, ADD 200.

The next round impacts approximately 10 mils left and 50 meters over the adjusting point (Figure 5-14). The observer spots it as OVER, 10 LEFT. He looks at the round and the adjusting point and decides that he needs to go right 40 meters (10 x OT factor of 4) and drop 50. He will then be on his adjusting point. Therefore, he sends RIGHT 40, DROP 50, FIRE FOR EFFECT.

Figure 5-13. SHORT, 35 RIGHT

Figure 5-14. OVER, 10 LEFT

The hasty bracketing technique improves with observer experience and judgment. Each observer must strive to improve his abilities in order to increase responsiveness on the battlefield.

c. One-Round Adjustment. Unlike the preceding two adjustment techniques, this method does not require the establishment of a bracket. The observer spots the location of the first round, calculates and transmits to the FDC the corrections necessary to move the burst of the round to the adjusting point, and fires for effect. This technique requires either an experienced observer or one with accurate distance-measuring equipment such as a laser range finder. All missions conducted by using a G/VLLD should be FFE or one-round adjustments.

d. Creeping Fire (Danger Close). The creeping method of adjustment is used during danger close missions. The observer should make range changes by creeping the rounds to the target, using corrections of 100 meters or less, rather than making large range corrections.

5-7. FIRE FOR EFFECT

The purpose of area fire is to cover the target area with dense fire so that the greatest possible effects on the target can be achieved. The type and amount of ammunition requested by the observer depend on the type of target, its posture, and its activity. Fire for effect is entered during an adjust fire mission when a satisfactory adjustment has been obtained; that is, when the deviation, range, and HOB (if firing fuze time) have been corrected to provide effects on target.

a. Normally, the observer using successive bracketing requests FFE when he splits a 100-meter bracket. Under certain conditions when the PEr of the weapon is 38 meters or larger, an observer is justified in calling for FFE when a 200-meter bracket is split. (In this situation, the FDC notifies the observer that the PEr is greater than 38 meters).

b. If time fuze is used, the observer requests FUZE TIME after range and deviation have been corrected but before announcing FIRE FOR EFFECT. With fuze time, fire for effect is not requested until the HOB is correct or until the observer can compute the correction that should result in the correct HOB. Rules for adjusting fuze time are as discussed below.

    (1) In splitting the 100-meter bracket, the correction is TIME, ADD (or DROP) 50, OVER. If range and HOB are correct (20 meters above ground), the observer sends FIRE FOR EFFECT, OVER.

    (2) After FUZE TIME is requested, no more range or deviation corrections are sent to the FDC.

    (3) If a round with fuze time is spotted as a graze burst and there have been no previous airbursts, the correction is UP 40, OVER.

    (4) If a round with fuze time is spotted as a graze burst and the observer has spotted a previous airburst, the correction is UP 20, FIRE FOR EFFECT, OVER.

    (5) If the observer spots an airburst, he should send the correction to achieve a 20-meter HOB and fire for effect. For example, if the HOB of the last round is 40 meters, the correction is DOWN 20, FIRE FOR EFFECT, OVER.

    (6) Do not fire for effect--

  • From a graze burst.

  • If the correction is greater than DOWN 40.

5-8. REFINEMENT AND SURVEILLANCE

The observer should observe the results of the fire for effect and then take whatever action is necessary to complete the mission. Table 5-2 shows the observer's actions and example transmissions after the FFE rounds have been observed.

Table 5-2. REFINEMENT AND SURVEILLANCE

Section III

PRECISION FIRE

5-9. TYPES OF PRECISION MISSIONS

Precision fire procedures place a great deal of responsibility on the observer. The two types of precision missions are precision registration and destruction. In precision fire, the adjusting point must be accurately located. An eight-digit grid should be sent for precision missions unless the observer is equipped with a laser range finder, which ensures accurate target location.

NOTE: Precision missions, by their nature require a high ammunition expenditure and make the firing unit vulnerable to enemy target acquisition.

