The energy dependence of film blackening is discussed and shown graphically. The exposure range of films is discussed, and blackening is plotted vs exposure for DuPont No. 502, and for the less sensitive DuPont No. 351. A plan is then described for monitoring radiation exposure to workers by requiring the worker to carry an x-ray film of dental packet size in a badge designed for the purpose. (LEW)

The test of March 7, 1947 was planned as a check on power coefficient values; however, an analysis of reactivity data gave evidence of a considerable flattening of ``A`` rod in the region between 0--75 inches out. A second test of longer duration was therefore made on April 1, 1947 in order to obtain a check calibration of this portion of the control rod. The results of this test verified the flattening of this portion of ``A`` rod. The redetermined power coefficients based on new rod calibrations are given.

Report presenting flight measurements of the pressures on the horizontal tail surfaces of a typical propeller-driven pursuit airplane during stalled pull-outs at high Mach number. Unit loads measured on the stabilizer at safe maneuvering limits were not only considerably in excess of the design unit loads, but also occurred in a direction opposite to the design loads. Revision of the tail-load design requirements and manner of specifying safe maneuverability limits to pilots appears necessary.

Report presenting an investigation of aileron flutter associated with high-speed flight. When the aileron control system was modified by installing a hydraulic irreversible unit, it was possible to delay aileron flutter and reduce its amplitude. Results regarding the aileron flutter with and without the modifications, analysis of the time histories for the control systems, and relation between aileron upfloat and flutter are provided.

Report presenting the results of pressure-distribution tests to determine the effects of compressibility on the characteristics of the NACA 66,2-215, 66,2-015, 65(216)-418, 16-212, and 23015 airfoil sections. Schileren photographs of the air flow and data on the wake characteristics was also obtained.

Memorandum presenting an investigation of two annular diffusers of different conical angles of expansion but constant outer diameters with rotating flow behind a fan. The performance characteristics are determined and the rotational-kinetic-energy effects on the overall energy transformation are observed over a range of inlet mach numbers from 0.1 to 0.44 and angles of flow up to 28 degrees.

The results of an investigation of two 10-foot-diameter, two-blade NACA propellers are presented for a range of blade angles from 20 degrees to 55 degrees at airspeeds up to 500 miles per hour. These results are compared with those from previous investigations of five related NACA propellers in order to evaluate the effects of blade-section thickness ratios on propeller aerodynamic characteristics.

"A general algebraic method of attack on the problem of controlling gas-turbine engines having any number of independent variables was utilized employing operational functions to describe the assumed linear characteristics for the engine, the control, and the other units in the system. Matrices were used to describe the various units of the system, to form a combined system showing all effects, and to form a single condensed matrix showing the principal effects. This method directly led to the conditions on the control system for noninteraction so that any setting disturbance would affect only its corresponding controlled variable" (p. 581).

"Investigations were conducted in the Cleveland altitude wind tunnel to determine the performance and operational characteristics of the 19B-2, 19B-8, and 19XS-1 turbojet engines. One objective was to determine the effect of altitude, flight Mach number, and tail-pipe-nozzle area on the performance characteristics of the six-stage and ten-stage axial-flow compressors of the 19B-8 and 19XB-1 engines, respectively, The data were obtained over a range of simulated altitudes and flight Mach numbers" (p. 1).