For an augmented aircraft, it is shown that filter error method leads to improved identifiability of aerodynamic parameters from measurements that are affected by the feedback from the flight controller. Simulated lateral-directional data of an advanced fighter aircraft, obtained from a nonlinear six-degree-of-freedom simulator, are used for the purpose of analysis. The aircraft stability and control derivatives are estimated using filter error method and compared to the estimates obtained from output error method to ascertain the degree of improvement achieved in the identified derivatives. Identification results with output error method show that feedback causes a discernible offset in the estimated values of the derivatives relative to the reference parameter values. The filter error method helps to reduce this offset and thereby yield estimates that match better with the reference parameter values.

The turn of the century produced the expected crop of articles listing space achievements over the past 30-40 years. Many of them, particularly those connected with the Moon landing, made the front pages of newspapers all over the world, and are still regularly served up in television programmes. Nevertheless, they constitute an inadequate basis on which to make an assessment as to where — if the expression can be permitted — we now stand in space. It is no longer sufficient to look at progress in the individual space segments: satellites, launchers and the often neglected ground segment. The springs of action are now to be found elsewhere: the uptake of space applications by the end-users (most of whom have no knowledge of, or interest in, space); the increasing role of the private sector in financing space systems; the inter-twining of the civilian and defence programmes; political and international trade considerations, etc. This.article is an attempt to review progress against the background of these external factors and to present a balance sheet. In order to leave posterity with further palpable proof of the author's fallability, the article will close with a few thoughts on future trends and technological developments.

Although small in comparison with some other global activites, civil and military space operations account for about $50bn annually. Of this, slightly less than 10% can be identified as European, compared to just over 50% for the United States. This volume has been stable for several years and promises to continue at least for the near future, although the distribution between the various sectors is changing. Space is therefore an activity of considerable importance to public and private sectors alike, even though it has lost its high place on the political agendas of many countries.

This paper investigates the potential benefits of utilising bifurcation analysis results in the planning and evaluation of piloted simulator trials of manoeuvrable aircraft, particularly when encountering nonlinear phenomena such as departure. Comparisons of bifurcation diagram predictions with piloted simulations are performed in order to validate the technique for application to realistic flight conditions. A close relationship is found between the theoretical and the experimental responses, and potential improvements in effectiveness of piloted test programmes are identified. Proposals for enhancing the predictive capability of bifurcation methods are made.

Various control options, using both conventional and novel control motivators, may be available to the designer of a second-generation supersonic commercial transport (SCT) aircraft. A number of tradeoff studies using conventional control surfaces have already been addressed and, more specifically, the low-speed performance benefits deriving from a second pitch control surface quantified. However, a combination of limited rudder control power together with the continuing need to improve overall aircraft performance through reduced fin and control surface sizing has resulted in this assessment of alternative methods of control power generation. Specifically, using the foreplane asymmetrically to generate yawing moments for directional control and deflecting the engine exhaust nozzles for thrust vector control (TVC) about all three rotational axes. At low-speed the effectiveness of TVC will be enhanced due to the high engine thrust required by an SST to overcome the large lift-induced drag generated at approach angles of attack where, conversely aerodynamic control power will be at a minimum due to low dynamic pressure.

This paper begins with a statement of the technical background to the work together with an overview of TVC and its current applications. This is followed by a description of the aerodynamic mathematical model, thrust vector control implementation and the accompanying flight control system. A comparison of aerodynamic and thrust vector control at low speed is then made using established manoeuvres about all three rotational axes. Aircraft speed, take-off performance and the effect of fin area reduction are also addressed. Finally, the major results are summarised and conclusions drawn on a selection of control options and the associated implementation issues. It should be noted that issues relating to high speed and supersonic cruise are not specifically addressed nor are the implications of engine failure conditions.

Exact expressions for the frequency equations and mode shapes of an idealised whole aircraft are derived using the symbolic computation package REDUCE. The aircraft is idealised as a bending-torsion coupled beam for the wing with the associated mass and inertia of the fuselage, tail-plane, fin and rudder assembly being concentrated at the root. The governing differential equation of motion of the aircraft is then solved in its most general form. The analysis is split into symmetric and anti-symmetric cases to formulate the equations from which the natural frequencies and the corresponding mode shapes of the unrestrained aircraft are derived. The analytical approach used here is of great significance, particularly from an aeroelastic optimization point of view, for which repetitive calculations of natural frequencies and mode shapes are often required. The application of the theory is demonstrated by numerical results. These results have been compared with those obtained from the dynamic stiffness and finite element methods.