IHS ESDU Lift and drag of two staggered lifting surfaces at low speeds. 81023

ESDU 81023 provides a means of estimating the effect on lift and drag of the variation in geometry and disposition, with respect to each other and to the centre of gravity, of a combination of two straight-tapered lifting surfaces trimmed in pitch and having a given margin of static stability. It involves considerable simplification but provides a practical method suitable for application in the early stages of an aircraft design project or for incorporation into a multi-variate analysis program. It requires the evaluation of downwash gradient, however, which is a relatively complex calculation, and its use is in assessing the effect of changing the geometry, so a Fortran program of the method is provided as ESDUpac A8123. Details of the input and output are illustrated by four worked examples, two of which use similar input data to those used to demonstrate the hand calculation procedure.