Multi-point aerodynamic optimisation of sailplane horizontal tailplanes

Abstract

A new horizontal tailplane for a high performance sailplane was developed through multi-point aerodynamic optimisation. This was achieved through the use of logged flight data, from which the operating spectrum of the horizontal tailplane of a specific sailplane was obtained. With the operating spectrum, a modified lifting line model implementing Xfoil and the Generalised Reduced Gradient optimisation algorithm were used to optimise the aerodynamic performance of the JS1-C 21m horizontal tailplane. Verification of the planform calculations was conducted with the commercial CFD software package Star-CCM+. The k - w SST turbulence and y - Reθ transition models were used for aerodynamic analysis in the verification process. The design of new horizontal tailplane tip sections was also performed with the use of CFD. Firstly the elevator span to horizontal tailplane span ratio best suited to the operating spectrum of the horizontal tailplane was evaluated. Secondly a wingtip shape proposed by Hoerner (1965) was implemented. The flight data-based multipoint optimisation of the planform of the horizontal tailplane shows appreciable performance increases compared to a baseline tailplane. Calculations show a 14% drag reduction for the tailplane over a sample flight. The tip design also shows a drag decrease of 1.1% at 150km/h and 3.3% drag decrease at 250km/h compared to the baseline tip section shape.