## 6 Determining the Likely Range of Vertical Impact Angles
### Consequences for the Considered Cage Armour Systems  
#### 6.3.1 Ballistic Efficiency Comparison  
The maximum impact angle of approximately 11\({}^{\circ}\) has as a practical consequence that for an RPG-7 shooter located at the same altitude as his/her intended target, the projectile will normally impact at an angle below 11\({}^{\circ}\). The direct consequence for a cage armour system is then that it will normally be hit by a projectile at an angle below 11\({}^{\circ}\) in the vertical plane. Although the assumption of the shooter being at the same altitude as the target may seem fairly restrictive, this is actually not the case. Firstly, actual altitude differences between a shooter and the target tend to be relatively small, even in mountainous areas, due to the fairly limited accuracy of the RPG-7 weapon system. Due to this, most tactical firings tend to be at less than 500 m. Secondly, if there nevertheless is an important altitude difference between the target and the shooter, the roof section of the vehicle will rapidly  
Figure 28: Impact angle as a function of horizontal flight distance (range). Figure 27: PG-7 projectile trajectory as a function of launch angle. Trajectory segments above the initial altitude of the weapon system are marked in green, trajectory segments below are marked in red. The trajectory corresponding to the maximum horizontal flight distance is marked in blue (9\({}^{\circ}\) launch angle). The maximum flight distance due to the 5 s delay of the self-destruction function is also indicated (orange line). present by far the largest projected area of the vehicle. As the roof section is normally not protected by the cage armour system, these large impact angles will only very seldom lead to impacts on the cage armour system. The results of Section 5.2.2 can then be reassessed taking this maximum impact angle into account. Although no significant yaw angle components were observed in the vertical plane during all experimental campaigns, the results were reassessed, assuming a maximum vertical impact angle of 15\({}^{\circ}\). This also takes into account the possible inaccuracy of the used PG-7 trajectory model. Assuming then a uniform distribution for the horizontal impact angles of 0\({}^{\circ}\) to 90\({}^{\circ}\), and from 0\({}^{\circ}\) to 15\({}^{\circ}\) for the vertical impact angle, average efficiency of each considered cage armour system can be calculated. The results for the different considered cage armour systems are given in Figure 29. The limitation in maximum vertical impact angle largely negates the perceived drawback of the slat and bar armour systems, namely their reduced performance with increasing vertical impact angle. The more complex net systems show a significantly lower average efficiency due to their susceptibility to the horizontal impact angle and the relatively lower performance for close to horizontal impacts. The inertial distributed weight cage armour does not show a large increase in performance compared to the other systems, despite its relative complexity. However, just as for the aforementioned decrease in the likelihood of impacting the vehicle sides with increasing vertical impact angle, the likelihood of impacting with a large horizontal impact angle decreases rapidly for horizontal impact angles above 60\({}^{\circ}\) due to rapidly diminishing corresponding projected area. Next to this, the standoff distance and projected armour thickness (seen by the jet) will also increase considerably, reducing the probability of a complete perforation and casualties on board the vehicle. Figure 29 hence also shows the average efficiency of the different considered cage armour systems assuming a uniform distribution for the horizontal impact angles of 0\({}^{\circ}\) to 60\({}^{\circ}\) instead of 0\({}^{\circ}\) to 90\({}^{\circ}\). A uniform distribution is again presumed for the vertical impact angle from 0\({}^{\circ}\) to 15\({}^{\circ}\).