Military

(1) Verify that the data the range officer gives the OIC apply to the unit firing, that the unit is in the correct location, and that the data are correct. (OIC and safety officer)

(2) Compute and verify the safety diagram (at least two safety-certified personnel. (normally XO or platoon leader and FDO)

(3) Check DA Form 581 (Request for Issue and Turn-in of Ammunition) and the range safety card to ensure that only authorized ammunition is fired. (XO or platoon leader or platoon sergeant)

(4) Ensure that no safety violations occur at or near the weapon(s). (all members of the firing unit)

(5) Check the weapons for correct boresighting. (section chief)

(6) Verify the lay of the battery. (XO, platoon leader, or platoon sergeant)

(7) Compute and verify minimum QE. (XO, platoon leader, or FDO)

(8) Compare minimum QE with the QE for minimum range shown on the safety diagram. Use the larger of the two as the minimum QE. (XO, platoon leader, or FDO)

(9) Verify that the section chief has safety data (safety T). (XO, platoon leader, or platoon sergeant)

(10) Supervise and check the emplacement of safety aids (stakes, tape, and other devices). (XO, platoon leader, platoon sergeant, or gunnery sergeant)

(11) Verify that range clearance has been obtained. (XO, platoon leader, or FDO)

(1) Verify the serviceability of ammunition. (section chief)

(2) Supervise key safety personnel in the performance of their duties. (OIC or safety officer)

(3) Verify that the charges, projectiles, and fuzes being fired are only those prescribed on the safety card. (section chief, XO, platoon leader, or platoon sergeant)

(4) Verify that rounds are not fired below the minimum QE or above the maximum QE. (section chief, XO, platoon leader, or platoon sergeant)

(5) Verify that rounds are not fired outside the lateral (deflection) safety limits specified on the safety card. (section chief, XO, platoon leader, or platoon sergeant)

(6) Verify that time-fuzed rounds are not fired with fuze settings that are less than the minimum time prescribed on the safety T. (section chief, XO, platoon leader, or platoon sergeant)

(7) On all commands that are unsafe to fire, command CHECK FIRING and give the reason(s) why the command(s) is(are) unsafe. (any person)

(8) Recompute and issue updated safety Ts under the following conditions: (FDO or chief computer)

• When a registration is completed.
• When met conditions change.

(9) Suspend firing when any unsafe condition exists. (Any person who sees an unsafe act) Examples of unsafe conditions areas follows:

• Powder bags exposed to fire.
• Personnel smoking near pieces or ammunition.
• Improper handling of ammunition.
• Time fuze previously set and not reset to safe.
• Personnel or aircraft directly in front of the weapon.
• Primer inserted into the firing assembly before the breech is closed (separate-loading ammunition).
• Failure to inspect the powder chamber and bore after each round is fired.
• Failure to swab powder chamber after each round of separate-loading ammunition is fired.

(1) For deflection safety aids--

• Set off the left deflection limit on the pantel by using the deflection counter. Traverse the tube to establish the proper sight picture on the aiming point.
• Emplace the safety stake against the right side of the lunette, and drive it firmly into the ground.
• Mark the right deflection limit in the same manner, but emplace the safety stake on the left side of the lunette.

(2) For QE safety aids--

• Use the cam follower as an index mark.
• Set off the maximum QE on the fire control quadrant. Elevate the tube until the bubbles center in the elevation level vials.
• Mark the cam with apiece of tape in line with the cam follower.
• Mark the minimum QE in the same manner.

(1) For deflection safety aids--

• Determine the left deflection limit. Set off the left deflection limit on the pantel by using the deflection counter.
• Traverse the tube to the left as much as possible.
• Traverse the carriage (shift trails) until the correct left deflection limit sight picture on the aiming point is established.
• Place a left limit safety stake against the right side of the spade.
• Mark the right deflection limit in the same manner, but emplace the safety stake on the left side of the spade.

(2) For quadrant elevation aids--

• Use the stationary bracket on the elevation gear box as an index mark.
• Set off the maximum QE on the fire control quadrant. Elevate the tube until the bubbles center in the elevation level vials.
• Mark the elevation arc with a piece of tape in line with the stationary bracket on the elevation gear box.
• Mark the minimum QE in the same manner.

(1) For deflection safety aids--

• With the tube parallel to the azimuth of lay, place a piece of tape over the azimuth counter (bottom carriage).

