Performance enhancing elements for an 18 m-Class glider

Abstract

The development history of aircraft can be seen as the quest for improved performance. This is also true for gliders where the aim is to design gliders that can fly faster and further than their predecessors. Improvements in terms of performance have often been associated with a decrease in handling qualities and stability. This usually results in a glider-pilot system that performs sub-optimally due to pilot fatigue and distractions induced by poor handling qualities. The design for higher performance should therefore be viewed as an integrated design problem pertaining to aerodynamic improvement as well as aircraft handling qualities. During the development of the JS1 glider, four performance-enhancing elements were suggested and implemented in order to improve its performance beyond the current state-of-the-art. These include, firstly, the use of spanwise tailored airfoil sections, each optimized for the average Reynolds number over the particular section of the wing. The second element is the use of active boundary layer control on the wing of the glider. The third element is the use of a new cockpit air extractor that will allow for the stabilization of the boundary layer on the fuselage. The last element is a control system design approach that allows the glider to be designed for easy handling characteristics. Each of these performance enhancing elements was investigated in detail and the effect of each was validated by verified calculation methods, wind tunnel testing or in-flight testing. It was found that spanwise tailored airfoil sections can increase the overall performance of an 18 m-Class glider by 0.5 percent. Active boundary layer control on the wing, as defined in the context of this thesis, can result in a gain of 1.8 percent. The cockpit extractor has the potential for a 3.5 percent gain. A total performance gain of 5 percent is therefore possible over the current state-of- the-art. The effect of handling qualities on the glider-pilot system performance was quantified through a questionnaire to JS1 pilots. This showed that the integrated design approach has resulted in a glider with not only a high aerodynamic performance, but also with exceptional handling qualities. Most of the performance-enhancing elements have already been implemented on the production JS1 gliders with the exception of the active boundary layer control on the wing. At the 2010 World Gliding Championships in Hungary, four of the top ten places were achieved by pilots flying JS1 gliders.