The ATTILA project is aimed at the design, manufacture and testing of an advanced testbed for aeroelastic wind tunnel testing of tiltrotor aircraft. The testbed will consist of a suitably instrumented aeroelastically scaled cantilevered half-wing with powered nacelle-proprotor system representative of the full-scale NGCTR-TD design. Advanced fiber optic sensor and contactless rotating power and data transfer techniques will be used. The design process, coupled with test iterations, is supported by detailed structural and aeroelastic simulations using a range of complementary codes. The ATTILA testbed will first be subjected to a wind-on shakedown test in the DNW LLF 6x6m test section in Froude scaled conditions. After the system functionality and structural dynamic characteristics have been verified, a second data gathering test will be performed in the NASA TDT heavy-gas transonic dynamics wind tunnel in simultaneous Froude and Mach scaled conditions, selected as subcontractor to NLR for its unique worldwide capability of meeting the full test requirements in terms of aeroelastic scaling capability, test Mach number, and model size. Testing will be performed in three mass/stiffness configurations covering 3×25 test points with test speeds up to the NGCTR-TD whirl flutter speed (at least M = 0.56). The proposed test campaign provides the highest possible fidelity experimental demonstration of the whirl flutter characteristics of the NGCTR-TD prior to high-speed flight testing in 2024-2025. Its productivity and safety will be ensured through the introduction of real-time modal damping analysis. The post-test data analysis phase includes a test-to-code correlation study in which the analytical models derived by the consortium are validated against the test results. Engaging a significant subcontractor (NASA), this 54-months €6,525,261 valued action is composed of 2 research centres (NLR, DLR), 1 non-profit foundation (DNW), 1 university (POLIMI) and 1 SME (Technobis).