Airspeed Forward-Invariance for Unpowered Fixed-Wing Aircraft
For autonomous fixed-wing aircraft operating unpowered, this provides a principled method to ensure airspeed safety under wind, addressing a critical gap in guidance-level protection.
This paper derives closed-form, wind-dependent conditions for airspeed forward invariance in unpowered fixed-wing aircraft using Nagumo's tangency condition, and embeds them in an offline quadratic programming framework to certify safe maneuver primitives. Validation on high-fidelity gliding trajectories demonstrates strict airspeed boundedness.
Autonomous fixed-wing flight is becoming a key capability in aerial robotics, enabling sensing, mobility, and contingency operations across both small-scale Uncrewed Aircraft Systems and large-scale Advanced Air Mobility. During unpowered operation in fixed-wing platforms, airspeed is regulated solely through potential-kinetic energy exchange, making airspeed dynamics highly sensitive to guidance commands, particularly under wind. This paper presents a viability-based airspeed protection for ground-referenced guidance in steady wind, where airspeed evolution depends explicitly on the commanded flight path angle. Leveraging Nagumo's tangency condition, we derive a closed-form, wind-dependent characterization of admissible guidance commands that guarantees forward invariance of a safe airspeed envelope. These conditions are embedded within an offline quadratic programming framework to certify airspeed-safe maneuver primitives for non-ascending flight at the guidance level. The approach is validated using a high-fidelity unpowered fixed-wing aircraft model on gliding trajectories formed by concatenating certified maneuver primitives, demonstrating strict airspeed boundedness. Future work will address unsteady wind fields and flight experiments.