INTRODUCTION Data sheets in the group RJ2 contain analytical methods for the reduction of flight test results on turbo-jet aircraft to standard atmospheric conditions and for corrections for weight and rpm changes. Except for take-off and landing@ the method given in Item Nos 70020 to 70023 is the most suitable for turbo-jets@ provided that a sufficient number of experimental points can be obtained. In some cases@ however@ the reduction of isolated points is required and this must be done by analytical methods. In the case of take-off and landing@ graphical methods are unsatisfactory and an analytical method is always used. The formulae given apply only for small differences in the various parameters@ and therefore when the corrections applied are large it may be necessary to divide the process into steps.