ALBERT

Description: The hydrodynamic characteristics of a 1/10-size powered dynamic model of the XP5Y-1 flying boat were determined in Langley tank no. 1. Stable take-offs were possible at all practicable positions of the center of gravity and flap deflections. An increase in gross load from 123.5 to 150.0 pounds (21.5 percent) had only a slight effect on the stable range for take-off. A decrease in forward acceleration from 3.0 to 1.0 feet per second per second had only a very small effect on the stable range for take-off. In general, the landings were free from skipping except at trims below 6 deg where one skip was encountered at an aft position of the center of gravity. The model porpoised during the landing runout at all positions of the center of gravity when landed at trims above 10 deg. Spray in the propellers was light at the design gross load, and was not considered excessive,at a gross load of 136.0 pounds.

Description: Measurements were made, in dives to transonic speeds, of the static-pressure position error at a distance of one chord ahead of the McDonnell XF-88 airplane. The airplane incorporates a wing which is swept back 35 deg along the 0.22 chord line and utilizes a 65-series airfoil with a 9-percent-thick section perpendicular to the 0.25-chord line. The section in the stream direction is approximately 8-percent thick. Data up to a Mach number of about 0.97 were obtained within an airplane normal-force-coefficient range from about 0.05 to about 0.68. Data at Mach numbers above about 0.97 were obtained within an airplane normal-force-coefficient range from about 0.05 to about 0.68. Results of the measurements indicate that the static-pressure error, within the accuracy of measurement, is negligible from a Mach number of 0.65 to a Mach number of about 0.97. With a further increase in Mach number, the static-pressure error increases rapidly; at the highest Mach number attained in these tests (about M = 1.038), the error increases to about 8 percent of the impact pressure. Above a Mach number of about 0.975, the recorded Mach number remains substantially constant with increasing true Mach number; the installation is of no value between a Mach number of about 0.975 and at least 1.038, as the true Mach number cannot be obtained from the recorded Mach number in this range. Previously published data have shown that at 0.96 chord ahead of the wing tip of the straight-wing X-l airplanes, a rapid rise of position error started at a Mach number of about 0.8. In the case of the XF-88 airplane, this rise of position error was delayed, presumably by the sweep of the wing, to a Mach number of about 0.97.

Description: This report presents the results of an investigation in the transonic speed range of the longitudinal stability characteristics of a proposed configuration for the Republic XF-91 airplane. The tests covered a Mach number range of 0.55 to 1.05 and a Reynolds number range from 400,000 to 1,375,000. Lift, pitching-moment, and rolling-moment characteristics of the half model and the hinge moments on the all-moving tail were measured. The downwash factor delta x epsilon / delta x alpha at the tail was determined from the pitching-moment data. A calculation of the elevator deflection and stick force required for trim was also made. It was found that the variation of force and moment coefficients was linear through the test angle-of-attack range of -1 deg to 8 deg at any Mach number; that the stability increased markedly at Mach numbers above 0.85; that the effectiveness of the tail in producing pitching moments decreased about one-third with increasing Mach numbers and that the value of the downwash factor, delta x epsilon / delta x alpha, at the tail decreased from about 0.35 at a Mach number of 0.85 to about zero at a Mach number near 0.95 and became slightly negative at higher Mach numbers. The calculated values of stick force per g and elevator deflection per g, assuming no aerodynamic balance, increased rapidly above a Mach number of 0.85.