Helicopter blades- incorrect motion blur- Huh?

[lou4uandme2]

Hi,

I need to render a helicopter flying forward. I rendered out a velocity pass to use in Nuke.

I had horrible results when I made the blades spin 10 rotations per second   So, I slowed down the blades and got the results below. Not great, but I would live with it. The test was with the helicopter sitting still.

But when I put the helicopter in motion (flying)  I got horrible results. I also separated the blades in a render  layer

but I can not get the desired typical look of the blades.

Any help would be greatly appreciated,

Thanks!<bottom> 

Pasteboard - Uploaded Image

[mcw0]

More info would be helpful.  Which renderer are you using?  Is there substep control for motion blur?