Mortar Firing Direction Procedures

METEOROLOGICAL MESSAGE

MET messages provide information about air temperature and density, and the speed and direction of the wind between the mortar and the targets. The validity of a MET message decreases over time. There are no specific rules for determining how long a MET message is usable, since that determination depends on the atmospheric conditions. However, four hours is considered the maximum usable duration for a MET message.

Lay of the Section

When all mortars in the section are mounted and using Mortar Fire Control Systems, they use terrain positioning. When operating in degraded mode or as required for training, the section leader lays the section parallel on the prescribed azimuth with an aiming circle. The mortar section normally fires a parallel sheaf. To obtain this sheaf, the mortars must be laid parallel. When a section moves into a firing position, the FDC determines the azimuth on which the section is to be laid and notifies the platoon sergeant (or section leader). Before laying the mortars parallel, the section leader calibrates the mortar sights. All mortars then are laid parallel using the aiming circle, mortar sight, or compass. The section normally is laid parallel by using the following steps:

FIST

Fire Support Team

FSE

Fire Support Element

Charge

Charge is defined as a propellant. Mortar propellants are low-order energetics that burn rather than detonate. Propellant is the mortar fire's semi-fixed ammunition. When gases from the burning propellant develop enough pressure to overcome projectile weight and initial bore resistance, the projectile begins to move. Gas pressure peaks quickly and subsides gradually after the projectile begins to move. The peak pressure, together with the travel of the projectile in the bore, determines the speed at which the projectile leaves the barrel. Factors that affect the velocity of a mortar-ammunition combination include the

What makes up Indirect Fire Team?

FIST FO FDC Gun Line

FDC

Fire Direction Control

LHMBC

Lightweight Handheld Mortar Ballistic Computer The LHMBC can calculate solutions for all existing U.S. mortar ammunition across all weapon calibers, and can be readily upgraded as new rounds become available. The LHMBC incorporates all functions essential to directing safe and accurate mortar fire including MET compensation, registration, smoke card, Fire Support Coordination Measures, Safety Fan, and plotting. Mission capabilities include, but are not limited to: Grid, Shift, Polar, Search, Traverse, Final Protective Fires, Quick Smoke, Immediate Smoke, Coordinated Illumination, Immediate Suppression, Direct-Lay, and Hip-Shoot.

Reciprocal Lay

Reciprocal lay is a procedure by which the 0 to 3200 line of one instrument (aiming circle) and the 0 to 3200 line of another instrument (sightunit) are laid parallel. (See figure 1-3.) When the 0 to 3200 lines of an aiming circle and the 0 to 3200 line of the sightunit are parallel, the barrel is parallel to both 0 to 3200 lines, if the sight has been calibrated and boresighted properly. The principle of reciprocal lay is based on the geometric theorem that states if two parallel lines are cut by a transversal, the alternate interior angles are equal. The parallel lines are the 0 to 3200 lines of the instruments, and the transversal is the line of sight between the two instruments. The alternate interior angles are the equal deflections placed on the instruments.

TFT

Tabular Firing Table Firing tables are based on firing the weapon and its ammunition under, or correlated to, standard conditions.Those standards are used to compensate for variations in the weapon, weather, and ammunition at a given time and place. The atmospheric standards in United States firing tables reflect the mean annual conditions in the North Temperate Zone. The main elements measured in experimental firing are angle of elevation, angle of departure, muzzle velocity, attained range, and concurrent atmospheric conditions.

M16 Plotting Board

The M16 plotting board consists of a base, azimuth disk, and a range arm or range scale arm

Azimuth Disk of M16

The azimuth disk, made of clear plastic, is roughened on one side so that it can be written on with a soft lead pencil. The azimuth scale on the outer edge is numbered every 100 mils (from 0 to 6300) and divided every 10 mils with a longer line at every 50 mils, giving a complete circle of 6400 mils.

Base of M16

The base is a white plastic sheet, bonded to a magnesium alloy backing. The grid system printed on the base is to a scale of 1:12,500, making each square 50 meters by 50 meters and each large square 500 meters by 500 meters. At the center of the base is the pivot point to which the azimuth disk is attached. Extending up and down from the pivot point is the vertical centerline. The vertical centerline range scale is graduated every 50 meters, and numbered every 100 meters from 0 (pivot point) to 3,100 meters, with a total range from the pivot point of 3,200 meters. The vertical centerline ends with an arrowhead at the top of the board. (1) The arrowhead, known as the index mark pointer, is used in determining azimuths and deflections to the nearest 10 mils. It points to the index mark of the vernier scale (0 mark), which is used to determine azimuths and deflections to the nearest mil. The vernier scale is divided every mil and numbered every 5 mils, with a total of 10 mils left and right of the 0. (2) The secondary range scale, to the left of the vertical centerline, is numbered every 500 meters (from 0 to 6,000) with a total range of 6,400 meters. It is used to determine range when the mortar position is plotted at points other than the pivot point. Two additional range scales, 1:50,000 and 1:25,000, are on the right-hand edge of the base. They are used with maps in determining ranges.

Range Arm of M16

The range arm, made of plastic, is used when the mortars are plotted at the pivot point. The arm has a vertical centerline with a range scale and a vernier scale, both of which are the same as on the base.