Power Efficient Trim Solutions for the Hybrid Wing Body in Approach Conditions

Abstract

The presence of control redundancy in configurations such as the Hybrid Wing Body can result in non-unique trim trim solutions. This can be taken advantage of to minimize a secondary metric in addition to balancing the forces and moments acting on the vehicle. In a previous study, drag was investigated as a secondary metric and was found to work well for several flight conditions. For the approach flight condition, however, the minimum drag solution was found to require a thrust below an assumed approach idle throttle. A different metric must be used in the presence of an active throttle constraint during optimization. Actuation power requirements are known to be a subject of much uncertainty and high risk for the Hybrid Wing Body configuration. Trim solutions that help keep actuation power requirements low are therefore worth investigating. A metric based on control surface hinge moments was developed and used for trim optimization analyses. Under the assumption of electrical actuation systems, it can be used as a stand-in for steady state power in early design phases. The metric was successfully used to identify trim solutions that will likely have low steady state power requirements. The optimizer was able to achieve low power trim solutions by allowing several elevons to float to their neutral hinge moment positions, while using a single pair of elevons to trim the remaining pitching moments. The sensitivity of the minimum power trim solution to deflection limits and the use of trim-only devices was also investigated.