ATTILA marks the first European research program in which a scaled tiltrotor model will be tested in Froude number scaled conditions with a potential towards Mach-scaled testing in heavy-gas, thereby providing the most realistic test environment short of full-scale flight testing. The knowledge and experience gained can be applied to upcoming novel aircraft development programs in Europe.
Contrary to past tiltrotor experimental research in Europe, the ATTILA testbed has been, as far as practicable, designed to be modular and scalable in order to facilitate future configuration changes and alternative test objectives or facilities. In this manner, the ATTILA testbed can be exploited by the Consortium to support the European tiltrotor research needs of the future.
In addition to the established aeromechanics codes that are used in the design phase, ATTILA aims to further the development of the novel VAST code. VAST is a coupled system of models that are expressed as state-space models wherein the implicit system of coupling equations is automatically resolved. This approach allows generic methods for solving the system to be developed and makes it suitable for general multi-model simulations. The multi-model capability, through minimizing the overhead of maintaining multiple codes, offers the benefit of reducing overall development costs for the industry.
The ATTILA testbed will employ fibre optic sensors for strain measurements in the rotating frame. Fibre optic sensors are used increasingly often in industrial strain sensing applications, but have not found their way into widespread use for wind tunnel testing applications. They provide a variety of benefits over conventional strain gauges, including immunity to electro-magnetic interference, superior fatigue characteristics, smaller interrogator electronics, etc. Fiber optic sensors can also be used for direct deformation measurements.
The ATTILA rotor will be fitted with contactless rotating power and data transfer in place of a traditional mechanical slip ring. The data is transferred in digital format, which simplifies the use of third-party data acquisition systems, such as fibre optic strain sensing systems and transfer of data to the main test data acquisition system. The technology can also be exploited for future novel smart/active rotor system developments where robust rotating data and power transfer is essential for operational applications.
Whereas tiltrotor whirl flutter stability testing has typically involved a process of excitation and free-decay measurements, the ATTILA testbed will feature online modal analysis to enable continuous state estimation and damping assessment, potentially without the need for direct excitation. As such, the technology promises faster testing and reduced complexity of the test setup.
The advanced multi-disciplinary design, manufacture, testing and validation techniques developed in the ATTILA project to understand and design for the whirl flutter phenomena associated with high-speed forward flight of tiltrotor aircraft are a necessary step in the development of the NGCTR and a key enabler for its successful introduction. Moreover, the experience gained and tools developed in ATTILA can be integrated in future novel aircraft developments and related test activities, improving innovation capacity in Europe.
