INTRODUCTION A computer program@ called ESDUpac A8840@ has been written by the Computer Products Group of ESDU International to determine aircraft aileron rolling moment and yawing moment coefficients at subsonic speeds. It is based on the methods of Item Nos 88013 and 88029 (Derivations 1 and 2)@ the graphical data of those Items being held in digitised form. For full details of the methods used Item Nos 88013 and 88029 should be consulted. Table 2.1 lists the input parameters for the program. It gives their program name and their notation in Item Nos 88013 and 88029 (unless they are control variables of integer type in the program). The first three lines of the input are reserved for the user to input text to identify a particular run. Section 4 poses a problem that illustrates the input to and ouput from the program. This includes the worked examples of Item Nos 88013 and 88029 but is more general. Section 4.1 gives the required input file. The output that results is shown in Section 4.2. There is firstly an echo of the input data@ then for each chosen pair of aileron angles the rolling moment coefficient Cl and the yawing moment coefficient Cn are given as functions of CL @ the total lift coefficient@ and DCLf@ the lift coefficient component due to trailing-edge flap deployment. The rolling moment coefficient derivative (per radian)@ for aileron angles measured about the hinge line@ is given separately and for a given configuration is a constant that is independent of aileron setting. Small differences in magnitude between the computer output and the values in the worked examples are due to the approximate curve fitting in the program.