It is a while since I operated from Aberdeen but ATC were very careful. A couple of incidents of light aircraft being blown over by taxiing heavy twins and some close calls make them much more aware than most ATC.
I recently flew into the wake of an S-92 in a very light aircraft - he was in the cruise doing about 120kts and light - it was a flight test, he went right and cut across my course and I did not climb fast enough. The turbulence was pretty intense although quite localised.
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I would guess as the speed drops off the area of turbulence increases. Either way there is something about the turbulence from choppers than seems to make them pretty difficult for light aircraft. On a calm day 5 minutes plus seeems sensible. If you see an S-92 and are likely to cross its wake climb!