Its in the huge PDF manual, found in your installation folder.
however I could not find where the manual mentions anything about target armor arc command, dunno if it has been updated to reflect this after the recent ai patches.
edit: It is not in the normandy manual but it was in the blitzkrieg manual
(although normandy now supports this now)
"An alternative to Target Arc is Target Armor Arc. It functions the same as Target Arc, except
that a unit with this command will only engage enemy armored vehicles within its arc, and
will leave soft targets like infantry alone. This is useful if you do not want your anti-tank
weapons to reveal themselves too soon against enemy scouts."
"Any visible enemy units that are located inside this area, or that move into this
area, will be fired upon. Any enemy units outside of this target arc will be
ignored (until self-preservation takes over and the Tactical AI decides to
override player orders; e.g. if an enemy unit suddenly pops up at extremely
"is also useful to keep a unit’s “attention” focused on a specific
part of the game map while it moves. If, for example, you want to keep a
close eye on a bunch of buildings (where you suspect enemy activity) while
driving down a road, you could assign a target arc to several units covering
this area. The target arc increases the chances that units will recognize and
engage an enemy threat within the target area quickly"
setting a target arc with vehicles make it so the acquisition time is less, so the tank, rifle or mg doesn't have to swing its barrel around to shoot, the barrel is already pointed at the center of the target arc you set. So yes it makes it so it can shoot faster.
That is where self-preservation takes over and the Tactical AI decides to
override player orders takes place.
I never use any of the target arcs but manage out just fine staying hull down or hidden with opening up and closing the hatch in a quick pattern to see targets. I know there are great benefits to it that I am missing, but the AI and skill of the soldier do a pretty good job now.