Military

(1) Firing coordinated missions. The FDC and FO coordinate the location of the RP before the FO joins the unit to support it. Once the FO is in position, the FDC sends a message telling the FO to prepare to register RP 1. The FO sends the OT direction to the RP.

(2) Firing noncoordinated missions. The FO, upon joining the unit to support it, checks the area of responsibility and selects a point to be used as the RP. This point must be identifiable both on the ground and on the map to allow a valid eight-digit grid to be determined. The FO then sends the call for fire to register the RP.

(1) To obtain the DOF after constructing the chart, align the mortar position with the RP. Determine the DOF to the nearest mil.

(2) To determine the mounting azimuth, round off the DOF to the nearest 50 mils.

(3) To superimpose the deflection scale, the referred deflection is received from the section sergeant. Then, construct the deflection scale in the same manner as for the modified-observed chart.

(4) Determine correction factors after the registration has been completed. Apply these factors to all other targets within the transfer limits of the RP.

(1) Range correction factor. The RCF is the number of meters per thousand to be applied to the initial chart range of a target within the transfer limits resulting in a range correction for that mission. Continuing the preceding example, since the ranges to other targets will not be 3,050 (range to RP), the RCF (+150) will not be correct. Therefore, other range corrections must be determined and used for other targets. Once the range difference has been determined, round the initial chart range to the nearest 100 and then express that in thousandths.

(2) Deflection correction. The deflection correction is the number of mils needed to correct the deflection to hit the target since nonstandard conditions again caused the plots on the board to be either left or right of the initial chart deflection (Figure 14-6). Compare the initial chart deflection and the final chart deflection and subtract the smaller from the larger.

RULE: Final chart deflection (hit) larger = LEFT deflection correction; final chart deflection (hit) smaller = RIGHT deflection correction.

(1) Range correction. Determine the initial chart range, then round to the nearest hundred and express it in thousandths; for example, 2975 = 3000 = 3.0. Multiply the range in thousandths times the RCF and use the sign of the RCF: 3.0 x +48 = +144. This gives the total range correction for this target.

(2) Total range correction. The total range correction (TRC) is the total correction that must be applied to get the command range to fire the target. TRC is the range correction (RCF x range in thousandths) plus or minus the altitude correction.

(1) Fire the reregistration at the established RP using only the mortar that originally fired the registration (Figure 14-7). (The FDC assumes that the sheaf is still parallel; therefore, the sheaf should not need adjusting again.) The chart data are the same as with the initial registration. Apply the firing corrections to obtain the command data (Figure 14-8). (A blank reproducible copy of DA Form 2188-R, Data Sheet, is located at the back of this manual.)

(2) The chart deflection plus or minus deflection correction equals command deflection. The chart range plus or minus the range correction plus or minus the altitude correction equals the command range.

(3) Carry out the mission the same as with the initial registration. Once the EOM, "Registration complete," has been given, determine firing corrections again.

(4) In the initial registration, the FDC compared the initial chart range and the final chart range difference. Determining the range difference after the reregistration is the same; however, now determine the final adjusted range. During the reregistration, firing corrections were applied for each round. Now apply those same corrections.

(5) Adjusted range is the final range with the correction for altitude correction deleted.

(6) Once the final adjusted range has been determined, compare the initial chart and the final adjusted range. Subtract the smaller from the larger to determine the RCF. The sign (+/-) would be determined as with the initial registration. Again, divide the range (initial chart range rounded to the nearest 100 expressed in thousandths) into the new range correction to determine the new RCF.

(7) To determine the deflection correction, compare the initial chart deflection and the final command deflection. Subtract the smaller from the larger and determine the sign (L or R) to apply.

(8) Apply the new firing corrections to all targets that have been and are fired within the transfer limits. For those targets that are already plotted on the board, apply the new firing corrections and update the target data. (The chart data do not change. The target has not moved; only the weather has changed.)

(1) Set up the M16/M19 plotting board as a surveyed firing chart (eight-digit grids to the mortar position and RP).

(2) Plot the location and altitudes of the two FO points to be used.

(3) Record all data on DA Form 2188-R. To determine each FO's direction to the RP, rotate the azimuth disk until the FO's position is aligned with the RP. Read the azimuth scale to the nearest mil. To determine each FO's vertical angle, compare the altitudes of each FO's location and the RP, and subtract the smaller from the larger. This remainder is the VI, which is used to determine the vertical angle and carries the sign of the larger. Determine the range from each FO's location. Round the range to the nearest 100 and express it in thousandths. Divide the range expressed in thousandths into the VI and determine the product to the nearest whole mil. The sign (+/-) of the vertical angle (VA) is the same as the VI sign (+/-).

