crab,
Yes. It is assumed that the temperature is a constant.
The idea in my last post was an alternative to the concept that there is a higher pressure below the blades pushing upwards. What might be considered as the 'air cushion'.
Perhaps the ground increases the air pressure (density) in whole area in which the rotor is working. I.e. above, below and to the sides of the rotor. The rotor therefor performs as if it was operating at a much lower elevation then it actually is. In other words, better thrust for the same power.
Dave J.
Oops!! ~ Edited to apologize and correct above error.
The thrust of the rotor does not vary with altitude. It is the power of a naturally aspirated reciprocating engine that varies with altitude.
Last edited by Dave Jackson; 4th Dec 2002 at 20:50.