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Noback, R. (author)
Aspects of the requirements for and the calculation of design loads due to atmospheric disturbances are discussed. Special attention has been paid to the relation between discrete gusts and continuous turbulence. It is recommended that a worst case gust model, as described in this report, be further developed.
report 1993
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Noback, R. (author)
A worst case gust shape has been derived for turbulence or gust patches, assuming only that the average spectrum of such patches is known. The maximum value of the response can be calculated quite easily. The result differs from the PSD-method. Some examples of worst case inputs and outputs are given, also for nonlinear systems.
report 1993
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Noback, R. (author)
The Deterministic Power-Spectral-Density method can be derived from the Design Envelope Analysis of the continuous P.S.D.-method. It provides a method to determine a deterministic function that gives a maximum response equal to the P.S.D.-design load for linear systems. The P.S.D.-design load is undefined for nonlinear systems. In this report a ...
report 1992
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Noback, N. (author)
The Deterministic Power-Spectral-Density-method has been derived directly from the continuous P.S.D.-method. It can be regarded as a "translation" from the frequency domain to the space or time domain. The critical gust profile, giving maximum response, is obtained directly. The D.P.S.D.-method gives the same results as the continuous P.S.D.-...
report 1992
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Noback, R. (author)
Equations for the response of an aircraft to two-dimensional vertical atmospheric turbulence have been derived, both for an aircraft regarded as a continuous system and for an aircraft split up into a number of panels. These equations have been applied to an aircraft model with two degrees of freedom of the size of the Fokker 100, respectively....
report 1991
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Noback, R. (author)
The derivation of one- two- and three-dimensional spectra and correlation functions for isotropic (atmospheric) turbulence and the mutual relations have been collected from various sources. Aircraft loads usually are determined using a one-dimensional turbulence description. In some cases a two- or even three-dimensional description might be...
report 1989
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Noback, R. (author)
The Power Spectral Density (P.S.D.)-method is used to define design loads due to atmospheric turbulence. The design loads are calculated using linear transfer functions. These methods can not be used if the equations describing the behaviour of the aircraft are nonlinear. One method to define design loads for a nonlinear aircraft is by means of...
report 1989
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Noback, R. (author)
A method is described to generate a random Gaussian process with a power spectrum with fractional power, for example the von Karman spectrum for atmospheric turbulence. The method uses digital filtering of a white noise process and it is based on the use of fractional derivatives. An algorithm to generate the process is presented.
report 1988
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Noback, R. (author)
Measured time histories of atmospheric turbulence have been analysed. Distribution functions and exceedance curves of the turbulence and its derivative are presented. The load exceedance curves of various mathematical airplane models due to these turbulence patches have been calculated. Deviations of the properties of these patches from the...
report 1988
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de Jonge, J.B. (author), Noback, R. (author), van der Wekken, J.J.P. (author)
Since more than ten years, service load data, including e.g. acceleration peaks, recorded in B747 aircraft have been stored at NLR in the so-called AIDS-Fatigue Data Base. This paper describes the procedures applied to reduce the acceleration date to "delivered gust velocities". The results are presented and compared with other data sources. The...
report 1986
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Noback, R. (author)
This report gives an outline of the method to generate equal probility design load conditions. The various steps are described.
report 1985
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Noback, R. (author)
A method is derived to generate consistent sets of design load conditions if aircraft design loads are determined using the Design Envelope criterion of the Power Spectral Density (P.S.D.)-method. The method is based on the use of the correlation coefficients between the various loads. Two sets of design load conditions have special properties...
report 1985
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Noback, R. (author)
In this report various methods to describe a landing gear with nonlinear properties and excitated by random runway unevenness during taxying have been investigated. The results of calculations have been compared to measured results from an analog computer simulation. The mean behaviour, standard deviations and power spectra, can be described...
report 1984
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Noback, R. (author)
Historical reviews of the discrete gust and the continious gust concept, in relation to the present requirements, are given in this report. A comparison is made between the discrete gust method and the power spectral density method on the basis of simple airplane models. No direct relation between the two methods exists. The main cause of the...
report 1982
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Noback, R. (author)
Vertical accelerations diiring landing and taxiing have been extracted from the AIDS-data base. This data base contains fatigue related data derived from the AIDS-system, used by KSSU-Boeing 747 operators. Results are presented axid compared with similar data from other sources.
report 1982
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Noback, R. (author), Blaauboer, C. (author)
Design loads for nonlinear aircraft, i.e. aircraft with gust alleviation system or yaw dampler, cannot be established with the Power Spectral Density method. The only method available is by means of computer simvilation. Methods to approximate load exceedance curves of nonlinear aircraft are proposed in this report. For the derivation of the...
report 1980
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Noback, R. (author)
Methods that are used or probably could be used for the establishment of taxying loads are presented and discussed. The methods are straightforward for undercarriages with linear properties. For undercarriages with nonlinear properties methods based on the use of equivalent gains are promising, but still have to be verified.
report 1980
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Noback, R. (author)
In this report it is assumed that atmospheric turbulence appears in patches and that within the patches the turbulence can be described.as a modulated Gaussian process. The patch lengths have a certain probability density function. Load exceedance curves and design loads for various aircraft models for this turbulence model are compared with...
report 1978
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Noback, R. (author)
In this report a model for atmospheric turbulence is proposed. It is assumed that atmospheric turbulence appears in patches and that within the patches the turbulence can be described as a modulated Gaussian process. Statistical properties of this model and of atmospheric turbulence are compared. Using data from various sources a probability...
report 1976
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Noback, R. (author)
In this report a method is described to calculate the load exceedance curve for a linear system having a finite, modulated Gaussian process as input. The derivation is based on the use of ensemble averages, defined as the expected values at a certain point of time. The equations can be used for any airplane-transfer function for which the Power...
report 1976
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