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  • 1
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    Extension of the Rh I-Like Isoelectronic Sequence to the Spectrum of Ag III (1935)
    American Physical Society
    Details
    Publication Date: 1935-08-15
    Print ISSN: 0031-899X
    Electronic ISSN: 1536-6065
    Topics: Physics
    Published by American Physical Society
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    PAPER CURRENT
  • 2
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    Some Higher Terms in the Spectrum of Ag II (1935)
    American Physical Society
    Details
    Publication Date: 1935-06-01
    Print ISSN: 0031-899X
    Electronic ISSN: 1536-6065
    Topics: Physics
    Published by American Physical Society
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    PAPER CURRENT
  • 3
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    Control considerations for CCV fighters at high angles of attack (1979)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Wind tunnel and piloted simulation studies were conducted to investigate the potential high angle of attack control problems that are introduced by the use of the CCV concept of relaxed static pitch stability (RSS) on fighter aircraft. A conventional wing/aft tail design incorporating modest levels of static instability and a close-coupled canard/wing design exhibiting very high levels of instability was investigated. Two types of high angle of attack control problems can result from the use of RSS: pitch departures caused by coupling and deep stall trim. Avoidance of these problems requires that the airplane have sufficient nose-down pitch control at high angles of attack. The effectiveness of several pitch control configurations were investigated including conventional aft-mounted stabilators, wing-mounted elevators, canard-mounted flaps, and all-moveable canards. Varying the incidence of the canards was the most effective scheme; however, very large deflections may be required on highly unstable configurations to prevent pitch departure without sacrificing roll performance and to avoid deep stall trim. For situations where the high angle of attack pitch control requirement is not met, control laws were developed to inhibit the departure and to allow deep stall recovery. However, these schemes involve limiting airplane roll capability and therefore can potentially compromise maneuverability.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AGARD Aerodyn. Characteristics of Controls; 10 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Use of piloted simulation for studies of fighter departure/spin susceptibility (1978)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The NASA-Langley Research Center has incorporated into its stall/spin research program on military airplanes the use of piloted, fixed-base simulation to complement the existing matrix of unique research testing techniques. The piloted simulations of fighter stall/departure flight dynamics are conducted on the Langley Differential Maneuvering Simulator (DMS). The objectives of the simulation research are reviewed. The rationale underlying the simulation methods and procedures used in the evaluation of airplane characteristics is presented. The evaluation steps used to assess fighter stall/departure characteristics are discussed. Simulation results are presented to illustrate the flight dynamics phenomena dealt with. The considerable experience accumulated in the conduct of piloted stall/departure simulation indicates that simulation provides a realistic evaluation of an airplane's maneuverability at high angles of attack and an assessment of the departure and spin susceptibility of the airplane. This realism is obtained by providing the pilot a complete simulation of the airplane and control system which can be flown using a realistic cockpit and visual display in simulations of demanding air combat maneuvering tasks. The use of the piloted simulation methods and procedures described were found very effective in identifying stability and control problem areas and in developing automatic control concepts to alleviate many of these problems. A good level of correlation between simulated flight dynamics and flight test results were obtained over the many fighter configurations studied in the simulator.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AGARD Piloted Aircraft Environ. Simulation Tech.; 13 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Results of recent NASA studies on spin resistance (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Some of the factors which contribute to good stall/spin characteristics of a current fighter configuration indicate that the design of airframe components for inherent spin resistance is very configuration dependent and that few generalizations can be made. Secondary design features, such as fuselage forebody shape, can have significant effects on stability characteristics at high angles of attack. Recent piloted simulator studies and airplane flight tests have indicated that current automatic control systems can be tailored so as to provide a high degree of spin resistance for some configurations without restrictions to maneuverability. Such systems result in greatly increased pilot confidence and increased tactical effectiveness.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AGARD Stall(Spin Probl. of Mil. Aircraft; 12 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Experimental investigation of forebody and wing leading-edge vortex interactions at high angles of attack (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted to assess the vortex flow-field interactions on an advanced, twin-jet fighter aircraft configuration at high angles of attack. Flow-field surveys were conducted on a small-scale model in the Northrop 0.41 - by 0.60-meter water tunnel and, where appropriate, the qualitative observations were correlated with low-speed wind tunnel data trends obtained on a large-scale model of the advanced fighter in the NASA Langley Research Center 30- by 60-foot (9.1- by 18.3-meter) facility. Emphasis was placed on understanding the interactions of the forebody and LEX-wing vortical flows, defining the effects on rolling moment variation with sideslip, and identifying modifications to control or regulate the vortex interactions at high angles of attack. The water tunnel flow visualization results and wind tunnel data trend analysis revealed the potential for strong interactions between the forebody and LEX vortices at high angles of attack. In particular, the forebody flow development near the nose could be controlled by means of carefully-positioned radome strakes. The resultant strake-induced flow-field changes were amplified downstream by the more powerful LEX vortical motions with subsequent large effects on wing flow separation characteristics.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Vortical Type Flows in Three Dimensions; 20 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Control-system techniques for improved departure/spin resistance for fighter aircraft (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Some fundamental information on control system effects on controllability of highly maneuverable aircraft at high angles of attack are summarized as well as techniques for enhancing fighter aircraft departure/spin resistance using control system design. The discussion includes: (1) a brief review of pertinent high angle of attack phenomena including aerodynamics, inertia coupling, and kinematic coupling; (2) effects of conventional stability augmentation systems at high angles of attack; (3) high angle of attack control system concepts designed to enhance departure/spin resistance; and (4) the outlook for applications of these concepts to future fighters, particularly those designs which incorporate relaxed static stability.