(4) To determine the firing data, align the mortar position with the RP. Determine the chart data and apply the range correction for altitude between the mortar and target. During the registration, only the range correction for altitude is used. Give the firing command to the base mortar. Three to six rounds will be fired at 10-second to 20-second intervals. The FO uses this interval to give himself time to determine the azimuth readings to each round. If the azimuth for one or more rounds is determined to be 50 or more mils different, then another round may be fired for each erratic round. Six rounds are needed for the most accurate MPI registration, but as few as three rounds give correction data.

(5) As the rounds are fired, the FO reads the azimuth to each round and records it. When the last round has been fired, he sends the data recorded to the FDC. Once the rounds have been fired and the readings recorded in the FDC, plot the MPI as follows:

(1) Range difference. Compare the command range to the MPI point (minus the altitude correction) and the initial chart range to the RP.

(2) Range correction factor. Once the range difference has been determined, divide it by the chart range to the MPI rounded to the nearest 100 expressed in thousandths and round it to the nearest whole meter. The sign is the same as the range difference.

(3) Deflection correction. Compare the chart deflection of the MPI and the chart deflection of the RP (Figure 14-9) to determine the deflection correction. The sign of the deflection correction will be determined by how the move from the MPI to the RP must be made.

(1) Grid missions. The target is plotted on the map and the altitude determined. If the altitude of the target cannot be determined, then the computer assumes that it is the same as that of the mortars.

(2) Shift missions. The target is assumed to be the same altitude as the point being shifted from unless, in the call for fire, the FO sends a vertical shift (up or down). Therefore, that shift is applied to the point being shifted from, and that is the altitude of the new target.

(3) Polar missions. The altitude of the target is assumed to be the same as that of the FO's position if no vertical shift is given. If one is given, then the computer applies the shift to the FO's altitude, and that is the altitude of the new target. Once the computer has determined the altitude of the target, then it is possible to determine the VI for the mission and, finally, the altitude correction to apply. Remember, VI is the difference in altitude between the mortars and the target.

(1) When the first round impacts, the radar operator sends the FDC the direction and distance to that round.

(2) The FDC then indexes that direction and plots the round at the distance sent (the plot is made from the radar position plot, using the distance sent).

(3) The FDC indexes the mortar RP azimuth and determines the spotting by comparing the round's impact plot with the RP plot. The FDC, acting as the FO, determines all spottings (Figure 14-11).

(4) Once the spotting has been determined, the FDC converts the spotting into a correction to fire the second round. He does this by reversing the signs of the spotting. He then applies that to the registration point on the azimuth of the radar position (Figure 14-12).

(5) The firing data are then obtained by aligning the new plot with the mortar position.

(6) The spottings for additional rounds are spotted from the initial RP, but the corrections (spotting reversed) are applied to the last fired plot. This procedure is repeated for all adjustment rounds until a range correction of 50 meters is split.

(1) Adjust each mortar onto the FPF (most desirable method).

(2) Adjust only the danger-close mortar, using the attitude of the target and mortar position to compute data for the other mortars.

(3) Using the attitude of both the mortar section and the FPF, compute only the data for the FPF, with no rounds being fired (least desirable method).

(1) Once the danger mortar is known (Figure 14-13), it is adjusted onto the FPF line.

(2) Once the danger mortar has been adjusted, the next mortar (No. 2) is given the danger mortar data and fired. The firing of the same data should put the impact of the next mortar 40 meters left or right of the adjusted mortar.

(3) This procedure is used for the remaining mortars until each is on the FPF line. As each mortar is adjusted to the FPF line, the data are then given to each mortar and placed on the mortar after each mission. Also, the predetermined number (unit SOP) of rounds are set aside ready to fire (Figure 14-14).

(1) The FDC can determine the danger-close mortar by indexing the target attitude and drawing a line from the initial FPF plot (given in the call for fire) 50 meters above and below (Figure 14-15).

(2) After drawing the FPF line, the computer rotates the azimuth disk and aligns the mortar plot with the FPF plot to see which side of the line is closest to the friendly troops (Figure 14-16).

(3) After the danger mortar is adjusted to the FPF line, the computer then indexes the FPF attitude and erases all but the last plot.

(4) Using the last plot, the computer draws the FPF symbol by extending a line 90 meters long toward the top of the board and 10 meters long from the plot towards the bottom of the board. This shows the full 100-meter width of the FPF.

(5) The remaining plots for the No. 1, No. 2, and No. 3 mortars are then plotted 40 meters apart (Figure 14-17).

(6) Once the plots are on the plotting board, the computer determines the firing data for each mortar by aligning each mortar plot with its intended impact plot (Figure 14-18).

(7) Again, these data are placed on the mortar after each mission, and the rounds are readied to fire.

(1) The computer then indexes the attitude of the mortar section and plots the No. 1, No. 3, and No. 4 mortars 40 meters above and below the No. 2 mortar plot.

(2) Once the FPF and mortars have been plotted, each mortar is aligned with its impact plot, and the data determined.

(3) These data are given to the mortars and, again, are set on the mortars between missions.

(4) This method is used when ammunition is low and time or the tactical situation does not permit the adjustment of the FPF.