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Theoretical Investigation of the Effects of the Artificial-Feel System on the Maneuvering Characteristics of the F-89 Airplane

Description: The possibility of overshooting the anticipated normal acceleration as a result of the artificial-feel characteristics of the F-89C airplane at a condition of minimum static stability was investigated analytically by means of an electronic simulator. Several methods of improving the stick-force characteristics were studied. It is shown that, due to the lag in build-up of the portion of the stick force introduced by the bobweight, it would be possible for excessive overshoots of normal acceleration to occur in abrupt maneuvers with reasonable assumed control movements. The addition of a transient stick force proportional to pitching acceleration (which leads the normal acceleration) to prevent this occurring would not be practical due to the introduction of an oscillatory mode to the stick-position response. A device to introduce a viscous damping force would Improve the stick-force characteristics so that normal acceleration overshoots would not be likely, and the variation of the maximum stick force in rapid pulse-type maneuvers with duration of the maneuver then would have a favorable trend.
Date: December 31, 1952
Creator: Abramovitz, Marvin; Schmidt, Stanley F. & Belsley, Steven E.

Effects of inlet icing on performance of axial-flow turbojet engine in natural icing conditions

Description: A flight investigation in natural icing conditions was conducted to determine the effect of inlet ice formations on the performance of axial-flow turbojet engines. The results are presented for icing conditions ranging from a liquid-water content of 0.1 to 0.9 gram per cubic meter and water-droplet size from 10 to 27 microns at ambient-air temperature from 13 to 26 degrees F. The data show time histories of jet thrust, air flow, tail-pipe temperature, compressor efficiency, and icing parameters for each icing encounter. The effect of inlet-guide-vane icing was isolated and shown to account for approximately one-half the total reduction in performance caused by inlet icing.
Date: May 25, 1950
Creator: Acker, Loren W & Kleinknecht, Kenneth S

Investigations on wings with and without sweepback at high subsonic speeds

Description: Drag tests at zero lift have been made at Mach numbers from 0.7 to approximately 0.95 in the high speed wind tunnel of the Institute of Aerodynamics, ETH, Zurich, on a group of untapered wings of aspect ratio 3.25, having sweep angles of 0 degree and 35 degrees. For each sweep angle, a series of geometrically similar models was tested at a constant Reynolds number to provide a verification of computed tunnel blocking corrections. Tests were also made for wings having thickness ratios of 0.09 and 0.12 and the results compared with results predicted by von Karman's similarity law.
Date: November 1, 1951
Creator: Ackeret, Jakob; Rott, Nikolaus & Degen, Max

Theoretical damping in roll and rolling moment due to differential wing incidence for slender cruciform wings and wing-body combinations

Description: A method of analysis based on slender-wing theory is developed to investigate the characteristics in roll of slender cruciform wings and wing-body combinations. The method makes use of the conformal mapping processes of classical hydrodynamics which transform the region outside a circle and the region outside an arbitrary arrangement of line segments intersecting at the origin. The method of analysis may be utilized to solve other slender cruciform wing-body problems involving arbitrarily assigned boundary conditions. (author).
Date: January 1, 1952
Creator: Adams, Gaynor J & DUGAN DUANE W

Determination of Shapes of Boattail Bodies of Revolution for Minimum Wave Drag

Description: By use of an approximate equation for the wave drag of slender bodies of revolution in a supersonic flow field, the optimum shapes of certain boattail bodies are determined for minimum wave drag. The properties of three specific families of bodies are determined, the first family consisting of bodies having a given length and base area and a contour passing through a prescribed point between the nose and base, the second family having fixed length, base area, and maximum area, and the third family having given length, volume, and base area. The method presented is easily generalized to determine minimum-wave-drag profile shapes which have contours that must pass through any prescribed number of points. According to linearized theory, the optimum profiles are found to have infinite slope at the nose but zero radius of curvature so that the bodies appear to have pointed noses, a zero slope at the body base, and no variation of wave drag with Mach number. For those bodies having a specified intermediate.diameter (that is, location and magnitude given), the maximum body diameter is shown to be larger, in general, than the specified diameter. It is also shown that, for bodies having a specified maximum diameter, the location of the maximum diameter is not arbitrary but is determined from the ratio of base diameter to maximum diameter.
Date: November 1, 1951
Creator: Adams, Mac C.

