Impact of aerodynamic surface tolerance on aircraft cost driver

The cost impact of aerodynamic tolerances on the wetted surface of an engine nacelle is considered. Manufacturing tolerance data were obtained from Bombardier Aerospace Shorts, Belfast, while the corresponding costs were calculated according to various recurring elements such as basic and overtime labour, rework, concessions, redeployment, etc., along with amortized non-recurrent costs due to jigs and tooling, machinery, etc. The cost-tolerance relations were modelled statistically so that the influence of tolerance change could be ascertained. It was found that relatively small tolerance relaxations resulted in significantly reduced costs of production but that there was a large variation in the sensitivity, at current levels. The resultant drag penalty was also predicted in conjunction with the cost-tolerance estimation to show that the operational cost effectiveness of the nacelle was increased by 0.33 per cent.