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  • 1
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    High angle-of-attack flush airdata sensing system (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: Journal of Aircraft (ISSN 0021-8669); 29; 5, Se; 915-919
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Development of a pneumatic high-angle-of-attack Flush Airdata Sensing (HI-FADS) system (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The HI-FADS system design is an evolution of the FADS systems (e.g., Larson et al., 1980, 1987), which emphasizes the entire airdata system development. This paper describes the HI-FADS measurement system, with particular consideration given to the basic measurement hardware and the development of the HI-FADS aerodynamic model and the basic nonlinear regression algorithm. Algorithm initialization techniques are developed, and potential algorithm divergence problems are discussed. Data derived from HI-FADS flight tests are used to demonstrate the system accuracies and to illustrate the developed concepts and methods.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: In: Control and dynamic systems. Vol. 52 - Integrated technology methods and applications in aerospace systems design (A94-12611 02-01); p. 453-511.
    Format: text
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  • 3
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    In-flight demonstration of a Real-Time Flush Airdata Sensing (RT-FADS) system (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A prototype real-time flush airdata sensing (RT-FADS) system has been developed and flight tested at the NASA Dryden Flight Research Center. This system uses a matrix of pressure orifices on the vehicle nose to estimate airdata parameters in real time using nonlinear regression. The algorithm is robust to sensor failures and noise in the measured pressures. The RT-FADS system has been calibrated using inertial trajectory measurements that were bootstrapped for atmospheric conditions using meteorological data. Mach numbers as high as 1.6 and angles of attack greater than 45 deg have been tested. The system performance has been evaluated by comparing the RT-FADS to the ship system airdata computer measurements to give a quantitative evaluation relative to an accepted measurement standard. Nominal agreements of approximately 0.003 in Mach number and 0.20 deg in angle of attack and angle of sideslip have been achieved.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: NASA-TM-104314 , H-2053 , NAS 1.15:104314
    Format: application/pdf
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  • 4
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    Development of a pneumatic high-angle-of-attack flush airdata sensing system (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A nonintrusive high-angle-of-attack flush airdata sensing system was installed and flight tested in the F-18 High Alpha Research Vehicle. This system consists of a matrix of 25 pressure orifices arranged in concentric circles on the nose of the vehicle to determine angles of attack and sideslip, Mach number, and pressure altitude. During the course of the flight tests, it was determined that satisfactory results could be achieved using a subset of just nine ports.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: SAE PAPER 912142
    Format: text
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  • 5
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    High-angle-of-attack pneumatic lag and upwash corrections for a hemispherical flow direction sensor (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: As part of the NASA F-14 high angle of attack flight test program, a nose mounted hemispherical flow direction sensor was calibrated against a fuselage mounted movable vane flow angle sensor. Significant discrepancies were found to exist in the angle of attack measurements. A two fold approach taken to resolve these discrepancies during subsonic flight is described. First, the sensing integrity of the isolated hemispherical sensor is established by wind tunnel data extending to an angle of attack of 60 deg. Second, two probable causes for the discrepancies, pneumatic lag and upwash, are examined. Methods of identifying and compensating for lag and upwash are presented. The wind tunnel data verify that the isolated hemispherical sensor is sufficiently accurate for static conditions with angles of attack up to 60 deg and angles of sideslip up to 30 deg. Analysis of flight data for two high angle of attack maneuvers establishes that pneumatic lag and upwash are highly correlated with the discrepancies between the hemispherical and vane type sensor measurements.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: NASA-TM-86790 , H-1314 , NAS 1.15:86790
    Format: application/pdf
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  • 6
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    Preliminary results from a subsonic high-angle-of-attack flush airdata sensing (HI-FADS) system - Design, calibration, algorithm development, and flight test evaluation (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A nonintrusive high angle-of-attack flush airdata sensing (HI-FADS) system was installed and flight-tested on the F-18 high alpha research vehicle. This paper discusses the airdata algorithm development and composite results expressed as airdata parameter estimates and describes the HI-FADS system hardware, calibration techniques, and algorithm development. An independent empirical verification was performed over a large portion of the subsonic flight envelope. Test points were obtained for Mach numbers from 0.15 to 0.94 and angles of attack from -8.0 to 55.0 deg. Angles of sideslip ranged from -15.0 to 15.0 deg, and test altitudes ranged from 18,000 to 40,000 ft. The HI-FADS system gave excellent results over the entire subsonic Mach number range up to 55 deg angle of attack. The internal pneumatic frequency response of the system is accurate to beyond 10 Hz.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: AIAA PAPER 90-0232
