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  • 1
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    Analysis of the nature and cause of turbulence upset using airline flight records (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The development and application of methods for determining aircraft motions and related winds, using data normally recorded during airline flight operations, are described. The methods are being developed, in cooperation with the National Transportation Safety Board, to aid in the analysis and understanding of circumstances associated with aircraft accidents or incidents. Data from a recent DC-10 encounter with severe, high-altitude turbulence are used to illustrate the methods. The analysis of this encounter shows the turbulence to be a series of equally spaced horizontal swirls known as 'cat's eyes' vortices. The use of flight-data analysis methods to identify this type of turbulence phenomenon is presented for the first time.
    Keywords: AIR TRANSPORTATION AND SAFETY
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  • 2
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    A mathematical model for efficient estimation of aircraft motions (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: In the usual formulation of the aircraft state-estimation problem, motions along a flight trajectory are represented by a plant consisting of nonlinear state and measurement models. Problem solution using this formulation requires that both state- and measurement-dependent Jacobian matrices be evaluated along any trajectory. In this paper it is shown that a set of state variables can be chosen to realize a linear state model of very simple form, such that all nonlinearities appear in the measurement model. The potential advantage of the new formulation is computational: the Jacobian matrix corresponding to a linear state model is constant, a feature that should outweigh the fact that the measurement model is more complicated than in the conventinal formulation. To compare the modeling methods, aircraft motions from typical flight-test and accident data were estimated, using each formulation with the same off-line (smoothing) algorithm. The results of these experiments, reported in the paper, demonstrate clearly the computational superiority of the linear state-variable formulation. The procedure advocated here may be extended to other nonlinear estimation problems, including on-line (filtering) applications.
    Keywords: AIRCRAFT STABILITY AND CONTROL
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  • 3
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    Identifiability of unknown noise covariance matrices for some special cases of a linear, time-invariant, discrete-time dynamic system (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Two off-line schemes are proposed for the identification of unknown noise covariance matrices Q and R of a discrete-time dynamic system. The first scheme is based on a maximum a posteriori cost function utilizing smoothed state estimates, while the second is based on a maximum likelihood cost function utilizing filtered state estimates. Sensitivity of the cost functions to Q and R is analyzed for the following cases: (1) single-input single-output systems; (2) multiinput single-output systems; and (3) single-input multioutput systems with a diagonal R. Identifiability criteria are presented for the cases considered and demonstrated by examples.
    Keywords: CYBERNETICS
    Type: IEEE Transactions on Automatic Control; AC-26; Aug. 198
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  • 4
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    Analysis of general aviation accidents using ATC radar records (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 19, p. 2973, Accession no. A82-39091
    Keywords: AIR TRANSPORTATION AND SAFETY
    Type: (ISSN 0021-8669)
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  • 5
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    Applications of state estimation in aircraft flight-data analysis (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper traces the evolution of the use of state estimation in the analysis of aircraft flight data and discusses some recent applications associated with airline turbulence upsets and high-angle-of-attack flight tests. A unifying mathematical framework for state estimation is reviewed, and several examples are shown that illustrate a general approach for estimating variables that are difficult to measure. It is hoped that the diversity of the applications discussed and the examples presented will make the flight-data analyst mindful of the potential advantages of using state estimation methods.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 83-2087
    Format: text
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  • 6
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    Blade loss transient dynamics analysis with flexible bladed disk (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The transient dynamic response of a flexible bladed disk on a flexible rotor in a two rotor system is formulated by modal synthesis and a Lagrangian approach. Only the nonequilibrated one diameter flexible mode is considered for the flexible bladed disk, while the two flexible rotors are represented by their normal modes. The flexible bladed disk motion is modeled as a combination of two one diameter standing waves, and is coupled inertially and gyroscopically to the flexible rotors. Application to a two rotor model shows that a flexible bladed disk on one rotor can be driven into resonance by an unbalance in the other rotor, and at a frequency equal to the difference in the rotor speeds.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-168176 , NAS 1.26:168176
    Format: application/pdf
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  • 7
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    Blade loss transient dynamic analysis of turbomachinery (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Previously cited in issue 17, p. 2687, Accession no. A82-34982
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: (ISSN 0001-1452)
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  • 8
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    Equations for determining aircraft motions for accident data (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Procedures for determining a comprehensive accident scenario from a limited data set are reported. The analysis techniques accept and process data from either an Air Traffic Control radar tracking system or a foil flight data recorder. Local meteorological information at the time of the accident and aircraft performance data are also utilized. Equations for the desired aircraft motions and forces are given in terms of elements of the measurement set and certain of their time derivatives. The principal assumption made is that aircraft side force and side-slip angle are negligible. An estimation procedure is outlined for use with each data source. For the foil case, a discussion of exploiting measurement redundancy is given. Since either formulation requires estimates of measurement time derivatives, an algorithm for least squares smoothing is provided.
    Keywords: AIR TRANSPORTATION AND SAFETY
    Type: NASA-TM-78609 , A-7913
    Format: application/pdf
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  • 9
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    Identification of vortex-induced clear-air turbulence using airline flight records (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The nature and cause of clear-air turbulence is being investigated, in cooperation with the National Transportation Safety Board, using the flight records available from airline encounters with severe turbulence. This paper presents two case studies of severe turbulence which indicate that the airplanes involved encountered vortex arrays which were generated by destabilized wind-shear layers near the tropopause. In order to identify and analyze vortex patterns (i.e., vortex strength, size, and spacings), potential-flow models of vortex arrays were developed that describe reasonably well the wind patterns derived from the airliner flight records. The results of this analysis indicate that in the two cases studied, the vortex cores had diameters in the range of 900 to 1,200 ft with tangential velocities in the range of 70 to 85 ft/sec. This study presents the first identification and analysis of vortex arrays from airline flight data. The results are compared with theoretical predictions and previous observations.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: AIAA PAPER 84-0270
    Format: text
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  • 10
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    Blade loss transient dynamics analysis, volume 2. Task 2: Theoretical and analytical development. Task 3: Experimental verification (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The component element method was used to develop a transient dynamic analysis computer program which is essentially based on modal synthesis combined with a central, finite difference, numerical integration scheme. The methodology leads to a modular or building-block technique that is amenable to computer programming. To verify the analytical method, turbine engine transient response analysis (TETRA), was applied to two blade-out test vehicles that had been previously instrumented and tested. Comparison of the time dependent test data with those predicted by TETRA led to recommendations for refinement or extension of the analytical method to improve its accuracy and overcome its shortcomings. The development of working equations, their discretization, numerical solution scheme, the modular concept of engine modelling, the program logical structure and some illustrated results are discussed. The blade-loss test vehicles (rig full engine), the type of measured data, and the engine structural model are described.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165373-VOL-2 , R81AEG381-VOL-2
    Format: application/pdf
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