No description available.

Vertical/Short Take-Off arid Landing (V/STOL) fighter aircraft are characterised by increased control complexity caused by the extra degree ol freedom. This can result in a high pilot workload which may be alleviated with the careful application of active flight control. However, the advent of control configured vehicles demands that the controller design must be part of a fully integrated and iterative aircraft design; hence it must allow the two-way flow of design information. In this thesis a suitable controller design method is developed to solve this two-fold problem. The method is based upon a singular perturbation analysis which is used to expose the underlying dynamics of a closed-loop state-space system. developments are described which allow high-order, dynamically complex parasitics, such as actuators, to be included in the design. Furthermore, the method gives the designer insight into the problem allowing tuning and engineering trade-offs to be performed intelligently with a two-way flow of design information. The end result is a robust high-gain multivariable controller. In order fully to develop arid analyse the method it has been applied to a representative non-linear time-varying aircraft simulation model. This LS supplied by the Royal Aerospace Establishment, Bedford. The necessary slate-space matrices are otitairted by lirLearisirig the model at several different flight cases. This occurs over a wide flight envelope, from hover to 300 Kts, and consequently the multivariable control laws are implemented using gain scheduling. Finally, task tailored control and handling qualities requirements are derived for a V/STOL aircraft in the form of a design brief. This design brief is then fulfilled by designing a controller which alleviates pilot workload during transitions from jet-borne to fully wing-borne flight (and vice versa).

No description available.

No description available.

No description available.

No description available.

An assessment methodology has been developed for - use during the conceptual/preliminary design phase to quantify the effectiveness of newly designed aircraft. The effectiveness is measured by a squadron Sortie Generation Rate (SGR). Key elements of this methodology were the establishment of link parameters between design synthesis and the main effectiveness disciplines. These were Reliability and Maintainability (R&M), Survivability/Vulnerability and Acquisition Cost. A programmable solid modeller was used to create a solid CAD assembly of the aircraft critical components. A ray tracing technique has been used to develop an interactive vulnerability assessment tool. A Mission Simulation Model (MSM) has been developed which typically simulates the operation of a squadron of aircraft and gives the operational activities such as flying sorties and maintenance actions. The methodology has been validated based on real data from recent conflicts. The application aspects of the methodology have been demonstrated by quantifying the effectiveness of two recent combat aircraft.

This thesis presents the development of a Baseline Configuration for an Advanced Short Take-Off and Vertical Landing (ASTOVL) Combat Aircraft, the Design Synthesis and coding of this Baseline Congiguration (Code VERTI), the interfacing of the Design Synthesis Code VERTI with the Optimizer code RQPMIN and the optimization of the Baseline Configuration. The background and the objectives of this Research Programme are initially examined. The evaluation of the ASTOVL Combat Aircraft Baseline Configuration is then described, including all the problems, assumptions, choices and compromises that led to the specific configuration. The development of the Design Synthesis and the Code VERTI then follow, where the methodology used, the techniques adopted and the code operation are explained. A full description of the Design Synthesis is included as an appendix. Finally, the interfacing of Code VERTI with the optimizer RQPMIN and the optimization of the Baseline configuration are presented. The problems and difficulties of the RQPMIN operation are thoroughly discussed. The RQPMIN- VERTI code is used to optimize the initial Baseline Configuration and an optimization example is provided in appendix form. The optimized Baseline Configuration is partly validated against two ASTOVL combat aircraft designs. In addition to the optimization with the aircraft empty mass as objective function, a search for a better objective function is attempted.

Aerodynamic investigations have shown' that variable camber wings (VCW) for transport aircraft have considerable potential in terms of improving aircraft performance and enhancing their operational flexibility. In order to justify these benefits it is essential that the camber varying system is structurally and mechanically feasible. This research examined the feasibility of providing variable camber to two supercritical aerofoil sections of different'characteristics. The unique method of camber vaTiation was applied by rotating the forward and aft regions of the aerofoil on a circular arc and keeping the surface continuous and matching at their attachment to the main wing box. The change in camber thus increased the chord due to translational motion of the aforementioned regions. The geometries required for varying the forward camber by this method presented formidable design difficulties and no immediate solutions could be found. As a result, an alternative geometry was devised which accepts camber by simply drooping the nose region. A novel idea was developed for aft camber variation, which is considered to be universal for all supercritical aerofoil sections. The system utilises a tracking mechanism which guides a trailing edge element on a continuous arc. Surface continuity is provided by a flexible skin on the upper side and a spring loaded hinged panel on the under side. The flexible skin remains attached to the trailing edge element through a series of roller link arrangement which locate the skin in a separate guide rail. The large moment arm and therefore the increased torsional loads created due to the translational motion of the trailing edge element necessitated investigation of alternative deployment geometries. As a result two additional geometries were schemed. One had reduced radius of rotation and therefore reduced extension, while the other changed camber by drooping the aft region without any chordal extension. Since there was no aerodynamic evidence on the possible benefits offered by these geometries it was decide to postpone them until such information was available. Some detailed aspects of the proposed concept for aft camber variation were considered by applying the system to a modem transport aircraft wing. This resulted in a design which is practically feasible. Justification of this concept was made by designing and testing a half scale structural model of one trailing edge segment. Three dimensional (3-D) geometric investigation showed that the camber-varying elements ride on a frustum of a cone and therefore their deployment is skewed to the line of flight. The 3-D geometric implications of variable camber clearly suggested that the camber variation by rotation on a circular arc, on a tapered wing can be possible if the rotating element is made to flex and twist or it utilises a pin jointed arrangement. To provide the necessary flexibility to the trailing edge element, its structural box best be made from fibre reinforced plastic material. The deployment of the trailing edge element on the structural model was made possible by designing it in laminated wood. Comparison of the proposed variable camber system with a conventional single slotted flap arrangement suggests that the two systems could be equally complex but the variable camber could be slightly heavier., Further systems investigations are required to quantify overall aerodynamic, mass, and cost implications of the use of VCW on transport aircraft.

This thesis investigates the application of Multi-Disciplinary Design, Analysis and Optimisation to the design of a large civil airliner, similar in size as the future A3XX. For the first time structural optimisation, manufacturing cost and aerodynamic effects are simultaneously integrated within a realistic, complex aircraft design problem: the wing box of such a large airliner. A novel multi-level system was developed to incorporate structural effects and manufacturing cost: mass is treated at a top-level while costs are treated at a structural sub-level. It allows a designer to study cost changes with respect to design changes and the interaction of cost with other disciplines such as structures and aerodynamics. The flexibility of the system allows companies to import their own results or cost data and to perform cost studies based on historical data or highly novel processes. Structural optimisation of the wing box using MSc/NASTRAN and STARS, the development of a metal and composite cost model and the overall MDO methodology are being discussed.