in White House Down, We see in the following youtube clip:
That when special forces went to attack the White House, the captives fire a javelin missile at the helicopter and it crashes.
The second one hits the ground when hit by a missile and crashes into the pool (it catches fire)
The third one: Manages to deploy a few troops by fast roping onto the the White House roof, but is blown up by an incoming missile and crashes into the White house itself.
After all this the troops are still inside the helicopters.
How did they film the helicopter crashes while the troops are still in them?