P6-113 Fire Support: Calculations

Calculating your fire elements

When fire mission figures (grid) or a landmark has been given you need to do some map work:

• Mark the target grid or landmark on your map and note down its elevation

• Grab your map tools while you are on the map (Ace self interact) and put the dot in the middle on your exact position and note down your elevation.

• Turn the map tools (ALT), so the red arrow is going directly through your target

• Read off the number from the outer circle, note it down 

• Move your map tools (right click and hold), so that the zero of the long side is exactly on your fire position

• Read of the range on the ruler and note it down. The range needs to be noted down in meters

Technical side-note: If you have a hard time reading your map tools, or you are not seeing the dot in the middle, increase your texture quality settings.

Once you have finished the previous step you should have noted down

• The elevation of your position

• The elevation of your target

• The direction in mils from the fire position to the target

• The distance from you to the target

Range Tables

You can open your range table via the Ace self interaction menu under equipment.  

On the left of the range table you can choose your charge. In the picture: "Charge 0" "Charge 1" and "Charge 2".
The charge is responsible to propel the shell out of the mortar’s cannon. 

Additionally, you will find the following information:

• Range this is the range the round can fly with the current charge

• Elevation is the the elevation needed to go that distance

• D ELEV per 100m DR is how much the elevation needs to drop per 100m height difference. 

  • This means that if the Mortar is at an altitude of 120m and the target is at 20m respectively. This figure needs to be added to the ELEV from the second column. Remember: Mortars are higher angle group.

• Time of flight DR is amount the flight time will increase or decrease depending or the height difference

• Time of flight is the amount of time the round needs to fly to hit the target

Interpolation

What if the range you want to shot at is between two ranges shown on the range table? You have to do some interpolation. That sounds like a fancy word, but is very easy to do here is how:

Consider this extract of the range table for charge 0:

Consider the following example: You want to hit a target at 425m which is exactly at an altitude 50m below you.

For the range:

1. 425m is exactly halfway between 400m and 450m.

2. The difference between the ELEV is 1127 - 1029 = 98 Half of this is 49. So you take your ELEV at 400m minus 49, which is 1127 - 49 = 1078

For the Altitude

3. The absolute difference between the D ELEV is 61- 91 = 30. Half of that is  15.

4. As the fire position in higher than the target and we are firing in the higher angle group you must add that to your ELEV: 1078 + 15 = 1093.

5. Set your mortars ELEV to 1093. And write down Time of flight

Note: You will use the Time of flight in order to time when you need to tell your Forward Observer that the first round is going to impact by saying “SPLASH” over the radio approximately 5-10 seconds before impact.