Abstract:

ESDU 79006 gives a correlation of experimental data drawn from a wide range of sources in the literature. Values of N_v for a yawing axis at mid-body position are predicted by an empirical equation in terms of body side area and a parameter that allows for different fore- and after-body shapes. An equation for Y_v is also given involving empirical factors shown graphically, one depending on body geometry and wing height, and one depending on wing geometry; the value of Y_v can then be used to convert N_v to a different yawing axis position. The method is developed using data at low incidence for small wing sweeps; the effects of incidence, and sweep and dihedral angle, are discussed. . For the effect of nacelles only a few data were available for models tested both with and without free flow nacelles. Rear-fuselage mounted nacelles affect only the contribution due to fin and tailplane (see ESDU 82010) and it is not possible to derive a generalised method for estimating their effect on the derivatives. For two underwing nacelles/pylons a method is given for predicting their contribution to Y_v as a function of the width of the nacelle and its distance below the wing, and hence the contribution to N_v which is additionally a function of the position of the inlet plane and nacelle internal diameter. Configurations with four nacelles are treated by summing the effects of two pairs. ESDU 82011 gives a comprehensive example showing the prediction of those derivatives for a complete aircraft using ESDU data. ESDU 79006 contains worked examples to illustrate the prediction of the contributions of wing, fuselage and nacelles.