• Set off the left deflection limit on the pantel by using the deflection counter. Traverse the tube to establish the proper sight picture on the aiming point.
• Using a straight edge, draw a line on the tape placed on the bottom carriage directly below the azimuth counter index mark found on the upper carriage. Record the left deflection limit next to that line.
• Mark the right deflection limit in the same manner.

(2) For quadrant elevation safety aids--

• With the tube elevated to 0 mils, place a piece of tape on the trunnion support and draw a straight line as an index.
• Set off the minimum QE on the fire control quadrant. Elevate the tube until the bubble centers in the elevation level vial.
• Place a piece of tape on the quadrant mount, and draw a line across from the index line established on the trunnion support. Record the minimum QE next to that line.
• Mark the maximum QE in the same manner.

(1) Deflection safety aids. These may be marked on the exterior and/or interior of the hull.

• Make an index mark on the top carriage with a piece of tape.

• Set off the left deflection limit on the pantel by using the reset counter. Traverse the tube to establish a proper sight picture on the aiming point.

• Place a piece of tape on the bottom of the carriage directly under the index mark.

• Mark the right deflection limit in the same manner.

(2) Quadrant elevation safety aids. These may be marked on the exterior or the interior of the weapon. To emplace the safety aids on the interior of the weapon, follow the steps in paragraph c(2) above. To mark the exterior of the weapon, perform the following steps:

• Mark an index on the tube with a piece of tape.
• Set off the maximum QE on the fire control quadrant. Elevate the tube until the bubble centers in the elevation level vial.
• Place a mark on the top carriage in line with the index mark.
• Mark the minimum QE in the same manner.

a. The FDO, on receipt of the safety card, constructs a basic safety diagram. The basic safety diagram is a graphical portrayal of the data on the safety card or is determined from the surface danger zone (AR 385-63, Chapter 11) and need not be drawn to scale. Shown on the basic safety diagram are the minimum and maximum range lines; the left, right, and intermediate (if any) azimuth limits; the deflections corresponding to the azimuth limits; and the azimuth of lay.

b. The steps for constructing a basic safety diagram are shown in table 15-2. An example of a completed safety diagram is shown in Figure 15-2.

c. When the basic safety diagram is complete, it will be constructed to scale, in red, on the firing chart. Plot the firing point location as listed on the range safety card. Using temporary azimuth indexes, an RDP, and a red pencil to draw the outline of the basic safety diagram. To do this, first draw the azimuth limits to include doglegs. Then, by holding the red pencil firmly against the RDP at the appropriate ranges, connect the azimuth lines.

d. Only after drawing the basic safety diagram on the firing chart may the base piece location be plotted and deflection indexes be constructed. Should the diagram be drawn from the base piece location, it would be invalid unless the base piece was located over the firing point marker.

e. After the basic safety diagram has been drawn on a sheet of paper and on the firing chart, it is drawn on a map of the impact area using an RDP and a pencil. These limits must be drawn accurately, because they will be used to determine altitudes for vertical intervals. Determine the maximum altitude along the minimum range line. This is used to ensure that the quadrant fired will cause the round to clear the highest point along the minimum range line and impact (function) within the impact area. At the maximum range, select the minimum altitude to ensure that the round will not clear the lowest point along the maximum range. Once the altitudes have been selected, label the basic safety diagram with the altitudes for the given ranges.

a. The safety T is a convenient method of arranging safety data and is used to verify the safety of fire commands (Figure 15-5). The information needed by the FDO, XO, or platoon leader, and section chief is organized in an easy to read format. The safety T is labeled with a minimum of firing point location, charge, projectiles(s), fuze(s), angle of fire, and AOL. Other optional entries are subject to unit SOP. Any time new safety data are determined, new safety Ts are constructed and issued only after the old safety Ts have been collected (that is, after a move or after a registration or MET + VE). Use only one charge per Safety T. (Note: The examples in this demonstrate which data is transferred from the Safety Matrix to the Safety Tee. This data is in bold type in the matrix and the associated safety T).

b. It is the FDO's responsibility to ensure that all data transmitted from the FDC is within the limits of the safety T. It is the section chief's responsibility to ensure that all data applied to the ammunition or howitzer is within the limits of the safety T. The FDO must ensure that deflection to fire is between the deflections listed on the safety T. He then must determine if the quadrant elevation corresponding to that deflection is between the minimum and maximum QE on the safety T. Finally, he must ensure that the fuze setting is equal to or greater than the minimum fuze setting listed on the safety T for the specific fuze type.

