The XO announces fire commands to the adjusting piece to fire the initial round in the mission. The FDC announces the remaining commands by voice. Normally, the howitzer back-lay method of lay will be used during an emergency fire mission. It should only be used if the grid azimuth and aiming point-deflection methods are not possible. An M2 compass and an aiming circle are the only equipment needle. Ensure the aiming circle is emplaced in the left rear of the position area.
With the lower motion, he sights on the pantel of the adjusting piece. The line on the aiming circle is now parallel to the howitzer tube after firing the first round.
Note: Normally only one deflection will be read to each howitzer, and the piece is laid. The firing platoon receives an emergency fire mission while en route to a new position and signals the convoy. He determines the azimuth of fire and the initial firing data using the BCS emergency fire mission procedures.
He gives this information to the FDO and the platoon leader. Upon occupation of the position, the platoon leader aligns his vehicle in the general direction of fire. The platoon leader then marks the azimuth of fire for the adjusting piece by using a strip of engineer tape approximately the same length as the weapon system.
This tape should have a wooden stake on one end and a nose plug on the other end. To mark the azimuth, the platoon leader throws the nose plug in the direction of the azimuth of fire. Then, using the M2 compass, he aligns the tape on the azimuth of fire by moving the stake end of the tape. At the same time the platoon leader is marking the azimuth, these other actions are taking place:. The platoon sergeant takes the aiming circle to the left flank of the firing position. He ensures he has moved far enough to the left rear of the weapons so that he is beyond the point where the left flank howitzer will be positioned.
He then sets up the aiming circle, levels it, and is prepared to accept a referred deflection from the adjusting piece. The chief computer positions the FDC vehicle so that the rear of the vehicle is facing the gun line. This allows the FDC to observe the state of readiness of the firing sections and announce voice fire commands. The platoon leader quickly guides the adjusting piece into position where the engineer tape is aligned along the azimuth of fire.
Self-propelled weapons drive alongside the line, while towed howitzers are brought in from the direction of fire and centered over the tape. The adjusting piece is laid on the target as soon as it is aligned on the engineer tape.
The FDC has provided firing data charge and quadrant to the platoon leader. These are announced to the adjusting piece, and the first round is fired. The gunner establishes an aiming point. As the adjusting piece is preparing to fire the first round, all other howitzers are pulling on line. Positioning is critical. Each chief of section must position his howitzer so that his gunner can seethe aiming circle and where the line of sight is not impaired for any other howitzer.
Upon hearing the above comment, the gunner-- - Using the azimuth knob, without moving the tube, rotates the head of the pantel and sights on the instrument or object. Note: When referring to the second circle to verify initial lay, the gunner must ensure that the tube is on the azimuth of fire before he uses the above procedures. The platoon sergeant sets the referred deflection on the upper motion of the aiming circle and with the lower motion, sights on the pantel of the adjusting piece.
The platoon sergeant is now ready to lay the remaining pieces of the platoon. Each gunner identifies the aiming point and receives his deflection. The deflection is set off, the tube traversed until his line of sight is back on the aiming circle, and the piece is laid.
In the interest of time, there normally are no rechecks. If the initial target location was good and if the platoon leader accurately laid out the azimuth tape, the second volley may well be fire for effect.
An aiming point is established for each weapon. The platoon sergeant should remain at the aiming circle during the firing of the mission in case a weapon must be re-laid or the lay of the platoon needs to be refined.
The platoon leader, using his M2 compass, should visually check the gun line to ensure that there is no gross error in the lay of the weapons. The deflection at which the aiming points are established is recorded by each gunner. The direction in which the battery is initially laid and the corresponding common deflection are used as references from which the FDC can derive firing deflections for future targets. Note: For further discussion on aiming points, see paragraph D The collimator is the primary aiming point and is placed 4 to 15 meters from the sight of the weapon.