5-10. PRECISION REGISTRATION MISSION

A registration is conducted with a single piece. Normally, the FDO directs the observer to conduct the registration on a designated point; however, the observer may be directed to select the registration point. The registration point should be accurately located (within 10 meters), near the center of the zone of fire, semipermanent, located on fairly level terrain if possible, and on common survey with the firing unit.

a. Initiation. The precision registration is initiated with a message to observer as shown in the examples on this page.

b. Impact Registration. The objective of a registration is to get spottings of four rounds (two over and two shorts) along the OT line from rounds fired with the same data or from rounds fired with data 25 meters apart (50 meters apart when PEr is greater than or equal to 25 meters). Normally, this requires the spottiness from four separate rounds. However, a target hit or a round spotted as range correct provides spottings of both over and short. Thus, the objective could be achieved with two consecutive target hits or range correct spottings. Applicable rules and procedures are discussed below.

    (1) The observer spots the rounds for deviation to the nearest 1 mil and brings the rounds onto the OT line before splitting a 200-meter bracket. As a rule of thumb, no deviation corrections should be made after a 200-meter bracket has been established. Once the observer brings the rounds onto the OT line, he measures and records deviation but makes no correction. If a doubtful range spotting is obtained, the observer corrects for deviation only. If a deviation correction is made after a 200-meter bracket is established, the last round fired and all previous rounds cannot be considered as usable rounds for determining range and deviation refinement data.

    (2) When the 50-meter range bracket has been established, two rounds are fired with data 25 meters in the direction opposite that of the last range spotting. If both rounds result in spottings of short (or over), an add (or a drop) of 25 meters with a change in volume to one round is sent. Then firing is continued until another definite range spotting is obtained at the opposite end of the 25-meter range bracket.



EXAMPLES

REGISTRATION ON A KNOWN POINT

FDC to FO:                           H18 THIS IS H44, REGISTER ON
                                     KNOWN POINT 2, QUICK AND
                                     TIME(1), OVER. (Read back by FO)

FO to FDC: DIRECTION 6400, OVER.(2) (Read back by FDC)

FDC to FO: SHOT, OVER. (Read back by FO)

REGISTRATION POINT SELECTED BY THE OBSERVER

FDC to FO: H18 THIS IS H44, SELECT REGISTRATION POINT VICINITY GRID NK6138, QUICK AND TIME, OVER. (Read back by FO)

FO to FDC: GRID NK61243843(3), DIRECTION 6310, OVER.(2) (Read back by FDC)

FDC to FO: SHOT, OVER. (Read back by FO)


1 The announcement of quick and time alerts the observer that impact and time portions will be conducted.
2 The FO's response to the message to observer indicates that he is ready to observe.
3 The FO sends eight-digit grid coordinates for the registration.

    (3) When the requirement of two over and two shorts with the same data or data fired 25 meters apart has been met, the impact registration is ended with necessary refinement data. Refinement data may include either a deviation correction or a range correction, or both, to the nearest 10 meters.

    (4) In determining refinement data for range, the location of the registration point is determined with respect to the two sets of spottings. Then refinement data are determined and announced. The criteria for determining range refinement data are discussed below.

      (a) If the registration point is nearer the last round(s) fired, no range refinement is necessary to move the impact toward the registration point (Figure 5-15).

      (b) If the registration point is equidistant between the two sets of rounds, the observer determines the range refinement to be ADD 10 or DROP 10 from the last data fired (Figure 5-16).

      (c) If the registration point is nearer the pair of rounds at the opposite end of the bracket, the observer determines the range refinement to be ADD 20 or DROP 20 (Figure 5-17).

Figure 5-15. NO RANGE REFINEMENT NECESSARY

Figure 5-16. DROP 10

Figure 5-17. DROP 20

      (d) The observer must keep track of the rounds and how they are spotted in relation to the registration point. This is most easily done by drawing a picture and numbering the rounds on DA Form 5429-R (Figure 5-18).

    (5) Deviation refinement is determined by adding the deviation spottings of the rounds (rds) establishing the two over and two shorts (this may include two, three, or four deviation spottings). This total is then divided by the number of rounds (two, three, or four) to get an average deviation, which is then expressed to the nearest mil. The average deviation multiplied by the OT factor equals the correction, which is expressed to the nearest 10 meters.

    (6) After the impact phase of a registration, the observer transmits refinement data to the FDC (for example, LEFT 10, DROP 20). Normally he commands RECORD AS REGISTRATION POINT. However, since BCS or BUCS uses only known points, the observer may be required to transmit RECORD AS KNOWN POINT. In either case, the FDC must send an MTO assigning a known point number to the registration point.

