ESDU 89009 provides a prediction method for full-span and part-span sealed controls that can also be used for elevators and rudders. Data for two-dimensional flow, assumed constant over the span of the control, are corrected for induced angle of attack and induced camber on the basis of lifting-surface theory, and Prandtl-Glauert similarity laws are used to correct for compressibility. The part-span correction for controls extending spanwise from any station to near the tip is empirical. Sketches compare predictions by the method with experimental data extracted from the literature and show the derivative with incidence to be estimated within 0.07 per radian and with control deflection within 0.05 per radian. The range of geometries used in developing the method included wing aspect ratios of 2 to 8, half chord sweeps up to 50 degrees and thickness/chord ratio of 0.06 to 0.14. The two-dimensional data, including if required the effect of either nose or Irving internal balance, are available in other ESDU documents in the Series. A worked example illustrates the use of the method.