1. Spawn a Blackfoot chopper or Mi-48 and a playable soldier. Spawn some enemy vehicles and choppers somewhere.
2. Enter the chopper as a pilot and fly to the enemy locations, enable Manual fire, switch to your DAGR missiles(if in the blackfoot) or the AG missiles that the Mi-48 has, try to lock onto the targets by right clicking or pressing the tab key, but you'll see that nothing happens)

If you have a blackfoot, you can switch to the ASRAAM Air to air missiles and you wont be able to lock onto the enemy choppers.
If you have a rotary cannon, you wont be able to lock onto anything and wont have the marker on the box that shows when to shoot.

If you repeat those steps but with an AI gunner with you, you'll see that you can lock onto the various targets fine.