When the collimator is emplaced, 3 numbers 5, 0, 5 and 11 graduations will be visible in the reticle. If possible, place the collimator under cover to the left front or left rear of the weapon. See Figure for the proper sight picture. When aiming posts are used, the far aiming post should be placed meters from the howitzer and the near aiming post should be placed 50 meters from the howitzer.
If the situation or terrain limits placing the far aiming post meters from the howitzer, place it out as far as possible and place the near aiming post halfway between the howitzer and the far aiming post. As soon as the platoon is laid and the aiming point s is are emplaced, the platoon leader should have the gunners of all pieces refer to a distant aiming point if one is available.
A DAP must be at least 1, meters away. This DAP can be used as the primary aiming point if something happens to the collimator or aiming posts. Close-in aiming points are moveable, established by battery personnel, and can be seen at night. The DAP has the advantage of being readily available upon occupation of a firing position.
During an emergency occupation, it is recommended that a distant aiming point be selected. If a DAP is not available, then several other options can be used. Two examples are as follows:. Set up the collimator. Set up an aiming post at a point halfway between the aiming circle and the pantel.
Safety and verification of tasks by leaders are disciplines that exist in the field artillery, regardless of whether operations are performed in combat or in peacetime. For every task that is performed, there is another person in a leadership position section chief, platoon sergeant, platoon leader or XO, FDO, or BC who verifies the accuracy of the action performed, This system of double checks is inherent in all operations and is not to be considered a limiting factor in providing timely fire support.
Therefore, commanders must ensure that their units have a system of independent safety checks. These checks ensure that all cannon battery and platoon operations for example, FDC mission processing and orienting howitzers for direction affecting firing is checked by someone other than the person who performs the action.
Though most independent checks take place before missions are received, performing independent checks is a continuous process and must be rigidly enforced to ensure fires are timely, accurate, and safe.
These checks may include, but are not limited to, the following:. Verification of target grid. Verification of battery or platoon lay. Verification of weapon location. Verification of met data. During a deliberate occupation, the lay of a unit is verified immediately following the verification or conduct of boresighting. The unit SOPs will specify the method and sequence of verifying lay during an emergency occupation.
After the platoon is laid, the platoon leader verifies the lay by use of another M2A2 aiming circle referred to as the verification circle. To verify lay of the platoon, the following steps are taken:. However, in combat situations, the BC may authorize the orientation of the verification circle using the same method as the lay circle, METT-T dependent. This aiming circle must be located where it can be seen by all howitzers and should not be any closer than 10 meters to the lay circle.
The lay circle operator will sight his instrument onto the verification circle by use of the recording motion. With the lower motion, he sights back on the lay circle. This serves to align the line of the verification circle parallel to the line of the lay circle. Note: When an aiming circle is used to verify another aiming circle for direction, the readings between the two circle will be 3, mils apart Figure This is because both circles measure horizontal clockwise angles from the line of fire.
To prevent confusion remember that, if you see red, read red. All gunners refer and announce the deflection to the verification circle. If the deflection referred by a howitzer is within that tolerance given in the local range regulations, the operator on the verification circle announces that the howitzer is safe.
Note: When referring to the verification circle to verify lay, the gunner must ensure that the tube is on the azimuth of fire before he uses the above procedures. The platoon leader should walk the gun line and visually check the tubes to ensure they are parallel. An M2 compass should also be used to ensure the tubes are on the azimuth of fire. Normally, vertical angles VAs from the M2A2 aiming circle to the howitzers are measured during advance party operations. The aiming circle can also be used to determine sight to crest at each howitzer during advance party operations.
The VA to a point is measured from the horizontal plane passing through the horizontal axis of the instrument M2A2 aiming circle. It is expressed as plus or minus, depending on whether the point is above plus or below minus the horizontal plane.
It is measured to the height of instrument which is about chest high on the average individual at the gun position. The steps for measuring a VA are as follows:. This yields a correction factor to be applied to all measured vertical angles. If black numbers are used, the correction factor is plus; if red numbers are used, the correction factor is minus. The subtense method is described in paragraph a. Note: If there was not enough time to measure VAs during advance party operations, the instrument operator can align the horizontal cross hair at chest level of a cannoneer during occupation.
