Simultaneous Optimization of the Airframe, Powerplant, and Operation of Transport Aircraft

Global optimization of transport aircraft is performed to minimize fuel burn for a specified mission. The design space includes the geometry, wing airfoils, primary structure, engine size and cycle parameters, and the flight profile parameters. The method employs a number of physics-based models for structural sizing and weight estimation, viscous CFD for all major aerodynamic components, and a component-based turbofan simulation. The models drive a trajectory integration to calculate mission fuel burn. These physics-based models mostly eliminate the reliance on historical weight and engine performance correlations and wetted-area drag prediction methods, and hence give confidence for development of radical transport aircraft which fall outside of historical trends. Computed examples show a D8.x aircraft series to replace the Boeing 737-800, with up to 49% less fuel burn using today’s alumimum technology, and up to 71% less fuel burn using year 2030 forecast technology. These exploit a novel fuselage configuration via its indirect effects on structural weight, lift to drag ratio, and propulsive efficiency, all captured by the collection of coupled low-order models. Sensitivity of the fuel burn to cruise Mach number change, materials allowables improvements, and span constraints is also investigated.