Variation in load experience: A re-analysis of Fokker F27 and Foker F28 operational acceleration data

Fatigue meter data obtained during operational flights of Fokker F27 and Fokker F28 aircraft were re-processed and analyzed to study the variation in load experience between different aircraft of the same type. The Data covered about 470000 flights, made by 101 aircraft of 51 different operators. A simple algorithm was developed to quantify the...

Worst case gust shapes for atmospheric turbulence with known spectrum

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.

Atmospheric turbulence spectra and correlation functions

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...

Definition of P.S.D.-design loads for nonlinear aircraft

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...

The generation of a random process with a spectrum with fractional power

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.

Estimation of load exceedances of an aircraft undercarriage with nonlinear properties excitated by random runway unevenness

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...

Historical development of collision risk models for en-route air traffic

This lecture reviews the model studies that were made with the object to reduce en-route separation standards. It also describes the basic principles of the Reich model used in most of these studies and of the Minimum Navigation Performance Specification (MNPS). Paper presented at the Princeton University Conference 155, "Safety Issues in Air...

Vertical accelerations of a large aircraft during landing and taxiing

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.

The determination of gustloads on nonlinear aircraft using a Power Spectral Density approach

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...

Some methods for the derivation of taxying loads for undercarriages with linear or nonlinear properties.

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.

Aircraft design loads due to non-stationary atmospheric turbulence patches

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...

Wind shear on the approach: An investigation on the infuence of a tower measured wind environment on the symmetric motions of a simulated aircraft in an automatic approach

Measured wind profiles from the Royal Netherlands Meteorological Institute 200 m meteorological tower at Cabauw have been used to estimate wind shear effects on the symmetric motions of an approaching aircraft. Wind profiles as well as an automatically approaching DC-9 aircraft have been simulated on an electronic analog computer. The study...

Exploratory investigation of decelerating approaches of a twin-engined jet transport: Vol. II: Moving-base simulation and comparison with related experiments

Aircraft noise perceived on the ground can be reduced by decelerating the aircraft during the landing approach. As an additional benefit the lower thrust settings existing during a part of the approach and the shorter approach time result in a reduced fuel consumption as compared to a conventional approach. This report deals with an experiment...

Digital filtering methods, with applications to satellite attitude determination in the presence of modelling errors. Part I: theory

The report reviews a number of digital filtering methods and gives examples of their application. The methods include batch processing methods and rec\irsive methods, not only in the classical formulations but also in square-root formulations. The latter formulations have the purpose to prevent certain numerical inconveniences. Much attention is...

Equations for the response of an airplane to non-stationary atmospheric turbulence patches

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...

Comparison between the statistical discrete gust method and the power spectral density method

The Power Spectral Density method and the Statistical Discrete Gust Method to calculate aircraft design loads due to atmospheric turbulence are compared qualitatively and quantitatively on the basis of the load exceedance curves for certain aircraft models. It is shown that both methods are related to each other, giving the same results for...

Simulation of the automatic approach of a twin-engined jet transport

In order to obtain insight in the accuracy of automatic approaches, the symmetric motions of an aircraft, stabilized by autopilot and autothrottle, are simulated on an electronic analog computer. The aircraft tracks an I.L.S. glide path, being disturbed by I.L.S. beam bends, atmospheric turbulence and wind shear. The deviations of the aircraft...