D3, i will read up on impulse theory and blade element theory - you are right i am a little rusty. Agreed that the downwash velocity will be lower with ground effect. The suprise for me is that the stagnation pressure ends up higher than in the free stream.
At some point i intend to study CFD, and this strikes me as an interesting project. It's clear to me that aerodynamics is more complicated than can be easilly captured in a simple calc. The fact that tall grass consumes hover power, although you feel it should help, is an indication that even this is more complex than it first appears...
Last edited by Graviman; 3rd Dec 2007 at 18:13.