Michael Amprikidis

Development of moving spars for active aeroelastic structures

This paper describes a research program investigating the development of “moving spars” to enable active aeroelastic control of aerospace structures. A number of different concepts have been considered as part of the EU funded Active Aeroelastic Aircraft Structures (3AS) project that enable the control of the bending and torsional stiffness of aircraft wings through changes in the internal aircraft structure. The aeroelastic behaviour, in particular static deflections, can be controlled as desired through changes in the position, orientation and stiffness of the spars. The concept described in this paper is based upon translational movement of the spars. This will result in changes in the torsional stiffness and shear centre position whilst leaving the bending stiffness unaffected. An analytical study of the aeroelastic behaviour demonstrates the benefits of using such an approach. An experimental investigation involving construction and bench testing of the concepts was undertaken to demonstrate its feasibility. Finally, a wind tunnel test of simple wing models constructed using these concepts was performed. The simulated and experimental results show that it is possible to control the wind twist in practice.

Development of An Adaptive Stiffness All-Moving Vertical Tail

An investigation into the aeroelastic characteristics of a wind tunnel model all-movable vertical tail with variable attachment position and stiffness has been made. An initial analytical study investigated the effect of varying the torsional stiffness and position of the single root attachment. An attachment was designed and manufactured that enabled an existing wind tunnel model to behave as an all-moving fin in order to validate the analytical results. This initial study showed that in order to get the full benefits of such a design, whilst still meeting aeroelastic constraints, the torsional stiffness must be adaptive so that it can be adjusted at different regions of the flight envelope. A further variable stiffness attachment was then designed and manufactured that enabled fully adaptive torsional stiffness control. Bench-top tests were performed to validate the structural behaviour of the models, followed by wind tunnel tests to examine the aeroelastic characteristics of the vertical tail models, in particular the aeroelastic effectiveness. The experimental results compared well with theoretical predictions. It was shown that it is possible to control the torsional stiffness, and hence the aeroelastic characteristics, of the all-moving vertical tail using the adaptive stiffness devi ce.

On the Use of Adaptive Internal Structures For Wing Shape Control

This paper describes part of a research programme investigating the dev elopment of “adap tive intern al structures” concepts to enable active aeroelastic control of aerospace structures. A number of different concepts have been considered as part of the EU funded Active Aeroelastic Aircraft Structures (3AS) project that allow the bending and torsional stiffness of aircraft wings to be controlled through changes in the internal aircraft structure. The aeroelastic behaviour, in particular static bending and twist deflections, can be controlled through changes in the posit ion, orientation and stiffness of the spars. In this paper, finite element models ar e used to explore the use of rotating spars to vary structural stiffness, thus adjust ing the static aeroelastic wing twist and bending shape, and thus altering the lift an d drag properties . The effect on the flutter characteristics is also explored. A number of experimental studies of the concepts are also described.

Development of An Adaptive Stiffness Attachment For an All-Moving Vertical Tail

An investigation is described into the design, manufacture and testing of an all-moving vertical tail wind tunnel model with adaptive torsional stiffness attachment. Of particular interest is the use of pneumatic devices to create the adaptive stiffness attachment. A number of bench -tests are described examining the relationship between the pressure in the cylinders and the resulting torsional stiffness. Following modal testing of the vertical tail with adaptive attachment, a series of wind tunnel tests were performed examining the static and dynamic aeroelastic behaviour. Comparison was made with computational predictions and a good agreement was obtained. Further investigations were made into the freeplay behaviour of the device and also the best implementation strategy to use.

Development of smart vortex generators

Two concepts for Smart Vortex Generators have been designed, constructed and tested. The first is based upon the use of Shape Memory Alloy, whereas the second makes use of a pneumatic actuator. Experimental wind tunnel tests were undertaken using Fluorine Flow Visualisation in order to investigate their performance. It was demonstrated that both concepts enabled full control of the vortex generator angle for all speeds up to 35 ms-1.