Rotor wash you might encounter from a helicopter hovering or hover taxiing is rather different than a helicopter in cruise flight. When you are in flight, avoid the helicopter as you would an airplane of the same size (don't follow it - wake turbulence). A cruise flight helicopter makes a wake similar to a plane.
If the helicopter has lifted off a runway, treat all the air from the lift off point onward (and considering the turbulent air being blown by the wind) as the lift off point of a heavy jet. You would not land in, nor fly through air in the area of rotation of a heavy jet on takeoff, so don't fly through the helicopter's wake either.
Yes, planes have crashed, because the pilot tried to fly through (even just an overshoot) the helicopter's wake, and it did not work. Think about it, if a 20,000 pound helicopter is hovering, 20,000 pounds of air is on the move around it at every moment - how much of that 20,000 pounds of air can your plane get tangled into? How much does your plane weigh?
If you are taxiing, Give it at least five rotor diameters away from the helicopter in all directions. If in doubt. stop and wait. If he flies near you, his wake is his responsibility. When I hover taxi, I give taxiing planes the widest birth I can manage - as I am usually not bound by taxiways.