A MATLAB program to study gust loading on a simple aircraft model

The present report is part of a "Manual" on aircraft loads, that is being prepared by NLR. It contains a computer program, to be used in combination with "MATLAB4 for Windows" (Student Edition) software, to study aircraft loading due to turbulence. It includes a simple aircraft response model with two rigid and three flexible symmetric degrees...

Some aspects of aircraft response to atmospheric turbulence

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.

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.

The deterministic power-spectral-density-method for nonlinear systems

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 ...

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.

An introductory course on aircraft loading

The present course book has been prepared as lecture notes for a summer course given at the Technical University of Bandung (ITB) in the summer of 1984. This course took place within the framework of the TTA-79 Technical Assistance Project as agreed between the Governments of Indonesia and the Netherlands. The subjects of the course are listed...

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...

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...

A non-stationary model for atmospheric turbulence patches, for the prediction of aircraft design loads

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...

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...

Investigation on a passenger ride-comfort improvement system with limited control surface actuator performance for a flexible aircraft

For the low wing-loading aircraft, considered in this investigation, vertical acceleration appeared to be an important factor concerning passenger comfort. To reduce vertical motions, a ride-comfort improvement system was introduced. Determination of parameters of the system, like gains and allowable performance limitations, required analog...

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...