Let's not forget the effect of rotor downwash on bystanders (or pax) too. First time I ever went on a Chinook we boarded via the rear ramp with the rotors turning. I was carrying a Bergan (as we all were). The "sail effect" provided by the Bergan, once I got under the rotor disc, nearly took me off my feet.
There's a lesson there, but I'll leave it to others to tease it out.
P