The Acceptable Margin of Error

by Sergeant First Class Thomas J. Lindsley and Captain Lloyd A. Davis "Calibration vs Zeroing," in the September-October issue of ARMOR, was a good attempt to address a very sensitive topic, but we would like to add some additional comments. We have some concerns about tank gun accuracy and want to shed some light on areas that are of major concern to any armor professional interested in accurately putting steel on target with a high first-round hit probability. The bottom line is that we should examine how to exploit the system advantages of the MlAl tank. We can obtain proof of this need by observing what is done on many screening ranges, or by listening to conversations behind the closed doors of many units that seriously consider individual zeros in the event of imminent combat. One method of improving first-round hit probability would be to increase the range to the screening target and decrease the size of the target. Another would be to construct a "Hit Zone" on the current target at the current range. In either case, not meeting the standard would justify conducting a proofing test, a thorough check of the fire control system to eliminate faults. The increased expenditure of ammunition for proofing could possibly be recouped through an increase in first-round hit percentages. Thoughts from the Field There are well-understood limitations in our current procedures to confirm tank gun accuracy. The "Fleet Zero Policy" has considerable merit from the standpoint of conserving ammunition. But you do not get individual zeros nor compensate for the error expected from various lots of ammunition.

Few tankers will disagree with the fact that fleet zero works well for the majority of gun systems. But whenever results are an average (a fleet zero is basically that), a percentage of those results will deviate from the norm. In this case, a small group of tanks will deviate from the acceptable norm. Most vehicles will screen rather closely to the target center, while others will hit somewhere near the edges of the panel. This performance will generally repeat on other firing occasions, the most important of which will be combat.

What is Really Happening Out There?

Figure 1 represents a tank ba talion's performance during calibration screening at New Equipment Training in Grafenwoehr, Germany. At first glance, it is apparent that this entire battalion successfully passed on its first attempt. This can lull crews into a false sense of security, and make them feel they have a high degree of first-round hit probability. For most crews, this sense of security is justified. Figure 2 approximates what would happen to the same shots if the screening range were increased from '1,200 to 2,100 meters. A considerable number of crews would miss the 2,100 meter target, and many of those who did hit would not likely achieve a kill. Figure 3 represents the probable effects of firing at a T-72 in a hull-down position. (Remember that crews that fired in Figure 1 were not under the stress they will encounter in combat). The outcome is even more significant when engaging a BMP because it is a smaller target. The target distances used for Table VI11 are barely within the error accepted in the fleet zero policy. It is the GO TO WAR experience that will tell much about the full impact of this procedure (Figures 2 and 3).

A considerable number of units are using methods other than calibration-by-screening to accurize weapons systems. One popular technique is to apply the published flect zero data as a start point for screening, and then use some tighter standards for accuracy. For example, a circle one meter in diameter is drawn around the aimpoint on a standard screening panel. If the round impacts outside of this circle, the unit will employ one of two steps beyond this. Some will relay on target center, depress the ZERO key on the computer control panel (CCP) and remove apparent error by toggling to the strike of the round. Others may fire a second or third round, then use the CCP and toggle to the mean point of impact. In either case, the new data is recorded and used in place of the fleet zero data for that tank. Why Not Individually Zero? A major argument for using the fleet zero policy is the prohibition against firing depleted uranium ammunition in peacetime, thus 18 ARMOR -

_ _ eliminating the ability to individually zero combat ammunition. Furthermore, one cannot expect an in- dividual zero for training ammunition to be effective for service am- munition. Another reason is the anticipated occasion-to-occasion devia- tion expected when firing different ammunition from different lot numbers. The reality is that a fleet zero for service ammo will still be an "average," and there will be a percentage of tanks that will not be able to hit with a reasonable hit probability at extended ranges. Would you want it to beyour tank? One can justify further investigation into this matter by those who desire to get more bang for the buck. Address your concerns to the Armor School. We understand that this is a very complex issue involving great amounts of money for research and ammunition develop- ment. Bul if you have any doubt about potential payoffs, look again at Figures 2 and 3. SFC Thomas J. Lindsley has served as troop master gunner, C Troop, 1-10th Cav, and platoon sergeant and battalion master gunner, 3-66th Armor, at Fort Hood. He is currently assigned as master gunner, Headquarters, USAREUR in Grafenwoehr, FRG. Captain Uoyd A. Davis received his ROTC commission in 1981 from Morgan State Universlty, Maryland. He has served as platoon leader, H Company, 2-6th Cav at Fort Knox, Ky. and platoon leader, C Company, 3-73rd Armor, at Fort Bragg, NC. He is currently the Commander, HHT, 1-1 1 th ACR. ARMOR - July-AuQuSt 198; Fig. 1 Fig. 2 Fig. 3 MSPERStON PATTERN

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