An Application of the Carson Cruise Optimum Airspeed-A Compromise Between Speed and Efficiency 850867

It is well known that, for propeller-driven airplanes, maximum fuel economy occurs at maximum L/D ratio. It has been shown that, while the speed for maximum L/D yields the least fuel consumed per unit of distance, there is also a speed for the least fuel per unit of velocity, essentially, the best compromise between speed and fuel economy. This paper presents a simple method to predict this optimum airspeed in terms of calibrated airspeed. In this form, it is only a function of gross weight and could easily be made available in operating handbooks in the form of two-dimensional charts. It is shown that the optimum airspeeds for the range of normal operating gross weights requires fairly normal cruise power settings. The study further describes a simple, straightforward method of arriving at the relationship of cruise optimum airspeed in terms of maximum L/D speed.