The German Aerospace Center (DLR) has equipped the PROTEUS uncrewed experimental aircraft with both a conventional and a morphing set of wings. Flight tests at the National Experimental Test Center for Unmanned Aircraft Systems in Cochstedt have already allowed DLR to test the functionality of the wings.

"The morphing wing can change its shape during flight, allowing it to adapt optimally to different flight conditions," explains project leader Martin Radestock from the DLR Institute of Lightweight Systems.

Both sets of wings are made entirely of fibre-reinforced composites. The morphing wing pair features a form-variable trailing edge section, made possible by a Hyperelastic Trailing Edge Morphing system (HyTEM), which enables the wing to deform seamlessly and without steps. "The HyTEM concept replaces conventional flaps and ailerons with an intelligent system comprising several small actuators distributed across the wingspan. These can precisely adjust the wing profiles at ten points without creating gaps between sections. The continuous shape reduces profile drag. In addition, lift, induced drag and aircraft control can all be influenced in a targeted manner – a major advantage for aerodynamics and flight mechanics," Radestock elaborates. Besides greater efficiency, this technology also promises improved safety as control functions can be distributed across the entire wing.

A central element of the project is an AI-assisted flight control system developed by the DLR Institute of Flight Systems, designed specifically to make full use of the unique movement capabilities of the morphing wing. During flight, the adaptive algorithm detects when the aircraft's actual behaviour deviates from its previously trained model and continuously adjusts its internal models. During training, specific damage scenarios and failures of individual control surfaces are also deliberately simulated. This allows the algorithm to learn to recognise such changes in flight and control the remaining actuators in a way that keeps flight behaviour as stable as possible. Unlike conventional flight control systems, this adaptive approach can optimally coordinate the many distributed actuators, making the most of the aerodynamic potential of the morphing structure while also improving fault tolerance.

A key element in this is the reliable method for reconstructing surface pressure distribution from just a small amount of measurement data. This capability, developed by the DLR Institute of Aerodynamics and Flow Technology for PROTEUS, gives the system an immediate 'sense' of its current flow field. The experimental aircraft can thus compare the reconstructed pressure field with the expected state, automatically detect local deviations and interpret them as relevant disturbances.

In initial trials, DLR researchers successfully tested both wing concepts in flight. They integrated both the reference wings and the newly developed morphing wings into the aircraft and tested them. The trials primarily served to demonstrate basic airworthiness and system integration, forming an important foundation for further measurement campaigns and investigations.

Although the researchers collected data during scaled flight tests, the aerodynamic and structural design, with a maximum speed of 300 kilometres per hour and a wing loading of 70 kilograms per square metre, is also relevant for light aircraft. To demonstrate scalability, DLR will conduct a flight test campaign in 2026 using PROTEUS with a total mass of approximately 70 kilograms. The findings will be developed further within the UAdapt (Unmanned Aircraft Wing Adaption) project.