The key is to measure the VA at a height that approximates instrument height. The result is the vertical angle for that howitzer. The accuracy of lay is directly related to the method used to orient the howitzers on the azimuth of fire and the alignment of the fire control equipment.
Measuring and reporting data provides us with a method of correction for errors in the lay. The FDC may require a check of weapon direction be made. Normally this check is made after a registration or after survey control is established. It serves to Check the data fired. Check the accuracy of lay. Weapon direction may be verified by. Reporting the correct deflection. Measuring the azimuth.
Measuring the orienting angle. Reporting will reveal any sloppy procedures being used by the gun crews, such as failure to level the bubbles and improper sight picture. Measuring provides a check on the accuracy of the lay. The backward azimuth rule is a mathematical relationship used to apply equal changes in angles used in the laying process. This rule establishes the relationship between three elements as follows:. An increase in deflection causes an equal decrease in azimuth and an equal increase in orienting angle.
A decrease in deflection causes an equal increase in azimuth and an equal decrease in orienting angle. Using this rule and assuming that there are no errors in the lay of the weapons, weapon direction may be verified. To report, the XO or platoon leader Goes to the weapon. Checks the level of the bubbles centers if necessary. Checks for the correct sight picture corrects if necessary. Reads the deflection from the pantel.
When making corrections to the sight picture or leveling the bubbles, the tube must not be moved. Your platoon MA3, mm SP is laid on azimuth orienting angle , with a common deflection of After firing a registration, FDC requests that the platoon leader report the azimuth or orienting angle. He then does the following:. Determines the change between the common deflection and the correct deflection. Applies the difference according to the backwards azimuth rule to determine the azimuth fired.
If a gun fires out of safe, the platoon leader or XO may wish to determine the azimuth at which the round was fired. This is the most common reason for measuring the azimuth of the line of fire. Another reason is that a unit may use a less desirable method of lay and then improve this method. An example would be a unit that lays by the grid azimuth method because there is no survey control.
When survey closes, the unit will want to know if the azimuth of fire it has been firing on is different from the originally intended azimuth of fire.
There are two methods of measuring the azimuth of the line of fire. The difference depends upon whether or not survey control is available. If the line of fire is being measured following a firing incident, the crew of the howitzer in question will not move the tube but will simply refer to the aiming circle.
If, on the other hand, the platoon leader wishes to measure the azimuth of fire, he must first ensure that the tube of the howitzer being measured is at lay deflection. These steps are performed first, regardless of whether or not survey control is available:. Orients the line generally parallel to the tube of the weapon. Note: Memory aids for measuring and reporting are in tables through Sets the announced deflection off on the upper recording motion of the aiming circle.
Note: If the weapon has an Mseries sight, the referred deflection may have to be set on the aiming circle by using the red numbers. A general rule is that if a weapon with an Mseries sight is left and forward of the aiming circle, red numbers are used when reading the aiming circle to lay the howitzer. With the lower nonrecording motion, sights in on the panoramic telescope.
Note: The line of the aiming circle is now parallel to the tube of the firing weapon. If it is not available, follow the steps in subparagraph d below. If it is available, follow those in subparagraph e below. Note: Since the magnetic needle is being used, the aiming circle must be declinated and set up away from magnetic attractions.
Subtract the instrument reading from the declination constant. The difference is the azimuth of the line of fire az of the LOF. For a memory aid, see Table Your M platoon conducted an emergency occupation using the howitzer backlay method to lay on an azimuth of fire of You were instructed to stay in position and continue answering calls for fire.
The platoon is at end of mission, and all howitzers have returned to their lay deflections. You go to the aiming circle and measure an instrument reading of The aiming circle has a declination constant of Your final step is to solve for the azimuth of the line of fire.
