blunt force is what happens when you smash into something. You can sever the arteries in your heart and die from a car crash impact without any other signs of damage to your body, simply because your skeletal system stops moving suddenly, but your organs are still carrying that inertia.
Them dying from blunt force is what happened when teh helicopter smashed into the ground. Death would have been instant. Burns and smoke and all that is what happened to the dead bodies after blunt force death.