An estimate of the effect of underwing nacelles on the aerodynamic efficiency of a supersonic transport aircraft

For a Mach mumber near 2 the maximum cross-sectional area of a turbo-jet nacelle in general still exceeds the intake area. If this surplus area cannot be buried within the basic configuration adding the nacelle is likely to increase the drag. By mounting the nacelle on the under-surface of the configuration some of the resulting loss in aerodynamic efficiency can be recovered from the lift induced on the configuration by the pressure field of the nacelle. It is shown, on the basis of linearised theory, that (neglecting the interference between the nacelle and the wing thickness distribution and in the best case where base drag is avoided without boat-tailing the nacelle) the induced lift can only compensate for the increase in drag in cases in which the drag of the original configuration is higher than that of an unwarped wing or the excess cross-sectional area of the nacelle is small.