Aircraft Design最新文献

This paper describes the results of a study where an on-line parameter identification (PID) technique is used for determining on-line the mathematical model of an aircraft that has sustained damage to a primary control surface. The mathematical model at post-failure conditions can then be used by a failure accommodation scheme to compute on-line the compensating control signal to command the remaining healthy control surfaces for a safe continuation and/or termination of the flight. Specific criteria for the use of an on-line PID for these critical flight conditions are first discussed. The methodology is illustrated through simulations of a fighter jet at subsonic flight conditions featuring a novel modeling procedure to characterize the post-failure/damage aerodynamic conditions. The simulations have shown the potential of this on-line PID within a fault tolerant flight control system. The results have also highlighted the importance of conducting an ‘ad hoc’ small amplitude and short-duration PID maneuver immediately following a positive failure detection to enhance the reliability of the on-line estimated parameters used in the accommodation scheme.

A new methodology has been proposed to control the distribution of mass in an aircraft during the design and development process. Having estimated the total mass, the aircraft is considered to be composed of different segments each with an unknown mass and the equations of motion are derived based on this discritized mass model. A suitable mass distribution is then found based on the desired dynamic and static stability criterion. Using this methodology the aircraft static margin can be controlled by changing the external shape (X_ac) as well as mass distribution (X_cg). By relating all applicable mass moments of inertia to the frequencies and damping ratios of longitudinal and lateral-directional dynamic modes, the chance of designing a well dynamically balanced aircraft in a variety of flight phases is increased. The mathematical procedure can explicitly be derived only for rigid airplanes where two-dimensional approximations are valid. However, numerical algorithms must be used for elastic and/or rigid aircraft with coupled equations of motion. The proposed methodology has been used to find suitable mass distributions for a B-747-100 in a cruising flight while satisfying the Level-I flying quality requirements.

Handling qualities of airplanes can be improved by the use of an automatic control system (augmented stability control system), however, in the preliminary design phase it is sometimes better to implement suitable design changes. These changes can be performed according to iterative and trial–error procedures in order to get the required flight qualities. In the present paper a different approach to improve lateral handling qualities of aircraft is followed, based on necessary and sufficient conditions for the roots of the lateral characteristic equation to lie in prescribed region of the complex plane. As a result of this study, handling quality region of levels 1–3 can be visualized in the space of the physically relevant parameters. As an example, the vertical tail surface S_v and the dihedral angle Γ are chosen and the regions of levels 1–3 corresponding to some aircraft are shown in the ($\text{S}{}_{\mathrm{<mtext>v</mtext>}}\text{,}\text{Γ}$) plane.

In this paper, a number of numerical and experimental tools developed at our Department (Dipartimento di Progettazione Aeronautica from here on called DPA) and devoted to aircraft design for low subsonic flow will be presented and summarized. These tools comprise numerical codes for analysis, design and simulation, and experimental tests performed in our tunnel and particularly devoted to light aircraft design. The importance of developing such tools in house will be highlighted. Examples of light aircraft designed using such tools will be presented and some attention will be paid to the design of a three-surface R/C model aircraft and on the adaptation of numerical codes to the prediction of its behaviour in the non-linear range of angles of attack.

The value of teaching aircraft design at university by means of student design projects is explored. It is argued that conceptual design is an essential part of engineering education and it provides a foundation for the development of engineering judgement, which is required to establish a balance between safety, economics and functionality of an engineering system. The design process is constituted by two elements – a creative process involving the postulation of design alternatives, and an analytical process, which evaluates the envisaged designs. Detail design teaches vocational skills and instils an awareness of the complex, multidisciplinary and integrated nature of the aeronautical engineering business. The factors that limit the quality of design education include: support staff, time, financial resources, teamwork and lecturing staff.

In this paper the experience of the author in running a flight dynamics course with MATLAB computer assignments as a large part of the course and the sole means of assessment is discussed.

Critical reviews made by various organisations on both sides of the Atlantic have identified the need for continuing changes in engineering teaching curriculum, emphasising inclusion of more intense design education to meet the requirements of industry. The concept of this paper outlines introducing design education within aerospace engineering in an integrated approach involving industries, universities, regional technical colleges and vocational institutes to produce a marketable ab initio trainer aircraft. The task involves conceptual studies, design, analysis and testing of the aircraft through course assignments. The aircraft is to be certified and manufactured by a participating industry also responsible for product liability. By combining the educational programmmes of university students and industrial apprentices, the bulk of manpower can be obtained free with quality of workmanship sufficient for prototyping (preproduction aircraft) assured through strict supervision by experienced personnel from both academia and industry. An innovative management set-up, modelled as a ‘Virtual Company’, is proposed as an organisational structure to execute the project. The success of the proposition depends primarily on planning and co-ordination of the project. The crux of the progress hinges on the availability of hi-tech resources from industry and attitude changes in the teaching establishments. The benefits are the output from institutes who have acquired the analytical capabilities and trade skills along with the opportunities to acquire those traits of creative synthesis and judgement required by the industry, while producing a marketable product with no development cost to be amortised in the selling price (more than 15% price reduction possible).