Originally Posted by richard hanson
- I think you made a bit of a leap on the comparison.
Trying to hover next to a ceiling would be very difficult ! Trying to hover right next to the ground is also problematic
Ideally the rotor does not have to deal with air flow except for air which comes from directly above
Everyone who has actually tried this - what do you think?
I have to agree with Richard here. Hovering near the ground is difficult for the exact same reason hovering near the ceiling is difficult - thrust changes as a function of altitude. That doesn't mean the aerodynamic phenomena causing the stability issues are the same, though.
EDIT: Actually, I have to make one more note here. ShoeDLG is right in that near the ground the effect is statically stabilizing, whereas near the ceiling it is destabilizing. However, near the ground you still run into dynamic stability issues because there is relatively little damping of those vertical oscillations in hover.