Lifting-Line Analysis of an Aircraft With a Bio-Inspired Rotating Empennage During Aerial Refueling

Aerial refueling is a common method used to extend the flight time of an aircraft. Many tanker aircraft currently in use utilize the flying boom refueling configuration in which a rigid, telescoping tube extends down to connect with a refueling aircraft. Due to the large contribution of the tanker's wingtip vortices to the flow field, the refueling aircraft can encounter significant forces, making it difficult to maintain position and potentially increasing fuel consumption. The lateral disturbances to the aircraft are mainly due to the interaction of the tanker's wingtip vortices with the vertical tail on the refueling aircraft. Rather than using a traditional vertical tail, the Bio-Inspired Rotating Empennage (BIRE) aircraft, uses a tail design similar to that of a bird in which the empennage rotates to provide yaw stability and control when needed. The purpose of this study is to use a numerical lifting-line method to compare the BIRE to a baseline aircraft with a vertical tail when in an aerial refueling flight configuration. Geometric models for the tanker, baseline, and BIRE are defined. Results are presented showing the velocity vector field of the flow field at a specified distance behind the tanker. For an untrimmed flight, an analysis is performed to compare the forces and moments encountered on the BIRE and baseline aircraft at various locations within the flow field. A trimmed analysis compares the resulting control surface deflections. Results show that the BIRE performs similarly to the baseline aircraft and would likely be able to maneuver at all locations for which the baseline is able to maneuver.