Your platoon howitzers were initially laid on , but your BCS or LCU currently has an azimuth of fire entry of You have two options at this point:. Leave the platoon laid on , and have the FDC correct the computer entries for azimuth of fire and piece locations. Re-lay the platoon on the originally intended azimuth of Note: The first option requires less time and effort and is thus normally preferred if the tubes were laid parallel.
However, if the unit was laid by an alternate method of lay where the tubes are not truly parallel, then re-laying would be preferred. If survey control is available, the following is the final step:. Subtract the orienting angle from the azimuth of the orienting line. The difference is the azimuth of the line of fire. Your battalion FDC has instructed you to continue firing from your present position. A survey team is on its way to put you on common survey. In preparation, you place an OS marker directly below the aiming circle plumb bob.
You also establish an EOL at least meters away. Upon closing, the survey team provides you with a grid to your OS and an azimuth to the EOL of 5, mils.
With the howitzers at their lay deflections, you now measure the OA of Leave the platoon laid on , and have the FDC correct its computer entries for azimuth of fire and piece locations. Re-lay the platoon on the originally intended azimuth. If the battery or platoon is to deliver accurate fire, the boresight of the weapon must be correct. Boresighting is the process of ensuring that the optical axis of the weapon sights are parallel to the cannon tube.
The primary methods of boresighting are the distant aiming point, test target, and standard angle. If the sight is off to the right, the tube is disoriented by that amount to the left. If the sight is off to the left, the tube reflects that error to the right.
The angle deflection between aiming point and pantel has not changed from when the weapon was laid. The entire angle has simply rotated by the amount of boresight error. Since the angle has not changed, the deflection recorded to the aiming point is set off on the pantel and the tube is traversed onto the aiming point. The relationship made at the time of lay is now reestablished. It is improper , after correcting for boresight error, to move or fine tune the aiming point to the tube in relation to the deflection numbers originally established at the time of lay.
Emergency occupation of a firing position may require firing before boresight is verified and any error is corrected. In such cases, the howitzers must verify boresight as soon as possible. If this verification discloses an error the line of the pantel and the howitzer tube are not parallel the platoon leader takes corrective actions after measuring the error and reporting it to the FDC.
When a deflection is read from the pantel or when an azimuth is measured, the deflection or azimuth determined is that of the line of the pantel as read from the azimuth counter. If the howitzer is out of boresight, the data derived is inaccurate by the amount of the error.
Note: If the howitzer in question was used to lay the aiming circle or the rest of the howitzers, the other howitzers are out of lay by the amount of error found. The platoon leader should take corrective action to orient them on the correct azimuth of lay after all howitzers have verified foresight. Boresight is verified as discussed below. The numerical error of boresight can be determined from the azimuth counter.
The amount of error is the difference between the required deflection for the alignment device according to the manual and the deflection read on the azimuth counter once the vertical hairline has been aligned. In Btry based operations he will assist the first sergeant. The equivalent USMC billet description is the local security chief. He must be capable to assume the btry gunnery sergeants responsibilities.
Fire Direction Center. The FDC receives data transmitted by target acquisition assets and converts it into data, fire commands, that can be used by the howitzers to engage the target.
Chief of Section. This consists of the cannon sections and ammunition sections. The Cannon section refers to the howitzer itself and the men and the equipment used to engage targets. The Chief of Section is the senior enlisted man located on each weapon. He is responsible for supervising all section personnel on the employment and deployment procedures and considerations of the weapon. This association does not change from position to position. If a howitzer becomes disabled or misoriented enroute to a new location, its associated numbers and all other howitzer numbers do not change.
The computer maintains individual weapon information used to determine an individual weapons ballistical solution. When tactically employed the platoons may be side by side or as much as meters apart according to their mission.
Weapon Formations. It presents an especially easy target for strafing and low level bombing. Command and control when using this formation can become a bit more difficult. Terrain Gun Positioning. This is the primary method used for positioning our howitzers. It is the use of terrain to provide the maximum concealment and protection from the enemy by fitting the howitzers into the rolls, folds, and vegetation of the terrain. All support functions located with the firing element should be positioned to the rear of the howitzers to reduce the amount of activity around the gun line.
