Multidisciplinary Design of a Complex Tiltrotor Morphing Wing System

While aeromechanics and system element interactions for typical fixed- and rotary-wing aircraft are historically well defined, the complex aerodynamic interactions for tiltrotor aircraft introduces multiple added levels of complexity. This added complexity of an aircraft that operates with the properties of both a vertical takeoff and landing (VTOL) rotary-wing and a fixed-wing aircraft adds dimensions of analysis that are not typically found in other aircraft. Unique complexities arise due to architecture where a wing, used for lift in fast forward flight configuration, is located below a rotor, being used for lift in a VTOL configuration1. Here, the rotor downwash creates a lift-opposing force on the wing, termed 'download'. As such, model-based design and engineering approaches with parallel simulation and system design phases are required, in conjunction with a multi-disciplinary team, in order to solve the complex interactions during the design phases. Given the issue of download on the wings due to rotor downwash reducing fuel-efficiency during VTOL operations, a need to minimize this download arose. This necessitated the design of a system that would lower the download in VTOL and hover operations, while keeping the aerodynamic wing properties in airplane mode; a "morphing wing system" (MoWS). The basis of the morphing wing was to design a wing element which could articulate out of the rotor downwash in VTOL mode and articulate up into a standard wing configuration for aircraft mode. While these goals were unique to tiltrotor aircraft, they were in line with the European Union (EU) Clean Sky 2 (CS2) initiative to reduce CO2 emissions by 20-30% by increasing aircraft fuel efficiency. Since the least fuel-efficient phases of tiltrotor operations are during VTOL and hover, increasing efficiency in these phases, through the design and implementation of the morphing wing system, is shown to reduce overall high-speed VTOL (HSVTOL) operational CO2 emissions4. This paper presents the design of a morphing wing element applied to the Next Generation Civil Tiltrotor – Technology Demonstrator (NGCTR-TD), using a multi-disciplinary design team, in conjunction with the parallel use of a set of simulation models during the design phases. Given the complex interactions of the design, each model in the set took into account different aspects of the design and were integrated together to give a pseudo-live representation of the current design state, as it progressed through the iterative design loops. This led to a rapid design phase, culminating in the successful design of a morphing wing system that could reduce the download on the wing during VTOL and hover operations of a tiltrotor aircraft.