Embedded Files
Funded by the Air Force Research Lab
January 2020 - December 2025
Table of Contents
Project Overview
Birds control lateral maneuvers without a vertical tail. The goal of the present work is to evaluate whether aircraft can be controlled with a bio-inspired rotating empennage (rotating horizontal tail).
In theory, the forces and moments produced by the empennage can be summed to a single force vector and moment vector. By rotating a horizontal stabilizer and deflecting the elevator, the same force and moment vectors should be able to be created without a vertical tail.
Flight Simulation
We have developed a flight simulator to evaluate the static and dynamic stability and controls of the BIRE variant of the F-16 compared to the baseline aircraft.
V1.1: Full F-16 Simulator
January 2023
Features:
Updated aerodynamic model, including Prandtl-Glauert compressibility corrections
Direct surface / throttle control using keyboard, gamepad, or joystick input
Full HUD including flight path vector, radar altitude, mach number, and control surface indicators
Spring-damper landing physics using terrain ray casts
3rd person, cockpit, and toggleable alternate camera views
Aircraft
In preparation for testing the BIRE vehicle, multiple vehicles were tested to prove custom flight system hardware and software.
Volantex Phoenix
Flite-Test Explorer
Hobbyzone Aeroscout
E-flite F-16 80mm V2
BIRE
Flight Testing
103 Flights to Date
Volantex Flight Test #2
October 7, 2021
Purpose: Test retractable vertical stabilizer and rotating horizontal stabilizer.
Glider Flight Test #1
July 23, 2024
Purpose:
Test hardware, software, and ground station on simple aircraft
Verify pilot command response time
Verify ground station link and live plotting
Verify data logging on SD card and ground station
Outcome: Successful flight. All comms working correctly. Tested both manual mode and flight controller mode. Ground station link and live plotting worked correctly. Data logging onboard and on ground worked correctly. Landed a little too slow. Aircraft stalled just before touchdown. No damage to airframe or sensors. Some control surfaces are sticking due to construction. Will construct new glider for next flight.
Number of Flights: 1
Flight Time: 00:06:11
Glider Flight Test #4
September 18, 2024
Purpose:
Test rates controller
Outcome: Successful controller flights and data. Previous damage to the wing caused the spar to snap on the second flight leading to a crash.
Number of Flights: 2
Scout Flight Test #1
February 28, 2025
Purpose:
Test new flight controller design
Test new datalogging structure
Test on-board sensors
Test SRXL2 receiver protocol
Test new ground station
Acquire new vehicle information (trims, airspeeds, etc)
Outcome: RC signal interference believed to be caused by improper placement of antennas and telemetry module as well as cable management. Successful sensors.
Number of Flights: 1
Baseline Flight Test #1
April 11, 2025
Purpose:
Test flight controller on new aircraft
Test RC signal
Obtain trim values
Outcome: Lost RC signal leading to crash. Aircraft was fixed and flown in subsequent tests.
Number of Flights: 1
Baseline Flight Test #2
April 14, 2025
Purpose:
Test flight controller
Test RC signal (SRXL2)
Test thrust reversing
Outcome: RC signal issues fixed by better antenna placement, removing the telemetry module, and adding a satellite receiver. Thrust reversing worked well. Nose gear slipped a gear on initial flight leading to issues on landing in subsequent flights.
Number of Flights: 4
Baseline Flight Test #3
April 22, 2025
Purpose:
Test flight controller
Test RC signal (SRXL2)
Test thrust reversing
Practice landings
Obtain trim values
Outcome: No RC link issues. Odd right roll tendency on takeoff. Successful flights.
Number of Flights: 2
Scout Flight Test #14
September 1, 2025
Purpose:
Test EKF estimates and controllers with new sensor configuration
Outcome: EKF estimates and controller performance good. Magnetometer needs calibrated.
Number of Flights: 3
Baseline Flight Test #4
September 23, 2025
Purpose:
Test EKF estimates and controllers with new sensor configuration
Test controller without Vxb sensing.
Outcome: EKF estimates and controller performance good. Magnetometer needs calibrated. Could use faster response in roll for controllers.
Number of Flights: 1
Baseline Flight Test #5
October 1, 2025
Purpose:
Test EKF estimates and controllers.
Test controller without Vxb sensing.
Test new magnetometer calibration.
Outcome: Good EKF estimates and controller performance in flight 1, but not flight 2. Discovered initialization issue with EKF.
Number of Flights: 2
Baseline Flight Test #6
October 9, 2025
Purpose:
Test EKF estimates from PX4 with controllers.
Outcome: Good EKF estimates. Controllers need tuned for oscillations. Airspeed measurement wrong inside PX4.
Number of Flights: 1
Baseline Flight Test #7
October 11, 2025
Purpose:
Test EKF estimates from PX4 with controllers.
Solve controller oscillations
Outcome: Good EKF estimates. Found mapping error resulting in control surfaces causing oscillations.
Number of Flights: 5
Baseline Flight Test #7
October 11, 2025
Purpose:
Test EKF estimates from PX4 with controllers.
