Well, the visual signal stuff was not developped and trained for the time when the radios are not functioning. Those procedures have been developped for combat operations in comm-out conditions.
It is possible to conduct a complete 4-ship low-level mission without doing one single radio call. We trained it, did it and it worked. There are signals for a variety of situations, with the whole aircraft, with hand or head signals, and finally close in with the grease pencil.
Comms can be jammed, can be listened at, can be jiggled with and they give away your position and finally your intention.
franzl