How to apply corrections when firing illumination shells

During night combat operations, artillery units perform not only fire missions aimed at destroying targets but also:

• Illuminating terrain and targets;
• Setting light markers;
• Blinding enemy observation posts, command points, and firing systems.

Contents:

• How an illumination shell works;
• Optimal height for flare burn;
• How to apply corrections.

How an Illumination Shell Works

At a distance corresponding to the time fuze setting, the fire stream from the fuze ignites the expelling charge. The gases from the expelling charge press against the diaphragm, which pushes the cup cover, and the cup against the cylinders, causing the base of the shell to shear off. Simultaneously, the fire stream from the expelling charge ignites the illuminant element. After the parachute and illumination element are ejected from the shell body, the half-cylinders fall away, the parachute opens, and the illumination element attached to the parachute slowly descends, lighting up the area.

Optimal Height for Flare Burn

The standard burst height of an illumination shell is 400 meters at all ranges and charges for 122 mm and 152 mm howitzers, and 600 meters for 155 mm howitzers. One illumination element produces light ranging from 400,000 candles (122 mm, 155 mm) to 800,000 candles (LU 216 ILLUM IR shell) and illuminates an area in a circle with a diameter of 1,000 to 2,400 meters (LU 216 ILLUM shell). Illumination lasts from 50-55 seconds up to 80 seconds with modern NATO shells. The flare descent speed is about 7 m/s.

How to Apply Corrections

The optimal height for flare burnout is 50 meters above the surface. To adjust the flare’s burnout height:

• For illumination shells, corrections are applied via the level setting;
• For illumination mines, corrections are applied by adjusting the fuze.

If the flare burns out on the ground:

• Use a stopwatch to determine the flare’s burnout time, multiply it by 10 (for illumination shells);

• Add 50 meters to the result to get the correction for height in meters:

  hₓ = tₓ * 10 + 50 m

• Convert the correction into level increments. Increase the level setting accordingly.

  ΔR = hₓ / 0.001Dₓ/t

Where:

• tₓ — flare burn time;
• hₓ — height correction in meters;
• ΔR — level correction in mils;
• Dₓ/t — range to the target (in meters).

Example of Level Correction Calculation:

• Topographical range to target: Dₓ/t = 6600 m
• Flare burn time on the ground: tₓ = 1.5 sec

hₓ = 1.5 * 10 + 50 = 65 m (the flare needs to be raised by 65 meters)
ΔR = 65 / (0.001 * 6600) = 0-10 mils (increase the level setting by this amount).

If the flare burns out above 50 meters:

To calculate this, the angle of the flare’s burnout position is required. However, considering that modern warfare against Russian forces often involves drone-assisted corrections, the drone operator may not be able to provide the angle relative to the horizon. The operator should intuitively estimate the time it takes for the already extinguished flare to fall, knowing the descent speed is 7 m/s. Then, subtract 7 seconds (the time for the flare to fall the last 50 meters) and use the earlier formula with the opposite sign (the level setting will need to be decreased).