Low-Speed Flight Testing and System Identification of a Small-Scale Supersonic Uncrewed Aerial Vehicle

Abstract

The University of Calgary’s Multipurpose Uncrewed Fixed-wing Advanced Supersonic Aircraft (MUFASA) program intends to advance open knowledge of small-scale supersonic uncrewed aerial vehicle (SSUAV) aerodynamics using novel, air-breathing propulsion. Continued MUFASA development relies on a lightweight, downsized demonstrator possessing satisfactory low-speed stability and control characteristics. Following an iterative prototype development program, sustained flight of a second-generation demonstrator was achieved. Comprehensive development consisted of: modular design and fabrication; ongoing geometry, inertia, and power accommodations; and semi- and fully autonomous flight testing to acquire state, control and positioning data. Variation in static margin, and control surface trim and deflection limits contributing to successful tests were documented. A system identification with multivariate least-squares linear regression was performed with maneuver-specific autonomous data, invoking orthogonal functions as dictated by collinearity. A set of 25 local aerodynamic coefficients were estimated from regression to construct linearized models describing the aircraft’s non-dimensional aerodynamic forces and moments as functions of state and control derivatives. A comparison of coefficients to computational fluid dynamics estimates generally supports positive static and dynamic stability. Conspicuous differences help to identify longitudinal overdamping and poor elevator authority for the current center of gravity placement with presently sized control surfaces. A limited comparison to a six degree-of-freedom mathematical model over brief segments of flight data, applying the generated coefficients, shows satisfactory local agreement in aircraft attitude prediction, but inconsistent angular rates and moment damping. Unsustained flight attempts highlight sensitivity to environmental disturbances causing asymmetric flow effects, preceding lateral and directional destabilization. Sustained flight has qualified the current MUFASA version for future high-speed testing, subject to further refinement of maneuverability and control.