    Format: text
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  • 7
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    Experimental characterization of the effects of pneumatic tubing on unsteady pressure measurements (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Advances in aircraft control system designs have, with increasing frequency, required that air data be used as flight control feedback. This condition requires that these data be measured with accuracy and high fidelity. Most air data information is provided by pneumatic pressure measuring sensors. Typically unsteady pressure data provided by pneumatic sensing systems are distorted at high frequencies. The distortion is a result of the pressure being transmitted to the pressure sensor through a length of connective tubing. The pressure is distorted by frictional damping and wave reflection. As a result, air data provided all-flush, pneumatically sensed air data systems may not meet the frequency response requirements necessary for flight control augmentation. Both lab and flight test were performed at NASA-Ames to investigate the effects of this high frequency distortion in remotely located pressure measurement systems. Good qualitative agreement between lab and flight data are demonstrated. Results from these tests are used to describe the effects of pneumatic distortion in terms of a simple parametric model.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: NASA-TM-4171 , H-1538 , NAS 1.15:4171
    Format: application/pdf
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  • 8
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    Failure detection and fault management techniques for flush airdata sensing systems (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Methods based on chi-squared analysis are presented for detecting system and individual-port failures in the high-angle-of-attack flush airdata sensing system on the NASA F-18 High Alpha Research Vehicle. The HI-FADS hardware is introduced, and the aerodynamic model describes measured pressure in terms of dynamic pressure, angle of attack, angle of sideslip, and static pressure. Chi-squared analysis is described in the presentation of the concept for failure detection and fault management which includes nominal, iteration, and fault-management modes. A matrix of pressure orifices arranged in concentric circles on the nose of the aircraft indicate the parameters which are applied to the regression algorithms. The sensing techniques are applied to the F-18 flight data, and two examples are given of the computed angle-of-attack time histories. The failure-detection and fault-management techniques permit the matrix to be multiply redundant, and the chi-squared analysis is shown to be useful in the detection of failures.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: AIAA PAPER 92-0263
    Format: text
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  • 9
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    Preliminary results from an airdata enhancement algorithm with application to high-angle-of-attack flight (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A technique has been developed to improve the fidelity of airdata measurements during dynamic maneuvering. This technique is particularly useful for airdata measured during flight at high angular rates and high angles of attack. To support this research, flight tests using the F-18 high alpha research vehicle were conducted at the NASA Ames Research Center Dryden Flight Research Facility. A Kalman filter was used to combine information from research airdata, linear accelerometers, angular rate gyros, and attitude gyros to determine better estimates of airdata quantities such as angle of attack, angle of sideslip, airspeed, and altitude. This paper briefly develops the state and observation equations used by the Kalman filter and shows how the state and measurement covariance matrices were determined from flight data.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: AIAA PAPER 91-0672
    Format: text
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  • 10
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    The effects of pressure sensor acoustics on airdata derived from a high-angle-of-attack flush airdata sensing (HI-FADS) system (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The accuracy of a prototype nonintrusive airdata system derived for high-angle-of-attack measurements was demonstrated for quasi-steady maneuvers as great as 55 degrees during phase one of the F-18 high alpha research vehicle flight test program. This system consists of a matrix of nine pressure ports arranged in annular rings on the aircraft nose, and estimates the complete airdata set utilizing flow modeling and nonlinear regression. Particular attention is paid to the effects of acoustical distortions within the individual pressure sensors of the HI-FADS pressure matrix. A dynamic model to quantify these effects which describes acoustical distortion is developed and solved in closed form for frequency response.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: AIAA PAPER 91-0671
    Format: text
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