Solve controller oscillations
Outcome: Good EKF estimates. Found mapping error resulting in control surfaces causing oscillations.
Number of Flights: 5
Baseline Flight Test #11
October 21, 2025
Purpose:
Test pop-up tail's stability when deployed.
Test modified control law with pop-up tail.
Outcome: Pop-up tail created enough stability, but a lot of left roll tendency. Successful flight 1. Flight 2 lead to crash due to loss of orientation. Telemetry modules lost connection throughout flights due to tail interference.
Number of Flights: 2
Baseline Flight Test #12
November 13, 2025
Purpose:
Test pop-up tail's stability when deployed.
Test modified control law with pop-up tail.
Test aileron trim.
Outcome: Aileron trim perfect for counteracting tail's roll moment. Pop-up tail created enough stability. New telemetry radios maintained link throughout flight. Controllers were successful where a little faster roll response could be needed.
Number of Flights: 1
Publications
Journal Publications
Stabilizing a Bio-Inspired Rotating Empennage Fighter Aircraft in Multiple Trim Scenarios
Moulton, B. C., Harris, M. W., and Hunsaker, D. F., “Stabilizing a Bio-Inspired Rotating Empennage Fighter Aircraft in Multiple Trim Scenarios,” Journal of Guidance, Control, and Dynamics 2025, 48(3), 520-536. DOI: 10.2514/1.G008456
A Review of Avian-Inspired Morphing for UAV Flight Control
Harvey, C., Gamble, L. L., Bolander C. R., Hunsaker, D. F., Joo, J. J., and Inman, D. J., "A review of avian-inspired morphing for UAV flight control," Progress in Aerospace Sciences, 2022, 27 pages, DOI: 10.1016/j.paerosci.2022.100825
Conference Publications
Evaluation of Stability and Controllability of the Multiple Trim Solutions for a Bio-Inspired Rotating Empennage Fighter Aircraft
Moulton, B. C., Bolander, C. R., and Hunsaker, D. F., “Evaluation of Stability and Controllability of the Multiple Trim Solutions for a Bio-Inspired Rotating Empennage Fighter Aircraft” AIAA SciTech 2025 Forum, January 2025, AIAA-2025-0662 DOI: 10.2514/6.2025-0662
Evaluation of First-Order Actuator Dynamics and Linear Controller for a Bio-Inspired Rotating Empennage Fighter Aircraft
Moulton, B. C., Harris, M. W., Hunsaker, D. F., and Joo, J. J., “Evaluation of First-Order Actuator Dynamics and Linear Controller for a Bio-Inspired Rotating Empennage Fighter Aircraft,” AIAA SciTech 2024 Forum, January 2024, AIAA-2024-2649 DOI: 10.2514/6.2024-2649
Attainable Moment Set and Actuation Time of a Bio-Inspired Rotating Empennage
Bolander, Christian R., et al. "Attainable Moment Set and Actuation Time of a Bio-Inspired Rotating Empennage." AIAA SCITECH 2022 Forum. 2022. DOI: 10.2514/6.2022-1670
Static Trim of a Bio-Inspired Rotating Empennage for a Fighter Aircraft
Bolander, C. R., Kohler, A. J., Hunsaker, D. F., Myszka, D., and Joo, J. J., “Static Trim of a Bio-Inspired Rotating Empennage for a Fighter Aircraft,” AIAA SCITECH 2023 Forum, 2023, p. 0624. DOI: 10.2514/6.2023-0624
Linearized Rigid-Body Static and Dynamic Stability Of An Aircraft With A Bio-Inspired Rotating Empennage
Kohler, A. J., Bolander, C. R., Hunsaker, D. F., and Joo, J. J., “Linearized Rigid-Body Static and Dynamic Stability Of An Aircraft With A Bio-Inspired Rotating Empennage,” AIAA SciTech 2022 forum, 2022, DOI: 10.2514/6.2023-0621
Theses and Dissertations
Controllers and Control Insights for a Bio-Inspired Rotating Empennage Fighter Aircraft
Moulton, Benjamin C., "Controllers and Control Insights for a Bio-Inspired Rotating Empennage Fighter Aircraft" (2025). All Graduate Theses and Dissertations, Fall 2023 to Present. 510.
Aerodynamic Implications of a Bio-Inspired Rotating Empennage Design for Control of a Fighter Aircraft
Bolander, Christian R., "Aerodynamic Implications of a Bio-Inspired Rotating Empennage Design for Control of a Fighter Aircraft" (2022). All Graduate Theses and Dissertations. 8749.
Linearized Rigid-Body Static and Dynamic Stability of an Aircraft With a Bio-Inspired Rotating Empennage
Kohler, Austin J., "Linearized Rigid-Body Static and Dynamic Stability of an Aircraft With a Bio-Inspired Rotating Empennage" (2022). All Graduate Theses and Dissertations. 8675.
Students
PhD
Christian Bolander
Ben Moulton
MS
Austin Kohler
Ashton Gilbert
Kathle Tischner
Undergraduate
Spencer Adams
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