ESDU 96026 provides an empirical method applying to a spoiler on one wing panel. The drag increment is considered as the sum of a profile drag component and an induced drag component which includes the effect of deploying a trailing-edge flap. The increment in yawing moment arises from the direct moment associated with the drag increment but includes an indirect effect due to the sidewash at the tail unit caused by the spoiler flow field. Comparisons are shown of the predicted results against experimental data. A worked example illustrates the use of the method.