Before asking the question you need to know why is the helicopter crashing? Did the engine fail? If that is the sole reason, there is a chance that you will survive.
In the case of the engine failure, if the main rotor is turning freely, a technique called autorotation is used. For a person to become a licensed pilot, it is necessary to learn how to autorotate a helicopter. As soon as the engine dies, pilot lowers the collective. The collective determines the angle of attack of rotor blades. Lowering the collective spins the rotor while the altitude drops which results in the reduction of the rate at which the rotor is slowing down.
If you are in a larger chopper, there is a good chance that it has a twin turbine engine. Failure of both the engines is quite a rare event. Check out the video of a helicopter landing without engine power.