Hi Chocks,
The R22 rotor is approx 25ft dia so X 3 would be about 75ft, but the wash from a Robbie wouldn't ruffle any feathers at that distance, also the wind would have to be blowing at about 18/plus Knts to even start to push the robbie into your way, as you have not flown R22 they always weathercock into wind, and if being flown by a low time Student would not be out in anything greater than 8/10 KntAbs max wind unless with a FI or CFI, normally also when on your approach to the field did the ATC not warn you of Heli movements, if they did when you acknowledged that they would then tell the Heli of your imminent aproach/depart which they(the heli) would then have to acknowledge, from my past experience on a mixed training field mixed with commercial departures and landings the Heli would either Hover and wait for your move to start/finish or would land and wait with Rotors running, no big problem either way as long as you are all aware of each other.
My Regards
