On Thu, 27 May 2004 at 18:20:14 in message
.net, Mike Rapoport
wrote:

The airplane efficiency is related to altitude. It takes a lot less thrust
to move an airplane at any given TAS at 30K' where the are is only 30% as
dense than at sea level.

Help me here. I am struggling to find out more information but I have a
bit of a problem with that statement. I probably misunderstand what you
are saying and I may have it wrong I admit. In essence it is correct but
you normally fly at much higher TAS at altitude than at sea level.

It seems to me that if you want range you fly the aircraft at the AoA
that provides the best overall lift/drag ratio.

Let us suppose that is a ratio of 10. Then at the appropriate speed for
that height the drag (and therefore the thrust requirement) will be one
tenth of the weight, since in level flight lift must equal weight.
--
David CL Francis