Figure 5-18. EXAMPLE REGISTRATION DIAGRAM



EXAMPLES

OBSERVER DIRECTED TO CONDUCT AN IMPACT
REGISTRATION

NOTE: Refinement data for impact portion were determined by using rounds 4, 5, 6, and 7.

              Round                         Spotting
                1                             +6R
                2                             -8R
                3                             -5R
                4                             +7R

Sum of deviations is 6R + 8R + 5R + 7R = 26R.
Average deviation is 26R / 4 rounds = 6.5R, approximately 6R.
OT factor is 3.
MPI is 3 x 6R = 18 meters R, approximately 20 meters R.
Correction is LEFT 20, DROP 10, RECORD AS
REGISTRATION POINT, END OF MISSION, OVER.

NOTE: Deviation spottings are expressed to the nearest whole number, and deviation refinement corrections are expressed to the nearest 10 meters.

IMPACT REGISTRATION

              Round                         Spotting
                1                            Target
                2                              +7R
                3                              -3L

Sum of deviations is 0 + 7R + 3L = 4R
Average deviation is 4R / 3 rounds = 1.33R, approximately 1R.
OT factor is 2.
MPI is 2 x 1R = 2 meters R, approxiamtely 0 (no devition correction).
Correction is ADD 10, RECORD AS REGISTRATION POINT.



c. Mortar Registration. Precision registration procedures for mortars are identical to the impact registration procedures for artillery. The exception is that once a 100-meter range bracket has been split and the last fired round is within 50 meters of the target, refinement corrections are sent to the FDC and the mission is ended. Range corrections are made to the nearest 25 meters. Also, only one round over and one round short are required. An example of the last two transmissions to the FDC appear in Figure 5-19.

d. Adjusting the Sheaf for Mortars. One additional step that is not done for artillery but may be required for mortars is adjusting the sheaf. This may be done anytime during a fire mission but may be directed by the FDC after a registration. If so, the FDC will send PREPARE TO ADJUST THE SHEAF, OVER. The purpose of adjusting the sheaf is to get all mortars firing parallel. The mortars will be positioned with tubes numbered 1 through 4 for an 81-mm platoon from right to left as seen from behind the tubes. For a 107-mm mortar platoon, the tubes will be numbered 1 through 6 when employed as a platoon or 1 through 3 when employed by sections. A 60-mm mortar platoon has two tubes.

Figure 5-19. MORTAR REGISTRATION

    (1) To start adjustment of the sheaf, the observer requests SECTION RIGHT (or LEFT) REPEAT, OVER. The entire section will then fire, in order, starting at the right (or left), with 10-second intervals between rounds. The mortar that was used to register will not fire. If the observer requests SECTION RIGHT, REPEAT, OVER for a 107-mm section, Numbers 1 and 3 will fire (in that order). (Number 2 conducted the registration.)

    (2) To adjust the sheaf, all rounds must be adjusted on line at approximately the same range (within 50 meters) and with 40 meters lateral spread between rounds. In adjusting the sheaf, range corrections for rounds impacting within 50 meters of the sheaf are ignored. The sheaf is adjusted perpendicular to the gun-target line. (If angle T is greater than 500 mils, each piece is adjusted onto the registration point and the FDC computes data for the sheaf.) Lateral refinement corrections are made to the nearest 10 meters, but corrections less than 50 meters are not fired. Once refinement corrections for all mortars have been determined, the sheaf is adjusted. An adjusted sheaf for an 81-mm section is shown in Figure 5-20.

Figure 5-20. ADJUSTED MORTAR SHEAF

EXAMPLE

The sheaf of an 81-mm section is being adjusted. Number 2 conducted the registration. The observer has requested SECTION RIGHT, REPEAT, OVER. The rounds fired impact as shown in Figure 5-21.

All rounds are within 50 meters of the correct range. Only Number 3 is more than 50 meters out in lateral adjustment, so the adjustment for Number 3 is sent first. Then the refinement data for Numbers 1 and 4 are sent as follows: NUMBER 3, RIGHT 60, REPEAT; NUMBER 1, RIGHT 30, NUMBER 1 IS ADJUSTED; NUMBER 4, LEFT 20, NUMBER 4 IS ADJUSTED, OVER.

