What is the drag evolution with speed ? The general drag expression is in the form : Half rho v square, the dynamic pressure (we could also use rho_zero VC square, or point seven PS M square), multiplied by S and multiplied by the drag coefficient, CD_zero, the parasitic drag, plus K I CL square, the induced drag. When the vertical load factor is close to one, which happens in steady climb or descent and of course in level flight, the lift exactly balances the weight and we have CL equals mg over half rho v square S. So we can re-arrange the drag expression, and we can put it in the form : Drag equals : A CD_zero, a constant, multiplied by V square, which is the parasitic drag, and B KI M square, a constant also, divided by V square, which is the induced drag. Let's take a look to the corresponding curve. The first term, the parasitic drag, is just a portion of a parabola : we have here the speed, here the drag, and this is VS, the stall speed, which is our minimum speed. The second term, the induced drag, is like one over V two. It looks like a portion of an hyperbola, surging to infinity when speed comes close to zero. The reason is that the angle of attack, hence the lift coefficient, is very small at high speed, but increases quickly when approaching low speeds, as shown below the x-axis. The total drag is the sum of those two curves, dominated at low speeds by the induced drag, and at high speeds by the parasitic drag. One can easily demonstrate that for the maximum lift to drag ratio angle of attack, and, hence, for the corresponding speed, parasitic and induced drag have exactly the same value. And of course, as the lift is constant here, the maximum lift to drag ratio corresponds to the speed where the drag is minimum. So this is the evolution of drag when speed varies and load factor remains close to one. I say "close to" as in steady climb or descent, the load factor component Nza is indeed cos gamma, with gamma the flight path angle.