Chapter 14
EMERGENCY FDC PROCEDURES
Field artillery units must be capable of delivering fire at all times. Requests for immediate fires may be received when the unit is moving or when the FDC is not yet set up. The loss of personnel or equipment may cause the battery to rely on some type of emergency backup procedures. The firing battery executing an emergency fire mission has two priority technical fire direction tasks:
- Determine initial firing data to the target.
- Prepare for determination of subsequent data on the basis of the observer's corrections.
14-1. Methods of Determining Initial Data
The first priority is to compute initial data, announce it to the piece, and fire a round. Depending on the call for fire, the XO or FDC may accomplish this by using one of several methods:
a. Adjust Fire. The platoon leader determines direction and range to the target grid location from the map-spotted platoon location. This is done most rapidly by using a map and a range-azimuth fan of the correct scale (Figure 14-1). The platoon leader directs that the platoon be laid on the azimuth to the target, or he may orient the base piece himself by using the howitzer backlay method or a distant aiming point. If he has time, the platoon leader should lay the base piece with an aiming circle. The platoon leader selects a charge, or uses the standard charge, and converts the range to an elevation. The initial firing data are announced to the piece(s).
(1) Deflection equals the common deflection for the weapon system in use.
(2) QE equals elevation corresponding to range to target (GFT, TFT, and so on). Site is ignored unless it is excessively large. The FDO or platoon leader is responsible for analyzing the terrain in the target area and checking intervening crests to determine if he should include site.
b. Mark Center of Sector. This is requested when the observer is not oriented to the terrain. The platoon leader determines direction and range to the center of the supported unit's zone of action from the map-spotted battery location. If the platoon leader is not sure of the situation or the location of the sector center or if he feels a center of sector round may be unsafe, a white phosphorus with fuze time for an airburst should be fired. The platoon leader directs that the platoon be laid on the azimuth he determines to the sector center. The platoon leader determines the elevation corresponding to the range and charge. The initial firing data are announced to the piece.
(1) For a WP or an HE high airburst, the trajectory is raised to a 200-meter HOB by using the100/R factor. The FS corresponding to the initial elevation is used. The error introduced by a vertical interval greater than 100 meters is ignored.
(2) If shell HC smoke or WP is requested, HE data are fired without making corrections for projectile weight. For shell HC smoke, the time fuze setting to fire is determined by subtracting 2 seconds from the FS corresponding to the HE elevation.
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NOTE: A grid location is preferred over mark center of sector because the first round fired engages the target directly. |
14-2. Methods of Determining Subsequent Data
After the initial fire commands are announced, emergency equipment must be prepared to convert the observer's corrections into subsequent fire commands. There are several expedient means of obtaining subsequent data that are available to the XO. He or the FDO must be able to quickly convert observer corrections into firing data.
a. Emergency Firing Chart. Use of the emergency firing chart to adjust fire is discussed in paragraph 14-3.
b. M10 or M17 Plotting Board. Use of the M10 or M17 plotting board to adjust fire is discussed in paragraph 14-4.
c. Black Magic. If no other means of adjusting fire is available, the Black Magic technique may be used as a last resort. Certain information must be available, as detailed in paragraph 14-5.
14-3. Emergency Firing Chart
a. The emergency firing chart employs the same basic techniques as observed firing charts. Establish location and direction by using the relationship between the firing unit and its targets. The relationship is determined by firing and will contain errors. The emergency chart is only a temporary expedient to be used until a surveyed chart can be constructed.
b. The emergency chart may be constructed on any surface suitable for plotting (can accommodate an RDP and plotting pins).
c. Use Table 14-1 to construct an emergency firing chart.
14-4. M10 or M17 PLOTTING BOARD
a. The M10 or M17 plotting board may be used for determining data for subsequent corrections in place of an emergency firing chart. Once prepared, observer corrections along the OT line can be converted to corrections along the GT line. For this procedure, the rivet (center) of the plotting board represents the location of the last burst.
b. Use Table 14-2 to determine data for subsequent corrections in place of an emergency firing chart.
14-5. Black Magic
a. Black magic can be used to determine both initial firing data and firing data that are based on subsequent corrections. This technique can be done by FDC personnel or the observer and should only be used as a last resort.
b. Table 14-3 gives the steps for the Black Magic procedure.
c. Subsequent corrections are processed by using the steps in Table 14-4.
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NOTE: Subsequent corrections are made with respect to the GT line. |
14-6. Emergency Firing Chart Example
a. You receive a call for fire while traveling to your next position. From a map spot, you determine the range to the target to be 4200 and the direction to be 4950.
b. Use Table 14-6 to process the mission.
14-7. Black Magic Example
a. You receive a call for fire against a platoon of infantry in a trench line. You estimate the range to be 3,400 meters and the direction of fire to be 4750. The observer requests time in effect.
b. Use Table 14-7 to process the mission.
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