Aircraft Design最新文献

This paper concerns the development of a failure management software for use in a Flush Air Data System (FADS). FADS is used for the online computation of air data parameters namely, Mach number, angle of attack and angle of side slip. Failure management, an essential requirement for FADS, especially in the context of aircraft flight control applications, has been addressed using a novel concept called failure indicator vector. This new methodology ensures the selection of correct values out of a number of redundant values of a computed air data parameter. This method leads to symbolic processing techniques, which is found to be very effective in terms of programming efficiency and simple procedure for logical reasoning. The method and the software have been successfully tested using the wind tunnel data generated at NAL.

Traditionally, one of the priority directions in TsAGI's research activity is searching for new concepts in the field of aviation technologies. In the context of these studies basic problems related to the development of advanced large-capacity aircraft of a flying-wing (FW) configuration have been studied at TsAGI since the late-1980s (Symposium on “Aeronautical Technology in XXI Century”, Moscow, September 1989; Conceptual design for passenger airplane of very large capacity in “flying wing” layout, ICAS 96-4.6.1, 1996). In the present paper primary emphasis is placed on the rationale of selecting FW main design solutions, aerodynamic configuration, structural concept as well as on development and analysis of alternative configurations. Consideration is also given to the problem, which is in the opinion of experts the most critical for this airplane type, namely, meeting FAR-25 standards with respect to airplane operation in emergency situations. At present the work on this concept is being conducted under the International Scientific and Technical Center grant No. 548. The project collaborators are AIRBUS INDUSTRIE and Boeing.

A method will be described which allows for a uniform approach to determine the specific energy demand of aeroplanes and other vehicle systems. By the introduction of a dimensionless figure, it can be used for comparison irrespective of the very dissimilar definitions. The entity ε, well known from the physics of flight, the glide number—i.e. the inverse of the L/D-ratio in Anglo-American literature—proves to be a convenient starting point.

In order to utilise the primary energy demand as a basis for comparison, further factors have to be taken into consideration and expressed as efficiency levels, as is usual in energy sciences. By doing this, a deep insight will be gained into the different physical and technical elements of transportation processes. Some unexpected results are derived. In particular, the role of the aeroplane has to be adjusted substantially with respect to public opinion.

Due to inefficiencies and associated cost incurred by taxi-in related delays in a busy airport, a new idea has been proposed to efficiently command and control the landing ground run of medium to heavy transport aircraft equipped with thrust reversers. The idea is based on the modulation of thrust reversers installed on the aircraft. To demonstrate the efficiency of such a system, the complete equations of motion as soon as the main gears touch the ground, up until the aircraft comes to a complete stop have been developed. In addition to the thrust reversers, all effective control mechanisms during the landing process, such as brakes and spoilers have been included in the mathematical model. By proposing a suitable definition for an optimum landing ground run and its associated cost function different contour plots for landing ground run vs. optimal control commands have been developed for a typical heavy transport. It is further shown that a modulated thrust reverser could be an effective tool to command and control the landing ground run of an aircraft. The results of simulation program for a typical heavy transport, such as a B-747-100, show a possibility of 12% decrease in the time associated with taxi-in.

Accurate gas turbine performance models based on thermodynamic principles can bring many benefits. In such models it is a normal practice to represent the different components by means of its performance maps or component characteristics describing the relationships between the thermodynamic variables representing the component.

It is well known that the fans of high-bypass engines have strong radial profiles of all thermodynamic variables. It is common to average these profiles so that one or two characteristic maps can represent the fan.

The present paper describes how the radial profiles can be used to make an estimation of turbofan performance. The results are somewhat different to those produced using a component performance maps.

Due to their excellent fatigue characteristics and relatively low density, fiber metal laminates (FML) are considered as candidates for fuselage materials in future generation ultra-high capacity aircraft (UHCA). To exploit the postbuckling behavior, as is the practice in conventional aluminum alloy fuselage structures, an existing engineering design method for postbuckled shear panels was adapted for applications with FML materials. To verify the adapted design methodology, two stiffened FML shear panels were designed and tested until failure. The dimensions of the panels were taken to be representative of an UHCA fuselage structure. In addition, detailed finite element analyses were performed with STAGS to predict panel response during testing. The finite element results showed very good agreement with experimental data, giving confidence in replacing very costly actual panel tests with computer simulations. It was found that the test panel dimensions were outside the region where the current engineering design method for postbuckled panels is valid. To account for this phenomenon, an extension to the current design method is proposed.

A very significant amount of wind energy is contained in the movements of air at high altitudes. A particular invention (Laddermill Patent Ned. 1004508. Nov. 1996 applications Europe and USA), named “laddermill”, is described that allows exploiting this energy using the winds up to possibly the tropopause. A “laddermill” is a self-supporting system that consists of an endless cable connected to a series of high-lifting wings or kites moving up in a linear fashion, combined with a series of low-lifting wings or kites going down. The cable drives an energy generator placed on the ground. Dutch measured wind statistics are presented that show the immense power source at high altitudes. Some general physical considerations are given for the laddermill. Three simulation programmes were developed independently by different institutions. The results give a good consistency of the laddermill shape and power production. Design solutions are indicated for the wing attitude control and stability and a concept for the ground station is presented providing wing and cable handling. Adaptation to weather is given by flexible retrieval and deployment capability. Comparisons are shown with existing wind turbines. An operational model and related cost model have been made that include an operation strategy that optimises the economical effectiveness of the wings, cable and ground station. This operational model has been applied to the actual wind measurements over a period of 10 years. The results show, in comparison to the existing horizontal axes wind turbines, (i) a potential for significantly larger amount of wind energy production and (ii) an indication that this can be done at significantly lower cost. The public acceptance has been assessed, resulting in a positive perception of elegance of the low speed and silent movements combined with the excitement from reaching impressive altitudes. Safety and potential aviation interference are also addressed.

Hybrid laminar flow control (HLFC) is an active drag reduction technique. A delay in transition of the boundary layer from laminar to turbulent flow is usually achieved by the application of suction over the first 10–20% of the chord. The design of the suction surface and the chambers underneath the perforated skin represents one of the most significant engineering challenges concerning HLFC. A review of design requirements, candidate materials and drilling methods for the production of the suction surface, is presented. Materials considered include titanium, aluminium and carbon fibre composite. Laser (Excimer or Nd–YAG) and electron beam drilling has been used to produce satisfactory suction panels.