Rotor downwash can be a serious problem for pilots of light fixed wing aircraft. I've been bounced on the ground in a light twin by an A109 which lifted from the fuel pumps 30 metres away and banked to the right, blasting me with downwash before climbing out and I've been "flicked" sideways on short final when an errant pilot took off in a Twin Squirrel across my path (I took control from my student and executed a Go Around, he had an engine failure and executed a "run-on landing" - or whatever you call it - interesting one that!). Even the lightest of helicopters can catch you out if you're downwind of them within 30 metres or so. There does seem to be a lack of awareness amongst ATCOs/FISOs and the area around the fuel pumps is the most dangerous. I've heard of a microlight pilot sustaining hand/arm injuries whilst holding onto his machine as a heli passed by, and the story of an S61 lifting an Islander as it air-taxied past. When parking the aircraft, I advise my students to put in the control locks at all times, even if the wind is flat calm, just in case a heli passes by.