Research Reports and Memoranda

The measurement of small deflections, the most important duty of measurement technics in aeronautical research, may be executed very simply and rapidly by a scratch record of the motions—in as far as possible in natural size— on a suitable inscribing surface, the record being subsequently analysed under the microscope or lens or by microphotographic means. A whole series of measuring instruments of the scratch recording type have been evolved to serve the most diverse purposes in aeronautical research. These are described in this report, the degree of accuracy obtainable in each case being examined.