  Fixed-wing vertical take-off and landing (VTOL) aircraft pose a unique
control challenge that stems from complex aerodynamic interactions between
wings and rotors. Thus, accurate estimation of external forces is indispensable
for achieving high performance flight. In this paper, we present a composite
adaptive nonlinear tracking controller for a fixed-wing VTOL. The method
employs online adaptation of linear force models, and generates accurate
estimation for wing and rotor forces in real-time based on information from a
three-dimensional airflow sensor. The controller is implemented on a
custom-built fixed-wing VTOL, which shows improved velocity tracking and force
prediction during the transition stage from hover to forward flight, compared
to baseline flight controllers.
