See Wikipedia:Drag polar and Wikipedia:Polar curve (aviation) for example.
These curves are not on a polar coordinate system. Why are they called polars?
It is an historical name.
The first polars were drawn by Otto Lilienthal in polar coordinates.
Here (sorry, German link) we find an example:
Sign up using Google
Sign up using Facebook
Sign up using Stack Exchange
5 months ago
Get the weekly newsletter!
see an example newsletter