ATP-3-09-30 Observed Fires Download
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Adjustment of Fire 28 September 2017 ATP 3-09.30 5-21 Figure 5-12. Mortar registration Adjusting the Sheaf for Mortars 5-79. One additional step that is not required for artillery but may be required for mortars is adjusting the sheaf. Adjusting the sheaf may occur anytime during a fire mission or the FDC may direct it 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. Mortars are positioned with tubes numbered (for example, one through four for an 81-mm platoon) from right to left as seen from behind the tubes. If a mortar platoon has six tubes, the tubes will be numbered one through six when employed as a platoon or one through three when employed by sections. 5-80. To start adjustment of the sheaf, the observer requests SECTION RIGHT (or LEFT) REPEAT, OVER. The method of fire is determined based on the wind direction. If there is a left cross wind, then the observer would direct SECTION RIGHT REPEAT, OVER. The purpose of this is so that the subsequent rounds are not obscured by dust blowing from the previous explosions. (Figure 5-13 on page 5-22) for a 120- mm section, numbers one and three will fire (in that order). (Number two conducted the registration.) 5-81. 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, ignore range corrections for rounds impacting within 50 meters of the sheaf. The sheaf is adjusted perpendicular to the gun-target line. (If angle T is greater than 500 mils, adjust each piece onto the registration point. The FDC computes data for the sheaf.) Make lateral refinement corrections to the nearest 10 meters, but do not fire corrections of less than 50 meters. Once refinement corrections for all mortars have been determined, adjust the sheaf. Figure 5-12 shows an adjusted sheaf for an 81-mm section.