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The current state of the art of flight flutter testing is reviewed, and areas where this part of the certification procedure could be improved are discussed. It is argued that the key towards speeding up the flight flutter test procedure, and also to reduce costs, is to reduce the number of flight test points that are required as part of the test clearance programme. To achieve this aim, the entire modelling and testing procedure needs to be improved, particularly with respect to non-linearities. Non-linear aeroelastic phenomena will then be able to be predicted more accurately. Current work in a number of relevant technologies is considered in relation to flight flutter testing. Suggestions are made as to how these aspects could be improved in order to speed up and reduce the cost of flight flutter testing, while maintaining, if not improving, the levels of safety., Presented at RTO Applied Vehicle Technology Panel (AVT) Symposium held in Paris, France on 22-25 Apr 2002. The original document contains color images. ISBN 92-837-0027-9. Text in English; p43-1/43-13. This article is from ADA415759 Reduction of Military Vehicle Acquisition Time and Cost through Advanced Modelling and Virtual Simulation (La reduction des couts et des delais d'acquisition des vehicules militaires par la modelisation avancee et la simulation de produit virtuel)

This report results from a contract tasking University of Manchester as follows: The contractor will investigate using a variable stiffness vertical tail attachment to control aeroelastic performance over a range of dynamic pressures. The contractor will (1) Develop an adaptive stiffness attachment for vertical tail aircraft; (2) Develop an analytical model of the attachment and predict aeroelastic performance; (3) Design build and test a vertical tail model with and without a rudder to demonstrate the concept and validate the theoretical predictions; and (4) Conduct wind tunnel testing at sub and supersonic Mach Numbers; and (5) Consider the extension of the design for full-size aircraft and to quantify the benefits., The original document contains color images.

This report results from a contract tasking University of Manchester as follows: A generic all-movable vertical tail will be designed (at the conceptual design level) with conventional and with active flexible technologies. The weight, performance and observable benefits of such designs will then be determined relative to the conventional design. The work will examine a range of different parameters including: Mach number both sub and supersonic speeds, attachment position, yaw stiffness. The optimization will be carried out using either the La Grange code, which is already available at the University of Manchester, or the ASTROS code. A Finite Element model for a generic fin is available which was used in the DASA La Grange optimization code. This model was modified previously for the USAF-ASTROS optimization code. Part of the outcome of this work will be defining the best approach to use such multidisciplinary design and optimization codes to achieve an optimal aeroelastic design. This report results from a contract tasking University of Manchester as follows: A generic all-movable vertical tail will be designed (at the conceptual design level) with conventional and with active flexible technologies. The weight. performance and observable benefits of such designs will then be determined relative to the conventional design. The work will examine a range of different parameters including: Mach number - both sub and supersonic speeds. attachment position. yaw stiffness. The optimization will be carried out using either the La Grange code. which is already available at the University of Manchester. or the ASTROS code. A Finite Element model for a generic fin is available which was used in the DASA La Grange optimization code. This model was modified previously for the USAF-ASTROS optimization code. Part of the outcome of this work will be defining the best approach to use such multidisciplinary design and optimization codes to achieve an optimal aeroelastic designc

The characterisation of the behaviour of nonlinear aeroelastic systems has become a very important research topic. Nevertheless, most of the work carried out to date concerns the development of unsteady CFD solutions in the transonic region. Important though this work is, there is also a need for research which aims at understanding the behaviour of nonlinear systems, particularly the occurance of Limit Cycle Oscillations (LCOs). The purpose of this paper is to study the stability of a simple aeroservoelastic system with nonlinearities in the control system. The work considers both structural and control law nonlinearities and assesses the stability of the system response by use of bifurcation diagrams. It is shown that simple feedback systems designed to increase the stability of the linearised system also stabilise the nonlinear system, although their effects can be less pronounced. Additionally, a nonlinear control law designed to limit the control surfaces pitch response was found to increase the flutter speed considerably by forcing the system to undergo limit cycle oscillations instead of fluttering. Finally, friction was found to affect the damping of the system but not its stability, as long as the amplitude of the frictional force is low enough not to cause stoppages in the motion., Presented at the Specialists' Meeting of the RTO Applied Vehicle Technology Panel (AVT) held in Ottawa, Canada, 18-20 Oct 1999. This article is from ADA388195 Structural Aspects of Flexible Aircraft Control (les Aspects structuraux du controle actif et flexible des aeronefs)

This report results from a contract tasking School of Engineering University of Manchester as follows: The contractor will investigate improvements in excitations signals used in aircraft flutter flight test data collection. It describes the work done during the period 1 April - 30 September 1998 for the EOARD contract F61775-98-WEO12 on Improved Flight Flutter Testing Excitation Techniques. Strategies. A number of improved swept sine (Chirp') and random excitation signals are developed and demonstrated to be superior to conventional linear sweeps and minimum crest factor random signals.