Another approach. Again with a locator at the helicopter and parented null underneath the surface of geometry. (I have not been able to find a way to set up an "aiming" point which will use the rotation from the helicopter to control a point on the surface.) With those two points in place constraining in XZ a NURB circle (curve) which has been projected on the surface of the object. This projected curve can be used to emit particles which, once assigned a "per-vertex" radial force, will affect the hair system.
Theoretical approach. One which I did not take the time to flesh out, but is involving just particles emitted from the helicopter (potentially the best possible solution.) With a nice lifespan indicative of the force generated by rotors. Setting up an interaction that when the [directional emission] contacts the surface, new particles are produced which effect the hair system. (most likely with a per-vertex radial field).
A rough video of my work is coming this afternoon. (I've been rendering all night and getting weird warnings which I need to look into fixing.)