Investigation of Downwash, Sidewash, and Mach Number Distribution behind a Rectangular Wing at a Mach Number of 2.41

Description: An investigation of the nature of the flow field behind a rectangular circular-arc wing has been conducted in the Langley 9-inch supersonic tunnel. Pitot- and static-pressure surveys covering a region of flow behind the wing have been made together with detailed pitot surveys throughout the region of the wake. In addition, the flow direction has been measured using a weathercocking vane measurements. Theoretical calculations of the variation of both downwash and sidewash with angle of attack using Lagerstrom's superposition method have been made. In addition the effect of the wing thickness on the sidewash with the wing at 0 angle of attack has been evaluated. Near an angle of attack of 0, agreement between theory and experiment is good, particularly for the downwash results, except in the plane of the wing, inboard of the tip. In this region the proximity of the shed vortex sheet and the departure of the spanwise distribution of vorticity from theory would account for the disagreement. At higher angles of attack prediction of downwash depends on a knowledge of the location of the trailing vortex sheet, in order that the downwash may be corrected for its displacement and distortion. The theoretical location of the trailing vortex sheet, based on the theoretical downwash values integrated downstream from the wing trailing edge, is shown to differ widely from the experimental case. The rolling-up of the trailing vortex sheet behind the wing tip is evidenced by both the wake surveys and the flow-angle measurements.
Date: September 14, 1950
Creator: Adamson, D. & Boatright, William B.

Investigation of downwash, sidewash, and Mach number distribution behind a rectangular wing at a Mach number of 2.41

Description: An investigation of the nature of the flow field behind a rectangular wing of circular arc cross section has been conducted in the Langley 9-inch supersonic tunnel. Pitot- and static-pressure surveys covering a region of flow behind the wing have been made together with detailed pitot surveys throughout the region of the wake. In addition, the flow direction has been measured by means of a weathercocking vane. Theoretical calculations have been made to obtain the variation of both downwash and sidewash with angle of attack by using the superposition method of Lagerstrom, Graham, and Grosslight. In addition, the effect of wing thickness on the sidewash with the wing at 0 degree angle of attack has been evaluated.
Date: January 1, 1957
Creator: Adamson, David & Boatright, William B

Analysis of the horizontal-tail loads measured in flight on a multiengine jet bomber

Description: From Introduction: "The primary objectives of the present paper are to report the horizontal-tail-loads measurements for configuration B which have not previously been reported and to summarize the horizontal-tail-loads results obtained with both configurations. The manner in which the aerodynamic-loads data were analyzed to include structural temperature effects and fuselage flexibility effects constitutes an important part of the present paper. "
Date: September 1955
Creator: Aiken, William S & Wiener, Bernard

Analysis of horizontal-tail loads in pitching maneuvers on a flexible swept-wing jet bomber

Description: From Introduction: "The analysis of flight data in the present report is, to a large extent, based on analyses and information contained in references 1 and 2 for wing deflections, reference 3 for horizontal-tail parameters, reference 4 for airplane lift-curve slopes and angles of zero lift, and reference 5 for wing centers of pressure."
Date: December 1957
Creator: Aiken, William S , Jr

Strain-Gage Measurements of Buffeting Loads on a Jet-Powered Bomber Airplane

Description: Buffet boundaries, buffeting-load increments for the stabilizers and elevators, and buffeting bending-moment increments for the stabilizers and wings as measured in gradual maneuvers for a jet-powered bomber airplane are presented. The buffeting-load increments were determined from strain-gage measurements at the roots or hinge supports of the various surfaces considered. The Mach numbers of the tests ranged from 0.19 to 0.78 at altitudes close to 30,000 feet. The predominant buffet frequencies were close to the natural frequencies of the structural components. The buffeting-load data, when extrapolated to low-altitude conditions, indicated loads on the elevators and stabilizers near the design limit loads. When the airplane was held in buffeting, the load increments were larger than when recovery was made immediately.
Date: March 19, 1951
Creator: Aiken, William S., Jr. & See, John A.