Powertrain System Analysis for an Urban Air Mobility Tiltwing Concept Vehicle

In support of research and development for Urban Air Mobility (UAM) operations, the National Aeronautics and Space Administration (NASA) is developing a fleet of Vertical Takeoff and Landing (VTOL) concept vehicles. These vehicles aim to identify key areas for technological growth and provide reference data to the UAM community. A six-passenger Tiltwing concept recently added to the fleet offers new opportunities to explore the UAM design space through trade studies of power and propulsion systems. In this paper, a turboelectric powertrain is designed and analyzed using the Numerical Propulsion System Simulation (NPSS) tool, the NPSS Power System Library, and a new motor drivetrain optimization tool. Direct-drive and geared-drive powertrain architectures are designed, modeled, and compared across a UAM design mission. Sensitivity of the Tiltwing maximum takeoff weight to powertrain weights and efficiencies is estimated and used to inform optimal motor and gearbox selection. Results indicate that direct-drive and geared-drive configurations are comparable for this vehicle, with slight advantages to direct-drive for an unconstrained analysis. However, vehicle design constraints suggest advantages to a geared-drive system.