Mitch's wife's been kidnapped. They call him to tell him that they want the chopper grounded, so he damages it so it won't fly. Gil and Don who suspect something talks to him and he admits what's happening. So the go to the Captsin and deduce that they wanted the chopper down cause they were suppose to fly aerial cover for a prosecutor who's about to indict several criminals. With info from Mitch, they deduce where they could be holding her and go there. And hopefully they can go back to protect the prosecutor.
When the daughter of a doctor is kidnapped. The kidnappers then call her father to tell him of their demands. And it seems he wants the police to make the ransom drop using a chopper so Don and Gil are told of this. The father only wants her daughter back, so Don makes a suggestion that he parachute out of the chopper after Gil makes the drop. So they do it.