Number 3 is now fired, and the round impacts 10 meters right of the desired burst location as indicated in Figure 5-22. The observer then sends NUMBER 3, LEFT 10, NUMBER 3 IS ADJUSTED, SHEAF IS ADJUSTED, END OF MISSION, OVER.

e. Time Registration. If a time registration is required after the impact registration has been completed, the observer determines and announces refinement data and commands the time registration to be fired; for example, RIGHT 10, ADD 10, RECORD AS REGISTRATION POINT, TIME, REPEAT, OVER.

NOTE: Mortars do not conduct time registration.

    (1) The objective of the time portion of the precision registration is to correct the mean HOB of four rounds fired with the same data to 20 meters above the registration point. If the first round is a graze burst, a correction of UP 40 is given. Once a measurable airburst has been obtained, the command is 3 ROUNDS REPEAT. When four rounds have been fired with the same data, the registration is ended with the appropriate correction to achieve a 20-meter HOB.

    (2) When four airbursts are spotted, the HOB is corrected to 20 meters. The mean HOB is determined by adding the four spottings (in mils), dividing by 4, expressing the sum to the nearest mil, and then multiplying by the OT factor. (This is the same technique used in determining deviation corrections.) The sum is then expressed to the nearest 5 meters, and the appropriate correction is determined to achieve the desired 20-meter HOB. For example, UP 10, RECORD AS TIME REGISTRATION POINT, END OF MISSION, OVER.

    (3) When three airbursts and one graze burst are spotted, the HOB is correct; and no correction is required.

    (4) With two airbursts and two graze bursts, the HOB correction sent is UP 10.

    (5) With one airburst and three graze bursts, the HOB correction sent is UP 20.

    (6) Check rounds may be fired to verify the validity of the time registration; however, they are not necessary. If the first airburst is extremely high, the observer may make a down correction and fire one round. If that round is at a measurable HOB, he can then fire the additional three rounds.

Figure 5-21. SECTION RIGHT, REPEAT

Figure 5-22. NUMBER 3 IS ADJUSTED



EXAMPLE

QUICK AND TIME REGISTRATION (FIGURE 5-23)

Refinement data for the impact portion were determined by
using rounds 5, 6, 7, and 8.
Sum of deviation spottings is 6R + 0 + 4R + 2R = 12R.
Average deviation is 12R / 4 = 3R.
OT factor is 3.
MPI is 3 x 3R = 9 meters R, approximately 10 meters R.
The registration point is nearer the pair of rounds at the opposite end of the bracket from the last round fired.
Correction is LEFT 10, DROP 20, RECORD AS REGISTRATION POINT, TIME REPEAT, OVER.

Refinement data for the time portion were determined by using rounds 9, 10, 11, and 12.
Sum of HOB spottiness is as follows:
AIR 5 + AIR 6 + AIR 3 + AIR 5 = AIR 19.
Average HOB is AIR 19 / 4 = AIR 4.75, approximately AIR 5.
OT factor is 3.
Mean HOB is 3 x AIR 5 = AIR 15 meters.
Correction is UP 5, RECORD AS TIME REGISTRATION POINT, END OF MISSION, OVER.

Summary of airbursts and fuze corrections for four rounds is as follows:
All graze = UP 40.
Three graze and one air = UP 20.
Two graze and two air = UP 10.

One graze and three air = no correction.
No graze and all air = must measure to ensure 20-meter HOB.


Figure 5-23. QUICK AND TIME REGISTRATION



EXAMPLE

QUICK AND TIME REGISTRATION---RANGE CORRECT (RC) SPOTTING (FIGURE 5-24)

Refinement data for the impact portion were determined by
using rounds 4, 5, and 6.
Sum of deviation spottings is 1R + 3L + 2L = 4L
Average deviation is 4L / 3 = 1.33L, approximately 1L
OT factor is 3.
MPI is 3 x 1L = 3 meters L, approximately 0 meters.
The registration point is nearer the last round fired.
Correction is RECORD AS REGISTRATION POINT, TIME REPEAT, OVER.
Refinement data for the time portion were determined by using rounds 7, 8, 9, and 10.
The time portion spottings were 3 AIR and 1 GRAZE (G).
Correction is RECORD AS TIME REGISTRATION POINT, END OF MISSION, OVER.


