What do you mean by "departure of a heli in down wind" ?
Syntax/lost-in-translation issues aside, and assuming you're referring to helicopter operations within the United States, it sounds like the answer to your question can be found somewhere in section 3-11-2 ("Helicopter Takeoff Clearance") of the FAA's 7110.65V. Perhaps especially relevant might be 3-11-2(c):
c. Unless agreed to by the pilot, do not issue downwind takeoffs if the tailwind exceeds 5 knots.
A pilot request to takeoff from a given point in a given direction constitutes agreement.