The LLARA project investigated two key aspects of electro‑mechanical actuators (EMAs) that currently limit their use in primary flight control (PFC) of large transport aircraft. The first focus was the development of an actuator‑based structural load‑reduction function for the aileron EMAs of a future short‑ to medium‑range aircraft. The concept relies on the ability of EMAs to modulate the stiffness of the position‑control loop, thereby reducing gust‑induced bending moments without the need for active aileron deflections. A simulation study of the EMA model and the control concept was performed, revealing that the initial design required refinement to improve position accuracy and robustness against the highly variable friction of the EMA. After optimisation, the EMA model was integrated into an aero‑elastic simulation of a generic aircraft. Gust inflows at various flight states were simulated, and the resulting load histories on the wing structure and the aileron were evaluated. For the design‑flight condition at the design speed (v_c) and Mach number (M_c), the load‑reduction function reduced the amplitude of the bending moment at the wing root by 2.0 %. A further pole analysis of the full system dynamics at high Mach numbers showed that the aero‑elastic stability was maintained both with and without the load‑reduction function. These results demonstrate that a locally applied EMA‑based load‑reduction can be effective, responsive, and potentially cheaper than a global active load‑reduction system, because it eliminates the need for additional sensors such as accelerometers or LIDAR.

The second major objective of the DLR within LLARA was the exploration of sensor‑minimal and fault‑tolerant control strategies for EMAs. Virtual sensors based on analytical redundancy were proposed to reduce hardware complexity, thereby lowering weight, cost, and critical dimensions such as build volume. The project aimed to develop a comprehensive concept, implement suitable controller modes, and validate the approach on a test rig. Particular attention was given to the possibility of a resolver‑less position control of the EMA, relying on linear variable differential transformers (LVDTs) and model‑based estimation. The expected outcome was a control architecture that maintains high positioning accuracy while tolerating sensor failures, which is essential for the reliability required in primary flight control.

The LLARA consortium comprised the German Aerospace Center (DLR) together with major aircraft manufacturers such as Airbus, Boeing, and COMAC. DLR’s role focused on the technical development of the EMA load‑reduction concept and the sensor‑minimal control strategy, while the industry partners contributed expertise in aircraft integration and validation. The project concluded with a final report dated 21 June 2023, summarising the technical achievements and their relevance for future EMA applications in large transport aircraft. The work is intended to inform subsequent EMA projects across the industry, demonstrating that the integration of advanced control and monitoring algorithms can meet the stringent life‑time, cost, and weight requirements of primary flight control systems.