Figure 5-24. QUICK AND TIME REGISTRATION-RANGE CORRECT SPOTTING



EXAMPLE

QUICK AND TIME REGISTRATION DURING ADJUSTMENT (FIGURE 5-25)

Refinement data for the impact portion were determined by
using rounds 4, 6, 7, and 8.
Sum of deviation spottings is 4R + 1L + 5R + 1R = 9R.
Average deviation is 9R / 4 = 2.25R, approximately 2R.
OT factor is 4.
MPI is 4 x 2R = 8 meters R, approximately 10 meters R.
The registration point is equidistant between the two pairs of rounds.
Correction is LEFT 10, ADD 10, RECORD AS REGISTRATION POINT, TIME, REPEAT, OVER.

Refinement data for the time portion were determined by using rounds 9, 10, 11, and 12.
Spottings were 2 AIR and 2 GRAZE.
Correction is UP 10, RECORD AS TIME REGISTRATION POINT, END OF MISSION.



Figure 5-25. QUICK AND TIME REGISTRATION DURING ADJUSTMENT

f. Second-Lot Registrations. Second-lot registrations are conducted in much the same manner as are first-lot (single) registrations. After the first-lot impact registration has been completed, a time registration is conducted, if required. The FDC must announce to the observer OBSERVE SECOND-LOT REGISTRATION. The observer must reestablish the appropriate range bracket and complete the second-lot registration by using the same procedures as for the first lot. The time portion of the registration is not fired with the second lot.



EXAMPLE

MESSAGE TO OBSERVER FOR A TWO-LOT REGISTRATION

                FCD to FO:   H18 THIS IS H44, REGISTER ON
                             KNOWN POINT 2, QUICK AND TIME,
                             2 LOTS, OVER. (Read back by FO)

AT COMPLETION OF FIRST-LOT REGISTRATION

 
                FO to FDC:   RECORD AS TIME REGISTRATION 
                             POINT, OVER. (Read back by FDC)

FDC to FO: OBSERVE SECOND-LOT REGISTRATION, OVER.



g. Abbreviated Precision Registration.

    (1) At times, the tactical situation or ammunition constraints may prohibit conduct of a full-scale precision registration. Although not as accurate, an abbreviated (abbr) precision registration (Figure 5-26) can provide adequate corrections for the effects of nonstandard conditions. The decision to conduct an abbreviated registration rests with the FDO. For this type of registration, the observer merely shortens the standard procedures.

      (a) Normal adjust fire procedures are followed until a 100-meter bracket is split.

      (b) The correction then sent is ADD (or DROP) 50 METERS.

      (c) The burst which is a result of this correction is spotted, and minor corrections for both deviation and range are sent to the FDC in the following format:

  • For both impact and time portion registrations: LEFT 10, DROP 40, RECORD AS REGISTRATION POINT, TIME, REPEAT, OVER.

  • For an impact only registration: RIGHT 30, DROP 10, RECORD AS REGISTRATION POINT, END OF MISSION, OVER.

      (d) Normal adjust fire, time adjustment procedures are followed in the time portion:

  • An airburst is obtained and then corrected to a 20-meter HOB.

  • Instead of firing additional rounds, refinement is sent to the FDC in the following format: UP 10, RECORD AS TIME REGISTRATION POINT, END OF MISSION, OVER.

    (2) Abbreviated registrations are much more accurate and therefore more feasible if the observer is equipped with a G/VLLD.

5-11. DESTRUCTION MISSION

a. In a destruction mission, one weapon is fired to destroy a point target. It is similar to a registration in that the observer continues adjustments to establish a 25-meter bracket. Once it is established, the observer splits the 25-meter bracket by adding or dropping 10 meters and continues to fire additional rounds. After every third round, an additional refinement is made, and firing is continued until the target is destroyed or the mission is ended. (The observer may make corrections after each round.) For example, the FO makes his refinement as shown in Figure 5-27. The OT factor is 2.

b. Because of the amount of time and ammunition required, destruction missions should be avoided. Only a target that is critical to support a maneuver operation should be engaged in this manner and only if the target cannot be engaged with Copperhead.

