What a super weapon! I wonder if the helicopter was landed or hovering(NAP)? Maybe, just for the sake of your scenario, you can clear the weapons to 0. Or, turn off the weapons. But then, having an armed indestructible Hind sounds like it spiced up the game a bit.
If you play the 7th battle of the 3rd campaign you will have the chance to fight inside an airfield.
All the grounded helos must have their weapons deleted (modify key D).