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Old September 28th 03, 10:19 PM
David
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In article , Mark Cherry
writes

Sorry to be pedantic but, as far as I understand it, 'coefficients' are physical
constants. In this case, they are characteristics of a particular airframe.

True, they are, but the lift coefficient is a property at a given angle
of attack so they are characteristics of an airframe but only for a
given angle of attack. For small angles of attack then the lift
coefficient depends almost directly on the angle of attack.

The parasitic drag coefficient will go in proportion to a combination of frontal
area and total surface area (note that the frontal area presented to the
relative wind will change with variations in angle of attack, following a pitch
control input). The quantity of parasitic drag increases with the cube of the
airspeed, multiplied by this coefficient, mutiplied by the mass per unit time of
air flowing over it. (in kg.m.s-1 aka Watts, if I' m not mistaken)


Generally speaking parasitic drag depends on the square of the speed.
Power required depends on the cube of the speed.

Drag is a force, measured in Newtons or pounds force. Drag is a force;
watts are power.

The classic drag equation is
D = 0.5*(air density) * (reference area - usually wing area) *(
(velocity)^2) * (drag coefficient)

where velocity is TAS NOT IAS.

You seem to be confusing Power required with the drag force.

But I see Peter Duniho has already posted corrections!
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