This procedure ensures a rapid and orderly movement to and occupation of a new firing position so that you can continue to provide timely and accurate fire support. Hot Sections. These are cannon sections designated by the commander to maintain full crews, at their posts , for instant reaction to fire missions, for a designated period of time. This allows the other sections to perform duties such as PMCS on their equipment, personal hygiene, and anything else to maintain mission capability.
Artillery Carriages. The carriage supports the weapon in the firing and traveling positions. A weapon is classified as either self-propelled or towed depending on the carriage. Recoil Mechanisms. These are designed to absorb the energy of recoil gradually, avoiding violent shock or movement of the carriage. Use the MA1 to discuss the recoil parts. The recoil mechanism performs the following functions:. Breech - The mm howitzers have a sliding wedge breechblock and the mm M series and M howitzers have interrupted screw breechblocks.
M, MA1 have vertical sliding wedges. Firing mechanism. This is a device located on and in the breech of a howitzer. It is used to fire the primer. As the projectile leaves the muzzle the high velocity gases following the projectile strike the baffles of the muzzle brake and are deflected toward the rear and sides.
The gases exert a forward force on the baffles thereby reducing the force of the recoil. This prevents contamination of the fighting compartment by forcing the gases to flow outward through the bore.
This is only found in weapon systems with a turret. The rapidly expanding gases from the burning propellant force the projectile through the cannon tube. Line of Fire LOF. The direction of the line established by the tube or any line parallel to that line in the firing position. It is an imaginary line extending through the central axis of the tube when looking through the breech to the muzzle of the weapon.
An imaginary line extending through the central axis of the tube when looking down through the muzzle to the breech of the weapon. One chart may differ slightly from another because of small differences in construction caused by human limitations in reading the graphical equipment. Because of these differences, the following tolerances between charts are permissible:. All firing unit locations must be checked for accuracy.
For checking the accuracy of two or more charts, plot the same grid intersection on all charts. Determine range and deflection to that grid intersection. If not, all charts must be checked for errors. To ensure accuracy, enough points in the zone of operation of a firing unit should be checked. For example, an error in plotting the unit location on one chart could compensate for an error in constructing the deflection index on the other chart. Checking at least two points will reveal the error.
This should be done as a matter of unit SOP. When survey control and maps are not available, delivery of indirect fires is possible by using observed firing charts.
An observed firing OF chart is a firing chart on which all units and targets are plotted relative to each other from data determined by firing a registration. Observed firing charts are an expedient method that should only be use under emergency conditions and every attempt should be made to construct a surveyed firing chart as soon as possible.
Since all locations are based upon firing data, observed firing charts contain errors because of nonstandard conditions. All observed firing charts are based on a registration. Once a registration is complete, the unit location is polar plotted from the point of registration normally assumed to be a grid intersection by using the direction that is based on the back azimuth to the point and a range corresponding to the adjusted elevation, or more preferably, a range corresponding to the adjusted time.
Because maps and survey are not available, altitudes cannot be accurately determined. When vertical interval and site are assumed to be zero, a false range is introduced into the polar plot range. This inaccuracy can be reduced by trying to determine site. Site may be determined by estimating vertical interval or by conducting an XO's high burst.
Plot this location on the firing chart. The grid coordinates assigned to the point are completely arbitrary. A grid intersection is preferred for simplicity. The grid coordinates of the known point will serve as the basis for establishing a common grid system.
For example, the point could be assigned the grid coordinates of easting E : northing N : , altitude meters. See Chapter All observed firing charts are constructed by using polar plot data. The method for obtaining these data depends on the type of registration conducted and whether site can be estimated or whether it is unknown.
This method is known as percussion plot, VI estimated. The step-by-step procedures for construction of an observed firing chart are listed in Table Determination of Direction for Polar Plotting a. Once the registration has been completed, the azimuth of the line of fire must be determined. No matter what technique percussion or time plot is used, the direction azimuth of the firing unit from the known point is computed in the same manner. There are two methods to determine the azimuth of the line of fire.
