NOMENCLATURE C D drag coefficient measured by main balance C Dref drag coefficient measured by main balance for complete aircraft at zero incidence angle C Dtilt drag coefficient measured by tilting wing balance C M pitching moment coefficient measured by main balance C Mref pitching moment coefficient measured by main balance for complete aircraft at zero incidence angle C Mtilt pitching moment coefficient measured by tilting wing balance C N yawing moment coefficient measured by main balance C Nref maximum absolute C N measured by main balance for complete aircraft with V2 fin C N t yawing moment coefficient measured by tail balance GVPM Politecnico di Milano Large Wind Tunnel MB main balance RHW right hand tilting wing TB tail balance V1 small fin V2 large fin α model incidence angle β model sideslip angle ABSTRACT A wide aerodynamic test campaign has been carried out on the tiltrotor aircraft ERICA at the Large Wind Tunnel of Politecnico di Milano by means of a modular 1:8 scale model in order to produce a dataset necessary to better understand the aerodynamic behaviour of the aircraft and to state its definitive design. The target of the tests was the measurement of the aerodynamic forces and moments in several different configurations and different attitudes. The test program included some conditions at very high incidence and sideslip angles that typically belong to the helicopter- mode flight envelope and measurements of forces on the tail and on the tilting wings. A large amount of data has been collected that will be very useful to refine the aircraft design. In general the aircraft aerodynamics do not present any critical problems, but further optimisation is still possible. From the viewpoint of drag in the cruise configuration, the sponsons of the landing gear seem to be worth some further design refinement since they are responsible for a 20% drag increase with respect to the pure fuselage configuration. On the contrary, the wing fairing has proved to work well when the aircraft longitudinal axis is aligned with the wind, providing just a slight drag increase. Two other interesting aspects are the quite nonlinear behaviour of the side force for the intermediate sideslip angles as well as the noticeable hysteresis in the moment coefficient at very high incidence angles. THE AERONAUTICAL JOURNAL MAY 2011 VOLUME 115 NO 1167 315 Paper No. 3548. Manuscript received 26 February 2010, revised version received 21 September 2010 accepted 15 December 2010. Wind-tunnel tests of a tilt-rotor aircraft G. Gibertini giuseppe.gibertini@polimi.it F. Auteri, G. Campanardi, C. Macchi and A. Zanotti Dipartimento di Ingegneria Aerospaziale Politecnico di Milano, Campus Bovisa Milano, Italy A. Stabellini AgustaWestland, Helicopter System Design Italy https://doi.org/10.1017/S0001924000005790 Downloaded from https:/www.cambridge.org/core. Open University Library, on 10 Feb 2017 at 17:52:12, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms.