Endurance increase by cyclic control

Applying the minimum principle, maximum endurance flight is considered as an optimal cyclic control problem with a state variable constraint. It is shown that a significant increase in the maximum endurance can be achieved by dynamic flight having an optimal cyclic control when compared to the best steady-state flight. The optimal altitude range within the flight envelope is determined. Furthermore, it is shown that the powerplant type represents a key factor when compared to other aircraft characteristics. From this, it follows that turbojettype engines have properties that can increase endurance via cyclic control. With regard to propeller-type powerplants, however, there appear to be no or only small improvements possible for the cyclic model con* sidered here. It is also shown that an increase in the maximum lift/drag ratio improves the cyclic control efficiency, which is more enhanced than steady-state flight efficiency.