Increasing the aspect ratio of the wing of an aircraft reduces drag and increases its range and endurance. However, a large wingspan complicates takeoff and landing. Therefore, an aerodynamics-driven monoplane–biplane morphing (MBM) aircraft was proposed, which cruises as a high-aspect-ratio monoplane and takes off and lands as a biplane, switching between two patterns during flight. This concept of MBM was validated in our previous work via wind tunnel experiments. We further develop it beyond this phase and introduce its applications under real flight conditions here. We constructed a test plane with a wingspan of 6 m and conducted a series of flight experiments on it. To examine its performance and facilitate its initial flight test, we built aerodynamic and dynamic models of the aircraft to analyze its morphing behavior through simulations. The corresponding controller algorithm and hardware system were also developed. The successful implementation of these systems enables bidirectional morphing during flight from a large-span monoplane to a half-span biplane. The test results, comprising data and photographs, validated the success of these trials. The concept of MBM, the corresponding models, and the control algorithm for morphing were thus verified.

The operation of aircrafts with high aspect ratio wings is usually vulnerable to low-standard airports and bad weather. A new concept for a mono-biplane aerodynamics-driven morphing aircraft is proposed. The movable and fixed wings form a biplane mode during takeoff and landing, while they form a high aspect ratio monoplane mode when cruising. This novel form of morphing can obtain a high cruise L/D while reducing nearly 50% of the takeoff and landing wingspan. However, the wing area is kept unchanged while morphing. The aerodynamic force on the movable wing is controlled by the deflection of the flaps to drive the morphing. No additional driving actuator is needed. In this way, although the morphing scale is large, the penalty on the complexity, structural strength, weight, and internal space of the wing is low. Taking the RQ-4A “Global Hawk” as the design baseline, morphing of the mono-biplane could further extend the cruise wingspan and aspect ratio for a better range without increasing the takeoff and landing span. When the wingspan was restricted, it was shown that this morphing scheme could reach a range extension of more than 50% when compared with an aircraft with the same wing load and different layouts. The feasibility of this mono-biplane aerodynamics-driven morphing concept was initially verified through ground vehicle tests. The possible influence of the morphing process on aircraft stability and control is also discussed.