The term “polar” refers to the polar curve, which is a graphical representation of an aircraft’s performance characteristics. In aviation, the most common polar curve is the lift coefficient versus drag coefficient curve, often referred to as the “lift-drag polar.”
Cd = Cd0 + (Cl^2 / (π * e * A))
- Cd: Total drag coefficient, which combines both parasite drag (Cd0) and induced drag (dependent on lift coefficient).
- Cd0: Parasite drag coefficient, which represents the drag caused by the shape of the aircraft, surface friction, and other non-lift-related factors. It’s a constant term that contributes to drag even when there’s no lift.
- Cl: Lift coefficient, which indicates the amount of lift generated by the aircraft’s wings.
- π: Pi, approximately 3.14159.
- e: Oswald efficiency factor, a dimensionless parameter that takes into account the aircraft’s lift distribution and wing span efficiency. It’s typically a value between 0.7 and 1.0.
- A: Wing aspect ratio, which is the ratio of the wing’s span to its average chord (width).