The effects of mass distribution on lateral stability and control characteristics of an airplane have been determined by flight tests of a model in the NACA free-flight tunnel. In the investigation, the rolling and yawing moments of inertia were increased from normal values to values up to five times normal. For each moment-of-inertia condition, combinations of dihedral and vertical-tail area representing a variety of airplane configurations were tested. The results of the flight tests of the model were correlated with calculated stability and control characteristics and, in general, good agreement was obtained.

"Results of flight tests of the performance and cooling characteristics of three NACA D cowlings and of a conventional NACA D cowling on the XP-42 airplane are summarized and compared. The D cowling is, in general, characterized by the use of an annular inlet and diffuser section for the engine-cooling air. The D cowlings tested were a long-nose high-inlet-velocity cowling, a short-nose high-inlet-velocity cowling, and a short-nose low inlet-velocity cowling" (p. 371).

This report was written to replace the directions submitted on April 12, 1943 with improved directions for the preparation of chemical solution X(OC₂H₅)₅.

Technical report: The apparatus for the low pressure combustion method of determining carbon in iron and steel has be redesigned to increase the speed of manipulation. It has been tested by running several thousand determinations and found to yield results in good agreement with Wooten's form of the apparatus. A detailed description of the equipment and its manipulation is given together with an account of experimental studies on the method. Results are also shown for the carbon content of copper.