Static Trim of a Bio-Inspired Rotating Empennage for a Fighter Aircraft

Future tactical aircraft will likely remove the vertical tail to leverage the benefits to efficiency and weight. Many species of birds control their flight without a vertical surface by rotating their tails. This work details an analysis on a bio-inspired rotating empennage (BIRE) control system that operates similarly to a bird’s tail. An aerodynamic model is presented for the baseline fighter aircraft and a variant of the aircraft employing the BIRE control system. To analyze the trade-off between longitudinal and lateral control in static trim, we analyzed two trim scenarios for each aircraft: the steady, coordinated turn and steady-heading sideslip. These trim conditions were analyzed at several flight conditions that were identified to be important in a fighter aircraft flight envelope. Our analysis shows that the BIRE control system is able to replicate the trim capabilities of the baseline aircraft, though sharp changes in control surface deflections were required to trim the aircraft with the center of gravity at its nominal position. This could prove to be significant when designing a control system to provide stability to the BIRE variant through active damping. The BIRE was shown to have a chance of tail strike in certain landing scenarios when landing in steady-heading sideslip. An analysis of the dynamic behavior and control of the BIRE variant will be required before final conclusions on the possibility of tail strike can be drawn.