helicopters and downwash

If you have helicopter lifthing a object on a cord of some sort what kind of effects are felt on the object from the rotor while the helicopter is still or moving and what kind of relationship does it have with the length of cord.

 

[jonralph]

Sussest you try the Rotor Craft engineering forum in the aeronautics group, just click on the FORUMS tab at the top of this page.