Some notes on seeking new methods of sailplane lift-drag-curve measurnig

Abstract

With the improvement of sailplane performance the importance of flight measuring continues to increase but simultaneously  difficulties in the accuracy and duration of testing become greater. If the 'classical' method (i.e. measurning the rate-of-sink and air-speed in steady flight) is used, both these factors depend mostly on the meteorological conditions and their influence is increasing the higher the performance attained by the sailplane being tested. While seeking new and better methods, preliminary theoretical analysis and useful practical testing of two methods was carried out.  One was the 'deceleration method' by which the lift-drag curve has been estimated from dynamic pressure-time variation recorded during as exactly held horizontal flattening-out and a somewhat modified 'towed flight method'. It was intended to assess roughly with the most necessary means being disposal the possibilities of using these methods practically.