Sacramento, California based CR Flight is dedicated to building highly-efficient motor/propeller combinations based on contra-rotation – propellers turning contrary to one another. Not to be confused with counter-rotation – two propellers driven by two different engines and turning in opposite directions – contra-rotating propellers are driven in tandem by the same engine. In the case of CR Flight, they are driven by the same electric motor. Their web site shows a simple animation of the result. An instructive video provides details about the benefits and drawbacks of the concept. The firm’s mission statement gives a hint of its character. “CR Flight™ partners with established industry leaders to design, patent, license, manufacture and provide the industry’s only patented counter-rotating motors to UAV/drone commercial and consumer manufacturers and wholesale distributors. When you see the CR Flight™ name, know that the CR motor™ is manufactured under tight scrutiny for the highest quality.” Their web site shows their three current offerings, the V-10, …