Manu Skytt? wrote:
"William W. Plummer" wrote in message news:rbc6d.169436$3l3.20749@attbi_s03...


What feature of the polar curve are you looking for? Stall speed is
listed separately as is best glide. The peak of the curve doesn't tell
much although it is close to best L/D. What are you trying to figure?


What I am trying to figure is a parabolic estimation of the polar
curve in different phases of flight (climb, cruise and approach). So
that means CD0 and K are the factors to be calculated. Polar curves in
form of L/D vs. CL or CD vs. CL (or CD vs. CL^2) will also do.
Naturally more precise estimation of the polar curve is even better.

The results (polar curve equations) will be used in my OFP program
which optimizes flight time and consumed fuel. Input is the route and
wind at different altitudes. Output is cruising altitude and power
setting for every leg in addition to normal OFP outputs. The program
also gives you the point to leave your cruise altitude.

Right now I am using POH values for climb time, climb fuel, fuel
consumption, cuise TAS etc. for every 2000 ft. In between I am using
linear approximation for those values. It means that the curves for
flight time and consumed fuel as a function of altitude are not as
smooth as I would like them to be. Therefore I would like to try
parabolic estimation of polar curves to calculate the same values.

I'm out of my league here, but intuitively it seems that flying at the
best glide speed is best for fuel consumption because that's where the
airframe is robbing the least kinetic energy and turning it into heat.
The fact that the aircraft is powered is irrelevant, you just want it to
be efficient. You can pick off the best glide speed graphically --
it's where a line from the origin is tangent to the polar. With sink
rate on the Y-axis and airspeed on the X-axis, you want to minimize the
slope of that line. The airframe must be somewhere on the polar with
speed determining exactly where.