Testing of Controllable-Pitch Propellers

So much has been written about the effect of controllable propellers on airplane performance that aeronautical engineers now are probably more interested than ever before in the general engineering background of this device which permits them to use wing loadings upward of 20 lb per sq ft. The problem involved in changing the pitch angle of blades subjected to centrifugal loads of the order of 50 tons with safety and reasonable weight limits is obviously one which requires a competent design and testing staff equipped with elaborate facilities. The purpose of this paper is to describe some unique test methods and equipment which have been used successfully both in the development and in the testing of the Lycoming-Smith propeller.