Aerodynamic optimisation of wings in multi-engined tractor propeller arrangements

Aerodynamic optimisation of wings in multi-engined tractor propeller arrangements is discussed and analysed with a fast calculation based on a Trefftz-plane analysis where the conservation laws of mass, momentum and energy are fulfilled in a control volume surrounding the configuration. The paper discusses the formulation of the optimisation algorithm based on augmented Lagrange integrals. The effect of viscous effects is incorporated in the calculation process. The method was implemented in a computer program which enables the user to find the optimum lift distribution for minimum drag for any tractor propeller/wing arrangement of arbitrary shape. As input for the slipstream data the user can either select input of experimental data or generate artificial data using a simple slipstream model based on the well-known blade element theory with Prandtl tip loss factor. Some numerical studies show that optimisation of a modern medium speed turboprop aircraft leads to performance increase by adapting the wing shape.