Figure 5-26. ABBREVIATED PRECISION REGISTRATION

Figure 5-27. DESTRUCTION MISSION

Section IV

MOVING TARGETS

5-12. ENGAGEMENT

Targets, both planned and opportunity, will often move on the battlefield or begin to move after being engaged during adjustment or FFE. Realistically, targets will not remain stationary for long periods of time. Therefore, observers must be proficient at engaging moving targets. For engagement of targets of opportunity, see paragraph 5-13. For engagement of planned targets, see paragraph 5-14. For engagement of moving targets with Copperhead, see Chapter 6, Section V.

5-13. TARGET OF OPPORTUNITY

A target of opportunity is a target that appears during combat and against which no attack has been prearranged. These targets are expected to be more frequent in highly mobile situations. Requesting fire against a stationary target is a simple matter. The observer determines the target location and sends the call for fire. Requesting fire against a moving target is more complex. The observer must call for fire by using a grid in front of and on the intended path of the vehicle or vehicles and timed so that the rounds and the vehicle(s) arrive at the desired location at the same time.

a. Intercept Point. The point or grid at which the observer wants to engage the moving target is called the intercept point. To predict the intercept point, the observer takes the actions discussed below.

    (1) He determines the moving target direction and speed of travel. After acquiring the target, the observer tracks it until he is sure of the direction in which it is moving. As the target moves from point A to point B (Figure 5-28), the observer can use one of three methods to determine its speed.

      (a) First, he can estimate the speed as follows:

  • Slow--3 meters per second (7 miles per hour [mph]).

  • Medium--5 meters per second (11 mph).

  • Fast--8 meters per second (18 mph).

      (b) Second, he can use the G/VLLD to measure the distance the target moves during a certain time interval. As the target moves, the operator lases it and converts the polar data to grid locations, points A and B. Then he determines how far the target moved by measuring the distance between points A and B and rounding to the nearest 1 meter. He divides the distance traveled by the time interval between points A and B to determine the target speed in meters per second.

      (c) Third, the observer can use the reticle pattern in the standard binoculars or the AN/GVS-5 to measure the distance the target moves during a certain time interval. As the target moves across the reticle pattern, the observer measures the number of mils traveled to the nearest 5 mils. He multiplies that number by the OT factor to convert the distance traveled by the target to meters. He divides the distance traveled by the time interval to determine the target speed, in meters per second, and then rounds to the nearest 1 meter.

NOTE: The observer can also designate by using the G/VLLD, binoculars, or AN/GVS-5, a distance on the ground; for example, 100 meters. He then times how long the target takes to travel that distance and divides that distance by the time interval.

    (2) Once the speed and direction are determined, the observer must predict the intercept point. To do this, he first gathers and adds the following information:

  • Total processing time (observer, FDC, and gun times).

  • Time of flight.

    He then multiplies that sum by the target speed. The product is the minimum distance to plot the intercept point in front of the moving target in the direction it is traveling. So the target will not pass the intercept point before the round impacts, the observer must plot the intercept point distance well ahead of the moving target to allow himself enough time to get the grid and prepare his call for fire. Experience dictates how far ahead of the target to plot the intercept point. An untrained observer should add to the intercept distance half the distance determined to allow enough time. More time is better than not enough time. To simplify plotting, the observer can round up the intercept distance to the nearest 100 meters.

NOTE: If, through experience, the observer knows, how long it will take the firing unit to be ready to fire the mission, he should use that time. If not, he should use 200 seconds as the time from the initiation of the call for fire to round impact He converts this time to distance, in meters, and applies the distance in the direction of movement to determine an intercept point as explained above.

EXAMPLE

The distance measured between points A and B by using the G/VLLD is 50 meters.
The time interval between A and B is 10 seconds.
Speed of the target is 50 meters in 10 seconds or 5 meters per second.
Total processing time is 180 seconds (3 minutes).
Time of flight is 20 seconds.
The distance at which to plot the intercept point is 5 meters per second x 200 seconds, or 1,000 meters (See Figure 5-28).

NOTE: Minutes must be converted to seconds for this to work.

Figure 5-28. DETERMINING THE INTERCEPT POINT

    (3) Given the above example, the intercept point must be at least 1,000 meters in front of the target along the intended path of the target. The method of control should be observer control (at my command). The intercept point grid is then used in the call for fire as the target location.

b. Trigger Point. Once the intercept point is determined and the mission is sent to the firing unit, the observer must determine a point at which to "pull the trigger." This trigger point tells the unit when to fire. This point is determined to ensure the rounds and target arrive at the intercept point at the same time. Ideally, the trigger point will be an easily identifiable point. When the target passes over or near the trigger point, the observer commands the guns to fire.

