Lift and Angle of Attack

In ,
David wrote:

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!


Similar thanks go to you. Dunno how that 'cubed' nonsense got in there. Call
it 'brain fade'...
Now let's see how much of this I remember in 6 month's time. ;-)



--
regards,

Mark