CALIBRATING SAILPLANE PERFORMANCE USING GROUND-BASED DATUM FEATURES, A PROPOSAL

Abstract

The Fairchild Flight Analyzer is a stationary, ground-based camera which records 58 spaced images of a tracked aircraft on a glass slide of 22.8 cm width (9 inches). It has a 15.24 cm (6 inch) Metrogon Reconnaissance lens with a field of view of 93 degrees. One fixed background is recorded. The time of every spaced exposure is shown on each image with an accuracy of one millisecond. For sailplane calibration the background should include features that define the length of the surveyed course above which the glider flies and to provide a true horizontal reference. By using a Mann Comparator to measure the altitude lost as shown on the glass slide and comparing this to the indicated length of the course, the L/D ratio for each constant speed run can be found. The glider's ground speed is found by course length divided by elapsed time. In the glider, a sepalate camela records the airspeed to establish how steadily it indicates during each test run.  By conducting the tests in fair weather, near dawr and using devices to record ambient air movement it should be possible to obtain results which are accurate and which become permanent records.