FM-3-09 Fire Support and Field Artillery Operations Download
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Appendix C C-10 FM 3-09 30 April 2020 Check for increases in pressure. Pressure should decrease smoothly from line to line. Pressure will never increase with height. C-54. Computer MET messages that do not reflect the correct location or current date-time are invalid and do not accurately represent the current weather conditions for the AO. Invalid MET messages should be brought to the attention of the BN FDC for the processing of a new, valid MET message. C-55. The line to line checks reflect basic weather behavior patterns. Regional and topographical characteristics can often produce unusual variances in wind direction and speed. The CMD-P numerical model does not necessarily produce a 100% accurate forecast, but it does not produce non-physical results. The deviations noted do not invalidate the MET message but should be referred to the BN FDC for clarification, especially in cases where the message was transmitted verbally. C-56. In cases where the MET message's validity is called into question, the fire direction officer has a few available options. If this is the first MET message and it cannot be checked against previous MET data, a precision registration should be conducted in order to account for all nonstandard conditions. If a registration is not feasible and line to line errors are in question, the MET may be applied and a check round fired to verify accuracy. If the MET in question is not the first produced by the CMD-P and the FDC has maintained accuracy during fire mission processing with the current MET, a dry-fire verification may be conducted in order to compare firing solutions. With the current met, compute and record firing data (deflection, quadrant elevation, and time fuze setting) for a known point. Next, make the new MET current and compute firing data for the same known point, comparing the two firing solutions. As a general rule, apply the standard tolerances for deflection (±3 mils), quadrant elevation (±3 mils), and time fuze setting (±0.1 seconds). Note: Additional analysis may be needed when firing at maximum ranges, where each mil causes a greater deviation on the ground. Use the appropriate TFT to compare the differences in firing data at the known point target range. C-57. The fire direction officer also maintains the option to discard the new MET and continue firing with the current MET while maintaining accuracy. While made feasible by the ability of the CMD-P to provide a new MET every 30 minutes, the FDC should strive to improve accuracy with every chance afforded. C-58. The passage of time may decrease the accuracy of a MET message because of the changing nature of weather. With existent equipment and technology, the BN FDC has the ability to provide MET messages every 30 minutes. A MET message at this frequency has been shown to dramatically increase the accuracy and lethality of munitions. This however may be impractical and could slow the responsiveness of the firing unit. Generally speaking, a firing unit should request a new MET message every 2 to 4 hours, depending on the tactical situation. C-59. It is critical for a firing unit to request and receive a MET message when: Upon entering the initial firing position. Any movements more than 4 kilometers, but the target area remains the same. Anytime direction of fire is more than 800 mils from the original target location. Anytime there is a significant change in weather; that is, a storm front comes through or the temperature increases or decreases. During transition periods. MANUAL COMPUTATION OF MET C-60. For manual MET procedures use DA Form 4200 as outlined in TC 3-09.81.