A new tiltrotor different from the old Europe is continuing with the development of its first tiltrotor, with progress made in reducing the aerodynamic drag of fuselage components. EU-funded researchers used comprehensive calculations to optimise geometries and quantify the effects on the design. Industrial Technologies © Thinkstock The Enhanced Rotorcraft Innovative Concept Achievement (ERICA) is a new type of air vehicle, presented as an alternative to helicopters, that combines vertical take-off and landing capability with high-speed cruise. The dual role of blades – as a helicopter rotor in hover and as a propeller in forward flight – results in a compromise in several aspects of the tiltrotor design. In particular, aerodynamics can be very important in the ERICA tiltrotor configuration and need to be extensively researched to improve both performance and safety. EU-funded researchers employed state-of-the-art computational fluid dynamics (CFD) models to study the fuselage geometry and used wind tunnel data for validation of the results. The CODE-TILT (Contribution to design optimization of tiltrotor components for drag reduction) project aimed to optimise overall tiltrotor efficiency by decreasing the drag force. The objective was twofold: to identify the optimum geometries that maximise the aerodynamic efficiency of individual components, and to evaluate the overall aerodynamic efficiency of the aircraft. To this end, the researchers performed simulations for various flight conditions on a scaled and full-sized rotor-free model of the ERICA fuselage. An extended sensitivity study was carried out to obtain reliable CFD models. For the model validation, experimental data were used from a wind tunnel campaign conducted within the Novel Innovative Competitive Effective Tilt Rotor Integrated Project (NICETRIP). Next, optimisation algorithms were coupled with CFD flow solvers to improve the aerodynamic efficiency of critical components of the tiltrotor fuselage by means of optimal shape design. Specifically, the researchers implemented an automatic optimisation chain and applied it to the wing-fuselage junction. The applicability of new drag reduction concepts, different from shape optimisation was assessed. The same numerical model applied for the wing-fuselage junction optimisation was used on the fuselage nose and the landing gear sponsons. The researchers studied in detail constraints on pilot visibility that need to be taken into account for modifications in the nose shape as well as aerodynamic moments of the overall tail-off configuration. Team members also searched for optimal configuration for the empennage, including both the fin and the horizontal tailplane. The main objective was to minimise aircraft drag without undesired lift reduction. Both empennage drag and lift forces were considered and, then, the effects of the shape optimisation on the overall aircraft aerodynamic performance were evaluated. CODE-TILT resulted in optimised geometries for several tiltrotor components, promising an overall reduction of aerodynamic drag up to 8 %. The new components manufactured according to the new designs will be tested either in a wind tunnel or in flight in the framework of the Green Rotorcraft Integrated Technology Demonstrator. Keywords Tiltrotor, aerodynamic, rotorcraft, wind tunnel, CODE-TILT, drag reduction
