Region of reverse command

[Stby One]

Well, while it is generally true that the region of reverse command falls below L/D max, the technical definition is when the speed drops below the best endurance speed. The best endurnace speed is actually a little slower than the speed found at L/D max. So theoretically, a small range of speed below L/D max actually occurs within the region of normal command.

You're absolutely right. Its the power/required power curve(s) that's interesting when you talk about pistons (or propeller aircraft)

For a Jet though its also max endurance, however since the Jet engines "power" output is mesured as a force (thrust) it's the lowest point on the drag curve that's interesting (max L/D)

 

[Goose Egg]

I think it's important to remember that the Power [Required] Curve is not a drag curve, and that the two do not neccessarily correspond, even though drag itself has a large influence on the actual power required. For example, while L/Dmax is the low point on a drag curve, it is the tangent point on the power curve with a line drawn from the origin. (The low point on a PR curve is max endurance, or min sink for you glider guys.)

Therefore, being "behind the power curve" or in the "region of reversed command" pertains to when power required begins to increase with a decrease in airspeed, and not necessarily to L/D max or Min Sink per se.

Source: Flight Theory for Pilots, Charles E. Dole, page 108

-Goose