a. After a GFT setting is determined (result of registration or MET + VE technique), the

FDO must compute new safety data. The GFT setting represents all nonstandard conditions in effect at the time the GFT setting was determined (Chapter 10 and 11 discuss Total Corrections in detail). The effect on safety is that the data determined before the GFT setting was determined no longer represent the safety box, and could result in an unsafe condition if not applied to safety computations. In order to update safety, new elevations are determined which correspond to the minimum and maximum ranges. Deflections are modified by applying the GFT deflection correction to each lateral limit. Minimum fuze settings are also recomputed. The basic safety diagram drawn in red on the firing chart does not change. It was drawn on the basis of azimuths and ranges, and it represents the actual limits.

b. There are two techniques which can be used to update safety computations: The

Range K Method and Applying a GFT setting to a GFT. Both methods use the same safety matrices, and apply to both low and high angle fire. The preferred technique for updating safety is to apply a GFT setting to the appropriate GFT. Unfortunately, not all munitions have associated GFTs. Application of Total Corrections is the same as for normal mission processing. The Total Corrections, in the form of a GFT setting or Range K, must be applied in accordance with the data on which they were determined (i.e., the GFT setting for a HE registration applies to all projectiles in the HE family, while a MET + VE for DPICM would apply to all projectiles in the DPICM family). If automation is available a false registration with M795 graze burst data may be used to determine total corrections for all projectiles in the DPICM family (see ST 6-40-2 for procedures). The principle difference between the two techniques is the manner in which minimum fuze setting is determined.

a. Copperhead safety data are determined from ballistic data developed specifically for the Copperhead projectile. Computations are much like those for normal projectiles. The Copperhead round should never be fired with standard data. Therefore, the computation of safety data requires the solving of a Copperhead Met to Target technique for each listed range using the FT 155-AS-1, as covered in Chapter 13, Section 1. See Table 15-7 for steps to compute Copperhead safety. Surface Danger Zones (SDZs) for shell Copperhead are significantly different than normal indirect fire SDZs. AR 385-63 (MCO P3570), chapter 11, contains the SDZs for Copperhead.

b. All ranges listed on the range safety card may not fall within the ranges listed in the TFT charge selection table for that charge and mode. Therefore, additional safety computations may be required for additional charge(s) and mode(s) to adequately cover the impact area. If ranges listed on the range safety card overlap charge and mode range limitations in the charge selection table, then safety for both affected charges and modes must be computed.

a. The safety data for high angle fire is computed in much the same manner as that for low angle fire except for the ballistic variations caused by the high trajectory. Site is computed differently (by using the 10 mil Site Factor and the Angle of Site/10), and mechanical or electronic fuze settings are not determined. (Note: It is the FDO's responsibility to ensure that all High Angle Fuze Settings will cause the fuze to function within the safety box). Table 15-8 contains the steps required for computation of High Angle Safety.

b. Use the steps outlined in Table 15-8 and in the matrix in Figure 15-12 as examples for organizing computations. The High Angle Safety Matrix is used for all munitions except M712 CLGP (Copperhead). The data are determined by either graphical or tabular firing tables. In the case of expelling charge munitions, the Safety Table located in the Firing Tables or Firing Table Addendums is utilized to determine Elevation, Time of Flight, Fuze Setting, and Drift. (Note: The Safety Tables which are used to compute the High Angle examples are located after the Low Angle Safety examples). Use artillery expression for all computations except where noted.

a. Piece-to-crest range (PCR) is the horizontal distance between the piece and the crest, expressed to the nearest 100 meters. Procedures for measurement are discussed in paragraph 15-16.

b. Angle 1 (Figure 15-18) is the angle of site to crest measured by the weapons. See paragraph 15-16 for procedures.

c. Angle 2 (Figure 15-18) is the vertical angle required to clear the top of the crest. For quick, time, and unarmed proximity (VT) fuzes, a vertical clearance of 5 meters is used. For armed VT fuzes, see paragraph 15-19.

d. Angle 3 (Figure 15-18) is the complementary angle of site. It is the complementary site factor (TFT, Table G) for the appropriate charge at the piece to crest range mulitiplied by the sum of angles 1 and 2. Site is the sum of angles 1, 2, and 3.

e. Angle 4 (Figure 15-18) is the elevation (TFT, Table F) for the appropriate charge corresponding to the PCR.