    Keywords: AERONAUTICS (GENERAL)
    Type: NASA-TP-1689 , L-13453
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Simulator study of stall/post-stall characteristics of a fighter airplane with relaxed longitudinal static stability (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A real-time piloted simulation was conducted to evaluate the high-angle-of-attack characteristics of a fighter configuration based on wind-tunnel testing of the F-16, with particular emphasis on the effects of various levels of relaxed longitudinal static stability. The aerodynamic data used in the simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative low-speed combat maneuvering. Results of the investigation show that the airplane with the basic control system was resistant to the classical yaw departure; however, it was susceptible to pitch departures induced by inertia coupling during rapid, large-amplitude rolls at low airspeed. The airplane also exhibited a deep-stall trim which could be flown into and from which it was difficult to recover. Control-system modifications were developed which greatly decreased the airplane susceptibility to the inertia-coupling departure and which provided a reliable means for recovering from the deep stall.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TP-1538 , L-12854
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Effects of fuselage forebody geometry on low-speed lateral-directional characteristics of twin-tail fighter model at high angles of attack (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Low-speed, static wind-tunnel tests were conducted to explore the effects of fighter fuselage forebody geometry on lateral-directional characteristics at high angles of attack and to provide data for general design procedures. Effects of eight different forebody configurations and several add-on devices (e.g., nose strakes, boundary-layer trip wires, and nose booms) were investigated. Tests showed that forebody design features such as fineness ratio, cross-sectional shape, and add-on devices can have a significant influence on both lateral-directional and longitudinal aerodynamic stability. Several of the forebodies produced both lateral-directional symmetry and strong favorable changes in lateral-directional stability. However, the same results also indicated that such forebody designs can produce significant reductions in longitudinal stability near maximum lift and can significantly change the influence of other configuration variables. The addition of devices to highly tailored forebody designs also can significantly degrade the stability improvements provided by the clean forebody.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1592 , L-13270
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Low-speed stability and control wind-tunnel investigations of effects of spanwise blowing on fighter flight characteristics at high angles of attack (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effects of spanwise blowing on two configurations representative of current fighter airplanes were investigated. The two configurations differed only in wing planform, with one incorporating a trapezoidal wing and the other a 60 delta wing. Emphasis was on determining the lateral-directional characteristics, particularly in the stall/departure angle-of-attack range; however, the effects of spanwise blowing on the longitudinal aerodynamics were also determined. The-tunnel tests included measurement of static force and forced-oscillation aerodynamic data, visualization of the airflow changes created by the spanwise blowing, and free-flight model tests. The effects of blowing rate, chordwise location of the blowing ports, asymmetric blowing, and blowing on the conventional aerodynamic control characteristics were investigated. In the angle-of-attack regions in which the spanwise blowing substantially improved the wing upper-surface flow field (i.e., provided reattachment of the flow aft of the leading-edge vortex), improvements in both static and dynamic lateral-directional stability were observed. Blowing effects on stability could be proverse or adverse depending on blowing rate, blowing port loaction, and wing planform. Free-flight model tests of the trapezoidal wing confirmed the beneficial effects of spanwise blowing measured in the static and dynamic force tests.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2431 , L-15851 , NAS 1.60:2431
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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