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  • 1
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    Adaptation of a modern medium helicopter (Sikorsky S-76) to higher harmonic control (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Sikorsky Aircraft has performed analytical studies, design analyses, and risk reduction tests have been performed for Higher Harmonic Control (HHC) on the S-76. The S-76 is an 8 to 10,000 lb helicopter which cruises at 145 kts. Flight test hardware has been assembled, main servo frequency response tested and upgraded, aircraft control system shake tested and verified, open loop controllers designed and fabricated, closed loop controllers defined and evaluated, and rotors turning ground and flight tests planned for the near future. Open loop analysis shows that about 2 deg of higher harmonic feathering at the blade 75% radius will be required to eliminate 4P vibration in the cockpit.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA. Ames Research Center Rotorcraft Dynamics 1984; p 365-378
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Analysis of potential helicopter vibration reduction concepts (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results of analytical investigations to develop, understand, and evaluate potential helicopter vibration reduction concepts are presented in the following areas: identification of the fundamental sources of vibratory loads, blade design for low vibration, application of design optimization techniques, active higher harmonic control, blade appended aeromechanical devices, and the prediction of vibratory airloads. Primary sources of vibration are identified for a selected four-bladed articulated rotor operating in high speed level flight. The application of analytical design procedures and optimization techniques are shown to have the potential for establishing reduced vibration blade designs through variations in blade mass and stiffness distributions, and chordwise center-of-gravity location.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA. Ames Research Center Rotorcraft Dynamics 1984; p 343-363
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Exploratory wind-tunnel investigation of the stability and control characteristics of advanced general aviation configurations (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results of low-speed wind-tunnel investigations are presented for two general aviation configurations: the AVTEK canard configuration and the DeVore conventional configuration. Cooperative research programs were undertaken by industry and NASA to jointly conduct tests in the NASA Langley 12-Foot Low-Speed Wind Tunnel to explore stability and control characteristics of each configuration. A 1/5-scale AVTEK model and a 1/6-scale DeVore model were tested over an angle-of-attack range of up to 45 deg and an angle-of-sideslip range of up to 20 deg. Results from the AVTEK test are presented with an emphasis on the effects of configuration on the stall and poststall characteristics. Results from the DeVore test are presented with emphasis on the effects of wing leading-edge droop design on spin resistance characteristics.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 86-2596
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Preliminary control law and hardware designs for a ride quality augmentation system for commuter aircraft. Phase 2 (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The continued investigation of the design of Ride Quality Augmentation Systems (RQAS) for commuter aircraft is described. The purpose of these RQAS is the reduction of the vertical and lateral acceleration response of the aircraft due to atmospheric turbulence by the application of active control. The current investigations include the refinement of the sample data feedback control laws based on the control-rate-weighting and output-weighting optimal control design techniqes. These control designs were evaluated using aircraft time simulations driven by Dryden spectra turbulence. Fixed gain controllers were tested throughout the aircrft operating envelope. The preliminary design of the hardware modifications necessary to implement and test the RQAS on a commuter aircraft is included. These include a separate surface elevator and the flap modifications to provide both direct lift and roll control. A preliminary failure mode investigation was made for the proposed configuration. The results indicate that vertical acceleration reductions of 45% and lateral reductions of more than 50% are possible. A fixed gain controller appears to be feasible with only minor response degradation.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-CR-4014 , NAS 1.26:4014 , KU-FRL-6132-2
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Ultrareliable, fault-tolerant control systems: A conceptual description (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An Ultrareliable, Fault-Tolerant, Control-System (UFTCS) concept is described using a systems design philosophy which allows development of system structures containing virtually no common elements. Common elements limit achievable system reliability and can cause catastrophic loss of fault-tolerant system function. The UFTCS concept provides the means for removing common system elements by permitting the elements of the system to operate as independent, uncoupled entities. Multiple versions of the application program are run on dissimilar hardware. Fault tolerance is achieved through the use of static redundancy management.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TM-86017 , A-9876 , NAS 1.15:86017
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Demonstration of relaxed static stability on a commercial transport (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The application of relaxed static stability was studied under a program to determine ways of improving the energy efficiency in current and future transport aircraft. Pitch active control systems (PACs) were developed for application in the near term to current aircraft and in the next generation to advanced aircrft of the future. Analyses identified potential drag benefits of: (1) 2% for current transport aircraft with neutral stability; and (2) as much as 17% for next generation aircraft with high aspect ratio supercritical wings which must operate 10 to 15% statistically unstable to achieve optimum performance. Flight test evaluations of the near-term PACs were conducted to a 3% mean aerodynamic chord (MAC) negative static margin on a Lockheed L-1011 aircraft. The advanced PACs was demonstrated to a 20% MAC negative static margin on a piloted visual motion simulator at the NASA Langley Research Center. Test results for both systems showed flying qualities characteristics as good as current conventional aircraft.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AGARD Active Control Systems: Rev., Evaluation and Projections; 18 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Development and flight test of a helicopter, X-band, portable precision landing system concept (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A beacon landing system (BLS) is being developed and flight tested as a part of NASA's Rotorcraft All-Weather Operations Research Program. The system is based on state-of-of-the-art X-band radar technology and digital processing techniques. The bLS airborne hardware consists of an X-band receiver and a small micropreocessor, installed in conjunction wht the aircraft instrument landing system (ILS) receiver. The microprocessor analyzes the X-band, BLS pulses and outputs ILS-compatible localizer and glide slope signals. Range information is obtained using an on-board weather/mapping radar in conjunction with the BLS. The ground station is an inexpensive, portable unit; it weighs less than 70 lb and can be quickly deployed at a landing site. Results from the flight-test program show that the BLS has a significant potential for providing rotorcaraft with low-cost, precision instrument approach capability in remote areas.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TM-86710 , NAS 1.15:86710
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Handling qualities of a wide-body transport airplane utilizing Pitch Active Control Systems (PACS) for relaxed static stability application (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Piloted simulation studies have been conducted to evaluate the effectiveness of two pitch active control systems (PACS) on the flying qualities of a wide-body transport airplane when operating at negative static margins. These two pitch active control systems consisted of a simple 'near-term' PACS and a more complex 'advanced' PACS. Eight different flight conditions, representing the entire flight envelope, were evaluated with emphasis on the cruise flight conditions. These studies were made utilizing the Langley Visual/Motion Simulator (VMS) which has six degrees of freedom. The simulation tests indicated that (1) the flying qualities of the baseline aircraft (PACS off) for the cruise and other high-speed flight conditions were unacceptable at center-of-gravity positions aft of the neutral static stability point; (2) within the linear static stability flight envelope, the near-term PACS provided acceptable flying qualities for static stabilty margins to -3 percent; and (3) with the advanced PACS operative, the flying qualities were demonstrated to be good (satisfactory to very acceptable) for static stabilty margins to -20 percent.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TP-2482 , L-15928 , NAS 1.60:2482
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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