Aeroelastic Test of the Nixus FBW Sailplane

Nixus is the world’s first fly-by-wire (FBW) sailplane, with a custom 92-foot span, 53.3 aspect ratio wing. With the second-largest-aspect-ratio wing ever built for a crewed airplane, Nixus faces unique challenges for aeroelastic design, requiring detailed study and special considerations for safe operation. The use of an FBW system for the wing control surfaces allows the exploration of new strategies for automatic flap positioning, tailored aileron deflections, load alleviation, and, in the future, aeroelasticity control. This paper briefly describes some aspects of this sailplane’s fabrication and covers in detail the ground vibration test (GVT) and use of the GVT results in the flight envelope expansion campaign. The preparation and execution of the GVT are presented, including aspects related to the involvement of Cal Poly’s Aerospace Engineering undergraduate students in this process as part of an extracurricular activity. Results of the GVT, comparison with finite element analysis (FEA), and flutter predictions from the test-verified FEA model are provided. Additionally, the execution of flutter flight tests that used the FBW system to excite the wing is presented.