Flight Verification of Automatic Flight and Transition System for Lift/Cruise Thrust Type VTOL Aircraft

Abstract

The purpose of the present research is to develop and to demonstrate the design architecture of the AFTS (Automatic Flight and Transition System) for “Lift/Cruise Thrust” type VTOL (Vertical Takeoff and Landing) aircraft such as tilt-wing, tilt-propeller, tilt-duct aircraft, etc. VTOL aircraft of this type, characterized by propulsor installations that reorient the thrust relative to the aircraft, offer advantages of a wide flight envelope. However, flight and stability characteristics significantly change depending on airspeed and configurations such as wing tilt angles or propulsor orientations. These make it difficult to operate VTOL aircraft safely and the AFTS, which comprises both autopilot and auto-transition algorithm, should be developed to provide the safe and effective means to control the aircraft over its entire flight envelope. In this research, the autopilot was designed to provide control commands that change control strategies and gains according to the configurations. Additionally, the auto-transition algorithm, which should be coordinated with the autopilot, was designed to select and change configurations for accelerated and decelerated flight. The proposed AFTS was installed to a “Lift/Cruise Thrust” type, QTW (Quad Tilt Wing) VTOL UAS (Unmanned Aircraft System), and fully automated operation capability was demonstrated through flight test both in calm and windy conditions.