A helicopter crash is maybe one of the coolest things to watch ever. Helicopters don't just blow up. First they usually suffer some kind of malfunction that sends them spiralling through the air. Then when they hit the ground the rotors get all busted and the helicoter skids (sometimes bounces) along the ground before hitting something, then blowing up.
A helicopter is probably on of the must unreliable aircrafts ever since it's so vunerable. One shot from an RPG and you can kiss it good bye. Those rotors get tangled up to something and that helicopter won't be flying for much longer. The only positive thing is that you may have a better chance to survive a helicopter crash than a plane crash.