ESDU 71004 gives data for the calculation of the elastic stresses in the flanges of curved beams subjected to bending in the plane of curvature. The data are provided in the form of flange efficiency factors from which equivalent flanges may be obtained for use with beam theory. The data are based on the behaviour of a complete ring subjected to pure bending. They may be applied to other curved beams and in most such cases will tend to overestimate the resulting stresses and deflections. Common cross-sections are covered specifically and analytical expressions are given for use with other cross-sections.