Report presenting an investigation of the closed wind-tunnel phenomenon of choking and the wall-constriction effects in the subsonic Mach number range where supersonic Mach numbers appear using the hydraulic analogy. Application of the results to wind tunnel testing, the subsonic choking phenomena, and effects of the walls are described.

"Methods are presented that use general correlative time-response input and output data for a linear system to determine the frequency-response function of that system. These methods give an exact description of any linear system for which such transient data are available. Examples are shown of application of a method to both an underdamped and a critically damped exact second-order system, and to an exact first-order system with and without dead time. Experimental data for a turbine-propeller engine showing the response of engine speed to change in propeller-blade angle are presented and analyzed" (p. 547).

Report presenting information about airfoil section normal-force, drag, pitching-moment, flap-normal-force, and hinge-moment characteristics at Mach numbers from 0.5 to 1.0 on an NACA 64A006 airfoil with 15-percent-chord leading-edge flap. Differing results were noted in the Mach ranges of 0.5 to 0.8 and over 0.8.