Abstract:

Various estimates of the aerodynamic penalty due to an upper surface rear spar repair plate using Viscous Full Potential (VFP) wing/body method with excrescence modelling, ESDU 75031 and ESDU ASTEROID are presented. These include the VFP method, which has the advantage of capturing the additional effects of the repair plate on wave and vortex drag, lift and pitching moment which the other methods such as ESDU 75031 and ESDU ASTEROID cannot do. In this case the excrescence is on the upper surface, the VFP method predicts a small lift loss which is sufficient to increase the drag penalty at constant lift coefficient. This increase is two times the drag predicted by ESDU 75031 and ASTEROID which results in significant increase in fuel and cost when taken over an annual utilisation for a typical single aisle aircraft similar to Airbus A320/Boeing 737.

The TM also shows that the VFP output can be used to provide user defined data for the ASTEROID flat plate option. This demonstrates that VFP provides the flexibility for users to define the flow over their own geometries, thereby removing the need to use the ESDU data and various aircraft/wing geometries provided. However, the ASTEROID tool both flat plate and full package can be used to provide an initial investigation into repairs/manufacturing tolerances to look at the sensitivity of the excrescence shape/size/edge treatment on drag before further investigations using VFP.

See also:

• ESDU ASTEROID : Aircraft Surface Tolerances for Enhanced Repair, Operations and Design