Surface Tolerances for Aircraft Design, Maintenance and Repair

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The aerodynamic design of aircraft surfaces is subject to many constraints and is refined interactively during the design cycle. One of the constraints is the manufacturing tolerance at joints, surface roughness/waviness and gaps. During the design phase acceptable tolerances are set by the aerodynamic department to minimize their effect on performance and fuel burn. The current methods only estimate the excrescence drag and are based on the interpretation of results from surface discountinities placed in a zero pressure gradient. Therefore these methods do not consider effects on lift and pitching moment. This project will develop and validate rapid CFD-based tools that capture these effects over a wide range of surface shapes and flow conditions, and consequently more accurate data sheet methods. These methods will enable the designer to trade surface-finish requirements between performance benefits and manufacturing costs and thus reduce total-ownership costs. In addition the results from this project will be tailored to provide information to operators to assist in their maintainance in order to minimise the increase in fuel burn due to ageing aircraft.