f. Angle 5 (Figure 15-18) is a safety factor equivalent to the value of 2 forks (TFT, Table F) for the appropriate charge at the PCR.

g. The sum of angles 1 through 5 (Figure 15-18) is the minimum QE for the weapon and the charge computed.

a. There are five methods that can be used to measure piece-to-crest range:

b. Regarless of the method used to measure PCR, the XO or platoon leader must verify PCR before he computes QE. He can do this by using any of the five methods.

a. The XO or platoon leader does the computations indicated in this section if the sum of angles 1 and 2 (Figure 15-18) exceeds 300 mils or if the rapid firing tables (RFTs) are not available. All angles are determined and expressed to the next higher mil. Table 15-9 lists the steps and solves an example of an XO's or platoon leader's manual computations.

b. The same example is solved in Table 15-10 by using RFTs in the ST 6-50-20, Appendix B.

c. One howitzer section may report a site to crest that is unusually high. If the XO or platoon leader determines that it is the result of a single narrow obstruction (such as a tree), the piece can be called out of action when firing a deflection that would engage the obstruction. This would enable the platoon to use the next lower site to crest. Other alternatives are to remove the obstruction or move the weapon.

d. Table 15-11 illustrates why minimum QE is computed for all guns, regardless of which has the largest site to crest.

a. The method of computing the XO's minimum QE for firing a projectile fuzed with an M728 or M732 fuze depends on the method in which the fuze is used. The proximity (VT) fuze is designed to arm 3 seconds before the time set on the fuze; however, some VT fuzes have armed as early as 5.5 seconds before the time set on the fuze. Because of the probability of premature arming, a safety factor of 5.5 seconds is added to the time of flight to the PCR. Since time on the setting ring is set to the whole second, the time determined in computing minimum safe time is expressed up to the nearest whole second. A VT fuze is designed so that it will not arm earlier than 2 seconds into its time of flight, which makes it a bore-safe fuze.

b. In noncombat situations, the XO or platoon leader determines the minimum safe time by adding 5.5 seconds to the time of flight to the minimum range line as shown on the range safety card. The minimum QE determined for fuzes quick and time is also valid for fuze VT.

c. In combat situations, the XO or platoon leader determines the minimum QE and a minimum safe time for fuze VT. The minimum QE determined for PD fuzes is safe for VT fuzes if the fuze setting to be fired equals or is greater than the minimum safe time determined in paragraph a above. If the XO or platoon leader finds it necessary to fire a VT fuze with a time less than the minimum safe time, he must modify the minimum QE. He does this by increasing the vertical clearance to ensure that the fuze will not function as it passes over the crest. In addition, he must ensure the fuze will not function over any intervening crests along the gun-target line (See paragraph 15-21).

d. If the projectile is to be fired with the VT fuze set at a time less than the minimum safe time, allowance must be made for vertical clearance of the crest. Vertical crest clearances for armed M728 and M732 VT fuzes fired over ordinary terrain for all howitzer systems is 70 meters.

e. If the projectile is to be fired over marshy or wet terrain, the average height of burst will increase. The vertical clearance is increased to 105 meters. If the projectile is fired over water, snow, or ice, the vertical clearance is 140 meters.

f. The minimum QE for armed fuze VT when a fuze setting less than the minimum safe time is fired is based on the piece-to-crest range and a vertical clearance as indicated in paragraphs d and e above.

g. Figure 15-19 shows a decision tree for application of armed VT minimum QE.

h. Table 15-12 is an example of computations to determine minimum QE for an armed VT fuze.

i. The same example is solved in Table 15-13 by using the RFT in the ST 6-50-20, Appendix A.

j. If the VT fuze setting to be fired is equal to or greater than the minimum safe VT time, the minimum QE for fuzes quick and time applies. If the VT fuze setting to be fired is less than the minimum safe VT time, the minimum QE determined for armed VT applies.

b. Option 1 is preferred because it incorporates all current nonstandard conditions that will affect the projectile along the trajectory. The FDO has the responsibility to determine on the basis of availability of corrections for nonstandard conditions if this really is the best option. Table 15-12 lists the steps.

c. Option 2 does not include current conditions for all nonstandard conditions. Table 15-15 lists the steps.

d. The least preferred option is using the trajectory charts in the appendix of the TFT. This offers a quicker but less accurate method to clear the intervening crest since it is based off of standard conditions. The FDO must make a judgment call when to use these charts. The FDO must use caution when making this decision.