This compilation of the outstanding characteristics of the available aircraft engines of the world was prepared as a compact ready reference for desk use. It does not pretend to be anything but a skeleton outline of the characteristics of engines reported in the technical press as being in either the experimental, development, or production stage. At present progress is quite rapid and by the time this compilation is disseminated new models may have superseded those listed, or changes may have been made which will entirely change the characteristics given" (p. 1).