They are as follows:. The chart deflection is then converted to an azimuth. For example in Figure , the firing unit was laid on grid azimuth ; common deflection The adjusted deflection was , and the adjusted elevation was Because the firing unit will be polar plotted from the known point, the FDC must convert the azimuth of the line fire to a back azimuth. The polar plot direction is simply the back azimuth of fire to the known point. If the adjusted adj azimuth of fire is less than 3, mils, add 3, mils to it.
If the adjusted azimuth of fire is greater than 3, mils, subtract 3, mils from it. NOTE: When the azimuth of the line of fire is measured, the howitzer is aimed with the adjusted deflection. This will result in a polar plot azimuth that compensates for drift. If the drift corresponding to the adjusted elevation is removed and a chart deflection is determined all nonstandard conditions other than drift affecting the deflection are accounted for in the plot of the known point.
Once the polar plot direction has been computed, the remaining polar plot data must be computed by using one of the methods listed below. Percussion plot is used when an impact registration has been conducted. When VI is not known and cannot be estimated, the method is known as percussion plot, VI unknown. The percussion plot technique assumes that site is zero. The range used to polar plot is the range corresponding to the adjusted elevation.
Since site is zero, the adjusted quadrant elevation is the same as the adjusted elevation. When site is assumed to be zero, a large error can be introduced into the computation of range by using the percussion plot technique. This error can be minimized and the accuracy of the chart improved by estimating a vertical interval between the firing unit and the known point. The firing unit altitude is then determined by applying the estimated VI from the assumed altitude of the known point to the firing unit altitude.
The estimated VI is used to compute site as shown in Table Time Plot, VI Unknown a. The lack of an accurate site and nonstandard conditions are the major sources of error in range on an observed firing chart.
If the site is unknown or incorrect, the derived adjusted elevation is in error by the amount of error in site. Determining the polar plot range from the false elevation produces a false range.
However, the effect of site on fuze settings is usually small. Therefore, the adjusted time can be used as a good indicator of the adjusted elevation and the polar plot range. Because the adjusted fuze setting is a function of elevation and complementary angle of site CAS , the angle of site SI and hence the VI may be determined after the firing of fuze time.
To derive angle of site, subtract the elevation corresponding to the adjusted time plus the CAS from the adjusted quadrant elevation. Determine altitude of the firing unit by applying the VI to the assumed altitude of the known point. This provides an even more accurate relative location. This approximation can be refined to an accuracy approaching survey accuracy by the firing of a modified HB registration after the completion of a precision registration with fuze time.
The vertical interval and site to the known point can be computed by using the angle of site and range corresponding to the adjusted time. The XO's HB registration is fired immediately after the time portion of the registration is completed. The firing of three such high airbursts is specifically what is called XO's HB registration. The height of burst is raised vertically by an amount sufficient to enable the burst to be seen by an aiming circle located within 30 meters of the registering piece.
The burst is raised by increasing quadrant. Three rounds are fired with the adjusted time. The XO measures the angle of site to each burst and determines the average angle of site.
Because the fuze setting was not changed the adjusted time was freed , the elevation plus CAS determined is the true elevation plus CAS. This value is then subtracted from the adjusted QE, yielding a true angle of site. Site is then computed. As shown in Figure , the angle of site to the known point equals got minus - asked for. Setting Up the Observed Firing Chart At the completion of any of the four techniques demonstrated, the HCO will construct an observed firing chart by using the steps in Table A registration was conducted with shell HE, charge 4GB.
The site and firing unit altitude are unknown. Adjusted quadrant elevation: Azimuth of the line of fire reported by the XO or platoon leader: Adjusted deflection: Assumed altitude of the known point: The firing unit altitude equals the known point altitude.
The polar plot range equals the range that corresponds to the adjusted QE. Use the known data from paragraph Determine the first apparent site.
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