Hmm... Well, I'd start by maybe placing an HV emitter around the ground area that you're wanting to have the dust emerge on.
Tie the birth rate of particles to the distance to the chopper object (so you get more dust as the thing approaches the ground), and adjust the motion properties so that the initial motion is upwards only. Don't set any collision properties for the various objects in the scene so your dust HVs will simply pass straight through stuff rather than bouncing around, should give you a reasonably natural look.
Or, if your camera is static, why not try to fake it with animated transparency on a series of image planes? Gotta be quicker to render ...
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