    (1) In choosing a trigger point, the observer must consider the intended path of the target, target speed, time of flight (TOF), and CFF transmission time. If it is a Copperhead mission, the size and shape of the footprint are also considered.

      (a) The first step is to determine the distance from the planned target location or intercept point to the trigger point. This is done by adding the transmission time (an average of 5 seconds) to the time of flight received in the MTO and multiplying this sum by the speed of the target.

EXAMPLE

Time of flight is 20 seconds.
Target speed is 5 meters per second.
Distance to trigger point = (transmission time + TOF) x target speed, or (5 seconds + 20 seconds) x 5 meters per second = 125 meters.

      (b) The trigger point is then plotted by measuring the distance determined above from the planned target location or intercept point along the intended path toward the moving target (Figure 5-29).

    (2) If the target passes the trigger point before the battery reports READY, the observer should make a bold shift to a new target location by using the same trigger point and intercept distances. A grid for the new location should be sent to the FDC immediately.

    (3) If the observer does not intend to request AT MY COMMAND or BY ROUND AT MY COMMAND, the trigger point becomes the point at which he initiates his call for fire. In this case, mission reaction time must be included in determining the distance to the trigger point. Normal mission reaction times are as follows:

  • Priority targets--30 to 60 seconds (plus time of flight).

  • On-call targets--90 to 120 seconds 1 plus time of flight).

  • Targets of opportunity--150 to 180 seconds (plus time of flight).

Figure 5-29. DETERMINING THE TRIGGER POINT

5-14. PLANNED TARGET

A planned target is a target upon which fires are prearranged. The degree of prearrangement varies, but some prior coordination or action is done to facilitate engagement. Planned targets may be further subdivided into scheduled, on-call and priority targets. For more detailed information on planned targets, see FM 6-20-40 and FM 6-20-50.

a. Engaging planned moving targets is basically the same as explained above for engaging targets of opportunity. However, a moving target may change its direction of travel and not travel over the initially planned intercept point. In this case, the observer must select a new intercept point and trigger point and engage the target as a target of opportunity by using the procedures in paragraph 5-13.

b. The planned target location will be the intercept point. As soon as the observer sees the vehicles to be engaged, he must verify their direction and speed of travel and confirm his intercept and trigger point distances by using the procedures in paragraph 5-13. The planned intercept point and trigger point may not allow enough time for total processing time plus time of flight. Then, the observer must determine a new intercept point and a new trigger point and engage the target as a target of opportunity by using the procedures in paragraph 5-13.



HELPFUL NOTES FOR THE OBSERVER

1. Often, initial rounds can be located more quickly with the naked eye than with field glasses. The spotting should be instantaneous and the correction sent immediately to the FDC.

2. For observers who wear glasses, the protective plastic lens cap on the binoculars can be removed to increase the field of vision. Masking tape can be used on the metal retaining ring to prevent scratching the glasses.

3. The diopter adjustment ring can be taped in the correct position so that the observer does not have to adjust the diopter setting every time he uses his binoculars.

4. For adjust fire missions, angular deviations measured with the binoculars are measured to the nearest 5 mils for deviation and 1 mil for HOB.

5. The observer should memorize the width (in mils) of his fingers and hand. Then, when shifts of 100 mils or more are required, he can use his hand instead of binoculars for determining shifts to place fire in the vicinity of the adjusting point as quickly as possible.

6. The OT factor must be applied to obtain corrections for HOB as well as for deviation.

7. A good terrain sketch provides an observer direction and a means for making a good terrain map association.

8. An observer can use the direction and flash-to-bang time of an impacting round to determine its approximate grid location.

9. The observer must take immediate action if communications equipment is not working properly.

10. The importance of accurate initial fires (fire for effect) cannot be overemphasized. The enemy will change posture (dig in or move) if he knows that he is being fired upon.

11. A sketch is a must in determining usable rounds on a precision registration.

12. The OP is not the place to learn procedures for conduct of fire. All procedures should be learned before going to the OP.





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