Proprotor–wing aerodynamic interaction in the first stages of conversion from helicopter to aeroplane mode

Tiltrotors have the potential to revolutionise air transportation since they combine the flight performance of aeroplanes with the versatility of helicopters. One of the most crucial features characterising tiltrotors is represented by the aerodynamic interaction between wing and rotor. Although this phenomenon has been largely studied using both experiments and calculation, analyses were mainly focused on helicopter operative mode and hovering condition. The present work is aimed at describing the effects due to the aerodynamic interference between wing and rotor of a tiltrotor aircraft employing the tiltwing concept solution during the first stage of the conversion manoeuvre from helicopter to aeroplane configuration. Experimental tests carried out in the open test section of the Politecnico di Milano Large Wind Tunnel with a half-span scaled powered model are reported in detail and results are illustrated in terms of rotor performance and wing aerodynamic loads. Both isolated rotor and half-span model test results are presented as function of several parameters. Overall aircraft performance during the first part of the conversion manoeuvre is finally discussed.